Title: The Rise of Marijuana as the Drug of Choice Among Youthful
Adult Arrestees     
Series: Research in Brief
Author: Andrew Golub and Bruce D. Johnson
Published: National Institute of Justice, June 2001
Subject: Drugs and Crime: drug use indicators, Juveniles: juvenile substance abuse
26 pages
64,000 bytes

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U.S. Department of Justice
Office of Justice Programs
National Institute of Justice

National Institute of Justice
Research in Brief
June 2001

The Rise of Marijuana as the Drug of Choice Among Youthful Adult
Arrestees

By Andrew Golub and Bruce D. Johnson

Various surveys have identified a rapid increase in marijuana use during
the 1990s, especially among youths. This raises a variety of questions
about the future of the Nation's drug problems. On one hand, the gateway
theory posits that youthful use of alcohol and/or tobacco and marijuana
tends to precede use of other illicit drugs like crack and heroin (see "The
Gateway Theory"). The recent increase in youthful marijuana use has
fueled speculation that a new epidemic of hard drug abuse may be
imminent [1] and that the burden of drug abuse will be dramatically
increasing in the near future.[2] On the other hand, the start of this new
epidemic coincides with the decline of the crack epidemic. This suggests
that youthful subcultures may have shifted from the destructive nature of
crack abuse to the use of less dangerous drugs.

The recent upsurge in marijuana use is referred to as the New Marijuana
Epidemic to distinguish it from widespread use of marijuana prevailing in
the 1960s and 1970s.[3] This Research in Brief examines trends in
marijuana use detected through urinalysis to track the progress of the
recent epidemic among arrestees at 23 locations across the Nation served
by the Arrestee Drug Abuse Monitoring (ADAM) program--formerly the
Drug Use Forecasting (DUF) program--from 1987 through 1999.

In addition, this report identifies nationwide drug use trends within the
mainstream population on the basis of self-reports of past-month use, a
measure roughly parallel to the length of time in which marijuana can be
detected by urinalysis. Those trends were derived from data collected by
the National Household Survey on Drug Abuse (NHSDA) and Monitoring
the Future (MTF) programs. (See "The Study's Data Sources.")

Overall, study findings suggest the following:

 o Recent increases in youthful marijuana use followed a natural pattern
similar to previous drug epidemics. Use of a particular drug sometimes
follows a wave of popularity: starting from a lull, expanding rapidly,
leveling to a plateau, and subsequently fading away. Prior research with
ADAM/DUF data suggests that the popularity of heroin injection (which
mostly peaked in the 1960s and early 1970s) and crack (which mostly
peaked in the late 1980s) followed this pattern. The current analysis
suggests that the recent wave of marijuana use has followed a similar
pattern so far, although unlike the previous epidemics, the increases in use
were primarily limited to youths.

 o Local differences are important. There were exceptions at a few ADAM
locations to every one of the major regularities in the New Marijuana
Epidemic. Some locations did not observe an epidemic. At other locations,
the epidemic either was not limited to youthful adult arrestees (ages
18-20), expanded more slowly, expanded for a longer period, or was less
prevalent at its peak.

 o In the 1990s, marijuana replaced crack cocaine as the drug of choice
among youthful adult arrestees. Arrestees born since 1970 have been
increasingly likely to be detected as recent marijuana users. Unlike their
predecessors, however, few of them had progressed to crack or heroin by
1998. This provides some evidence to suggest that viewing marijuana as a
gateway drug may be inappropriate for this new generation. Ethnographic
evidence from New York City suggests that use of marijuana by youths
may be associated with strong cultural and subcultural norms that militate
against use of more dangerous drugs.

 o The New Marijuana Epidemic had plateaued by 1996 at most affected
locations and by 1999 at all affected locations. From 1996 to 1999, most
ADAM locations as well as the MTF and NHSDA surveys identified
stable, high levels of recent marijuana use among youths.

 o The New Marijuana Epidemic had a larger impact on youthful adult
arrestees than on youths in the general population. The epidemic in
youthful marijuana use recorded by the MTF and NHSDA programs
started 1 year later, increased more slowly, and was less prevalent at its
peak than the epidemic among youths who tended to get in trouble with
the law as recorded by the ADAM program.

A conceptual model of the New Marijuana Epidemic

Much research suggests that drug epidemics tend to follow a predictable
course. This analysis employs a conceptual model that distinguishes the
characteristics of four phases: incubation, expansion, plateau, and decline.
This model was originally developed to explain the course of the Crack
Epidemic.[4] It has since been used to study the Heroin Injection
Epidemic and has been adapted for the study of the recent increase in
marijuana use.[5] This study found that the dynamics of recent increases in
marijuana use followed a pattern similar to that of the Crack and Heroin
Injection Epidemics, suggesting that all three epidemics were the result of
a comparable diffusion phenomenon.

Theoretically, the passing of each phase of the New Marijuana Epidemic
should result in a distinguishable pattern for the prevalence of marijuana
use detected by the ADAM program, particularly among youthful adult
arrestees and, to a lesser extent, among the overall population of adult
arrestees (ages 18 and older).[6]

Incubation phase. Historical evidence suggests that a drug epidemic
typically grows out of a specific social context; the Heroin Injection
Epidemic grew out of the jazz era [7] and the Crack Epidemic started
among inner-city drug dealers.[8] In both cases, there was an initial
incubation phase during which the new drug-use practice was developed
and nurtured among a relatively small, cohesive group of adult users.
Marijuana use has been widespread since the 1960s; however, the
prevalence of its use had been declining since 1979.[9] During the
incubation phase, the ADAM program would be expected to detect
relatively low levels of marijuana use by adult arrestees, including those in
the youthful category.

Ethnographic research in New York City suggests that the reemergence of
interest in marijuana use was pioneered as part of the youthful, inner-city,
predominately black hip-hop movement.[10] These youths celebrated
marijuana use in their music and on T-shirts. In New York City, they also
preferred to smoke their marijuana in a blunt (an inexpensive cigar whose
contents are replaced with marijuana). The extent to which the New
Marijuana Epidemic outside of New York City is associated with blunt
smoking is not clear. Unfortunately, major national surveys, such as MTF,
NHSDA, and ADAM, do not distinguish among ways of consuming
marijuana. A number of focus groups across the Nation on cigar use [11]
and reports by leading drug abuse experts [12] provide limited (but far
from conclusive) support for the idea that blunt smoking may be a national
phenomenon.

Expansion phase. Eventually, marijuana use spread rapidly as part of a
newly emerging subculture indigenous to youths. In contrast, the Crack
and Heroin Injection Epidemics spread first among adults and only
afterward to youths. This dynamic suggests that the ADAM program
would be expected to detect rapidly increasing marijuana use among
youthful adult arrestees during an expansion phase. The rate of use among
all adult arrestees would be expected to increase more slowly and for a
longer period as members of the New Marijuana Generation aged and
came to constitute a larger portion of the ADAM sample and as the
renewed interest in marijuana diffused to older arrestees.

Plateau phase. Subsequent to its expansion, the New Marijuana Epidemic
could be expected to enter a plateau phase at each ADAM location. During
this period, youths coming of age and getting involved with illegal drugs
would use the current drug of choice, marijuana. During this phase, the
ADAM program would be expected to detect stable and high levels of
marijuana use among youthful adult arrestees and slowly increasing rates
of use overall.

Decline phase. In the 1990s, both the Heroin Injection and Crack
Epidemics were experiencing their decline phases. These drugs have been
much less popular among youths coming of age in the 1990s than among
their predecessors. However, heroin injection and crack smoking are still
quite widespread because many older users have persisted in their habits.
By analogy, when the New Marijuana Epidemic enters a decline phase, the
ADAM program would be expected to detect a rapid decrease in marijuana
use among youthful adult arrestees but a slower, more drawn-out decline
among all adult arrestees.

Results

If data had conformed to the conceptual model described above, the
expansion phase of marijuana use should be readily distinguished by
steady increases in each year (perhaps as large as 5 percentage points or
more per year), the plateau phase distinguished by high rates of use in each
year (perhaps varying by no more than 2 percentage points from year to
year), and the decline phase distinguished by steady decreases in youthful
marijuana use comparable in size to the increases observed during the
expansion phase. The rate of increase and subsequent decrease would
depend on the speed at which marijuana use spread within the target
population represented by each survey sample.

The findings from the NHSDA and MTF surveys in exhibit 1 fit this
overall pattern quite well, although the rate of increase during the apparent
expansion phase was modest. Nationwide, overall marijuana use had
steadily declined from 13 percent in 1979 to a low of 4 percent in 1992.
Marijuana use among high school seniors declined from a peak of 37
percent in 1978 to a low of 12 percent in 1992 (an average decline of 1.8
percentage points per year). NHSDA recorded a remarkably similar
decline in use among youthful household members (ages 18-20) for this
period. Then from 1992 to 1996, the rate among high school seniors
steadily increased to 22 percent (an average increase of 2.5 percentage
points per year); the rate among youthful household members rose more
modestly to 17 percent. Relatively stable rates were subsequently recorded
through 1999 for high school seniors and through 1998 for household
members, which suggests that the epidemic in the general population may
have reached a plateau around 1996.

The trend data on individual ADAM locations were often somewhat
ambiguous. The increases in youthful marijuana use detected during the
expansion phase were sometimes unsteady and the year-to-year variations
during the plateau phase were sometimes greater than 5 percentage points.
There are numerous possible reasons for year-to-year variations, including
changes in policing priorities and random chance (samples for individual
ADAM locations are much smaller than MTF and NHSDA samples).
Sometimes this variation confounded the study's efforts to precisely
pinpoint the timing of the phases of the New Marijuana Epidemic. In
response, small variations from one year to the next were often
disregarded by the authors as potentially attributable to the limited
precision of the ADAM estimates. Such ambiguous trends are clearly
identified in this report and the basis for an interpretation is provided. The
most credence was placed on strong trends consistently affecting
marijuana use across multiple years.

Exhibit 2 depicts the status in 1999 of the New Marijuana Epidemic at
each ADAM location across the Nation. By 1999, the marijuana epidemic
among arrestees had clearly reached the plateau phase at ADAM locations
in the Northeast, Midwest, and Southwest. Miami and San Diego did not
appear to have observed epidemics. The epidemic had shown signs of
possibly having plateaued at almost all of the other Southeast and West
Coast ADAM locations. The similarity in findings across ADAM
locations suggests that the New Marijuana Epidemic was national in
scope. Based on this finding, an ADAM program average was calculated
to facilitate presentation of the general characteristics of the phenomenon
by simply averaging findings across locations. This program average does
not necessarily represent the average across arrestees nationwide.
Furthermore, it is not necessarily a good idea to focus on this type of an
average when determining the rate of detected use of such other drugs as
cocaine/crack, amphetamines, and heroin because prevalence rates vary
more widely across locations. Indeed, even marijuana use was affected by
important local differences, which are depicted in exhibit 2.

Exhibit 3 shows that, on average, the variation in recent marijuana use 
detected among youthful ADAM arrestees conformed to the conceptual
model for the New Marijuana Epidemic and that year-to-year distortions
of the overall pattern were quite modest. From 1988 to 1990, detected
marijuana use among all adult arrestees declined, on average, from 35
percent to 19 percent and declined among youthful adult arrestees from 44
percent to 24 percent. Subsequently, the rate among youthful adult
arrestees increased steadily from 25 percent in 1991 to 57 percent in 1996
(an average of 6.4 percentage points per year), suggesting that the
expansion phase, on average, occurred among arrestees from 1991 to
1996.

This doubling of marijuana use among youthful ADAM arrestees provides
some of the strongest evidence to suggest that a New Marijuana Epidemic
has occurred, primarily among youths and especially among youths who
tend to get in trouble with the law. This increase preceded the ADAM
program's 1996 change in the standard for determining marijuana use and,
therefore, could not have been caused by that methodological
improvement. From 1996 to 1999, the rate of use among youthful adult
arrestees held steady at around 60 percent and the rate among all adult
arrestees held constant at around 37 percent. The modest increase of use
among youthful adult arrestees to 62 percent in 1999 may have resulted
from changes in the ADAM sampling procedure. Thus, the plateau phase
among arrestees appears to have set in by 1996 and lasted, on average, at
least through 1999.

All three major national surveys (NHSDA, MTF, and ADAM) recorded a
similar overall pattern in youthful marijuana use: a decline in the 1980s
reaching a low in the early 1990s, followed by a rise in the mid-1990s and
stabilization in the late 1990s. These findings, along with the ethnographic
information cited previously, strongly suggest that a new nationwide
epidemic in marijuana use passed through its expansion phase by 1996 and
was in its plateau phase through 1999.

There were several important differences across surveys. The increase in
marijuana use started among youthful adult arrestees (ADAM) about 1
year before it started within the general population (NHSDA and MTF). In
addition, the peak rate of reported past-month use among high school
seniors occurring during the plateau phase (about 22 percent) was far
below the previous peak (37 percent) recorded in the late 1970s. It was
also far below the peak rate of detected marijuana use among youthful
adult arrestees in the same period (about 57 percent) as well as their rate of
reported past-month use (about 60 percent).[13] This suggests that the
New Marijuana Epidemic started among those individuals who tended to
get in trouble with the law and spread more widely within this group than
among youths in the general population. Conceivably, the prevalence of
marijuana use in the general population could undergo another expansion
if use diffused to other youthful subpopulations. Further research is clearly
needed to identify which groups of mainstream youth have been most
affected so far.

The following sections examine geographic variation among ADAM
arrestees across the program's locations in the following regions:
Northeast, Midwest, Southeast, Southwest, and West Coast. From 1996 to
1999, the majority of ADAM locations detected rates of marijuana use
among adult and youthful adult arrestees close to the ADAM program
average shown in exhibit 3. However, five Midwest locations (Chicago,
Detroit, Indianapolis, Omaha, and St. Louis) had substantially higher rates,
while five Southwest and West Coast locations (Houston, Los Angeles,
Phoenix, San Antonio, and San Jose) had substantially lower rates.

The New Marijuana Epidemic among ADAM arrestees in the Northeast

Manhattan--plateau since 1996. Marijuana use in Manhattan had dropped
from 27 percent overall (i.e., among all adult arrestees) in 1987 to 16
percent in 1991. From 1991 to 1993, the popularity of marijuana started to
rise among youthful adult arrestees (hereinafter referred to as "youthful
arrestees"). Assessing the start date of the increase in the rate of use is
difficult because the upward trend was quite slow at first and a 1-year dip
in youthful marijuana use occurred in 1993. Subsequently, the popularity
of marijuana among youthful arrestees increased to a peak of 61 percent in
1996. From 1996 to 1999, the rate of marijuana use among youthful
arrestees held steady at about 60 percent, with the overall rate holding at
about 30 percent.

Philadelphia--plateau since 1995. Marijuana use among all adult arrestees
in Philadelphia dropped precipitously from 30 percent in 1988 to 16
percent in 1990. From 1990 to 1993, marijuana use among youthful
arrestees expanded rapidly and the rate among all adult arrestees returned
to its former level. In 1993, the rate among youthful arrestees appeared to
have entered a plateau at about 52 percent, but it subsequently inched up to
59 percent in 1995. The rate among youthful arrestees remained around 60
percent from 1995 through 1999, and the overall rate held steady around
35 percent.

Washington, D.C.--plateau since 1996. In 1990, only 7 percent of all
Washington, D.C., adult arrestees were detected as recent marijuana users.
The rate increased rapidly among youthful arrestees and then among older
arrestees. By 1996, about 60 percent of youthful arrestees and 35 percent
of all arrestees were detected as recent marijuana users. These rates
remained relatively stable from 1996 through 1998. (This location did not
collect a full sample in 1999.)

The New Marijuana Epidemic among ADAM arrestees in the Midwest

Chicago--plateau since 1996. Marijuana use among all adult arrestees in
Chicago dropped from 48 percent in 1988 to 23 percent in 1991. In 1993,
however, the overall rate bounced up to about 40 percent, where it
approximately remained through 1999. The rate of recent marijuana use
detected among youthful arrestees rose dramatically from 27 percent in
1992 to 75 percent in 1996, where it approximately remained through
1999.

Cleveland--plateau since 1998. Marijuana use among all adult arrestees in
Cleveland dropped from 26 percent in 1988 to 11 percent in 1991.
Subsequently, the rate among youthful arrestees began a steady rise from
14 percent in 1991 to 72 percent by 1998. The overall rate reached just
below 40 percent in 1997, where it remained through 1999. The rate of
marijuana use detected among youthful arrestees in 1999 dipped slightly,
suggesting that the epidemic in Cleveland had entered a plateau in 1998.

Detroit--plateau since 1995. Marijuana use among all adult arrestees in
Detroit dropped from 32 percent in 1988 to 13 percent by 1990.
Subsequently, the rate among youthful arrestees increased steadily from 25
percent in 1990 to 73 percent in 1995. The rate of marijuana use detected
among youthful arrestees fluctuated in a broad range from 62 percent to 75
percent from 1995 through 1999. The rate of recent marijuana use detected
among all adult arrestees inched upward from 38 percent in 1995 to 46
percent in 1999.

Indianapolis--plateau since 1996. Marijuana use among all adult arrestees
in Indianapolis dropped steadily from 41 percent in 1988 to 23 percent in
1991. Subsequently, the rate among youthful arrestees increased steadily
from a low of 27 percent in 1991 to 70 percent in 1996 and remained
around that level through 1999. Overall, the rate of recent marijuana use
ranged from 39 to 45 percent from 1995 through 1999.

Omaha--plateau since 1996. Marijuana use among all adult arrestees in
Omaha dropped from 45 per-cent in 1988 to 21 percent in 1990.
Subsequently, that rate rose steadily to 39 percent in 1992 and to 49
percent by 1996. The rate among youthful arrestees rose from 25 percent
in 1990 and then held steady around 55 percent from 1993 through 1995.
In 1996, the rate of marijuana use detected among youthful arrestees
jumped to 71 percent, where it approximately remained through 1999.
This change was probably not attributable to a change in the ADAM cutoff
standard for determining recent marijuana use. (The prevalence of
marijuana use among Omaha's youthful arrestees in 1995 increased only
slightly from 53 percent under the previous 100 nanogram cutoff to 56
percent under the new 50 nanogram standard.)

St. Louis--plateau since 1996. Marijuana use among youthful arrestees in
St. Louis rose steadily from a low of 15 percent in 1990 to 72 percent in
1996, where it approximately remained through 1998. The rate of overall
use increased from a low of 14 percent in 1991 to a steady 45 percent by
1996, where it remained through 1998. (This ADAM location did not
collect a sample in 1999.)

The New Marijuana Epidemic among ADAM arrestees in the Southeast

Atlanta--plateau/possibly expansion. In 1990, the prevalence of recent
marijuana use detected among youthful (6 percent) and all adult (3
percent) arrestees in Atlanta was the lowest of any ADAM location. The
rate among all adult arrestees increased to 33 percent by 1996. The
epidemic did not appear centered on youthful arrestees only; rather, the
rate of recent marijuana use detected increased among all adult arrestees as
early as 1991. The rate among youthful arrestees, however, did increase
the most, reaching 69 percent in 1996. From 1996 to 1998, the rate among
youthful arrestees drifted slightly downward to 62 percent. The rate of use
among all adult arrestees also decreased, from 33 percent in 1997 to 25
percent in 1998. Both rates bounced back to new peaks in 1999,
suggesting the New Marijuana Epidemic in Atlanta could still have been
in its expansion phase. On the other hand, the relatively steady rate
observed from 1996 to 1998 suggests that the epidemic might have
plateaued by 1996 and that the 1999 jump was an anomalous fluctuation.

Birmingham--plateau/possible expansion. Marijuana use among all adult
arrestees in Birmingham dropped precipitously from 33 percent in 1988 to
12 percent by 1990. Subsequently, the rate among youthful arrestees
increased dramatically from 15 percent in 1990 to 64 percent in 1996. The
overall rate reached 40 percent in 1996. In 1998, the rate among youthful
arrestees declined modestly to 57 percent and then jumped to 69 percent in
1999. This suggests that the expansion phase may have continued through
1999. On the other hand, the lack of any increase in the rate of use from
1996 to 1998 suggests that the epidemic may have plateaued by 1996 and
that the 1999 jump was an anomalous fluctuation.

Fort Lauderdale--plateau/possible expansion. Marijuana use among all
adult arrestees in Fort Lauderdale dropped from 42 percent in 1988 to 20
percent in 1990. The rate of detected marijuana use among youthful
arrestees started a very slow but steady increase from a low of 28 percent
in 1990 to 63 percent in 1998. The overall rate increased even more
slowly, from 20 percent in 1990 to 38 percent in 1998. The modest dip in
the rate in 1999 suggests that the epidemic might have reached a plateau in
1998. On the other hand, the relatively slow expansion and a history of 2
previous years in which the expansion appeared to have halted (1992-93
and 1996-97) suggest that the expansion may not have plateaued by 1999.

Miami--no epidemic. From 1988 through 1999, marijuana use among all
adult arrestees in Miami fluctuated around 30 percent. The rate among
youthful arrestees fluctuated within a wider range--between 31 and 66
percent. The dramatic 1-year jump in marijuana use among youthful
arrestees, from 45 percent in 1998 to 66 percent in 1999, may have been
caused by changes to the ADAM sampling procedures. The data suggest
no sustained trend in marijuana use has occurred among arrestees. Miami
experienced neither a sustained decline in marijuana use among arrestees
nor the epidemic-like growth in use among youthful arrestees observed at
other ADAM locations.

The New Marijuana Epidemic among ADAM arrestees in the Southwest

Dallas--plateau since 1996. Marijuana use among all adult arrestees in
Dallas had dropped steadily from 32 percent in 1988 to 17 percent in
1991. The rate of detected marijuana use among youthful arrestees
subsequently increased from 22 percent in 1991 to 57 percent in 1996. The
overall rate increased to 38 percent. Both rates remained stable from 1996
through 1999.

Denver--plateau since 1994. In Denver, the rate of detected marijuana use
among youthful arrestees rose rapidly from 26 percent in 1991 to 60
percent in 1994, dropped modestly to 54 percent in 1995, and inched up to
62 percent by 1999. The overall rate rose more slowly, from 23 percent in
1991 to 41 percent by 1999.

Houston--plateau since 1995. The rate of detected marijuana use among all
adult arrestees in Houston dropped precipitously from 43 percent in 1988
to 14 percent by 1991. The rate among youthful arrestees bounced back
from a low of 19 percent in 1992 to 43 percent in 1995. In 1996 and 1997,
the rate among youthful arrestees dipped to about 31 percent and then
returned to 49 percent by 1999. This increase in marijuana use among
youthful arrestees--well above the previously established plateau level in
1995--may have been attributable to changes in ADAM sampling
procedures. By 1999, the rate of detected marijuana use overall had
returned to 31 percent, still far below the rate observed in the late 1980s
and below the ADAM program average.

New Orleans--plateau since 1995. Marijuana use among all adult arrestees
in New Orleans dropped precipitously from 46 percent in 1987 to 14
percent by 1991. Marijuana use among youthful arrestees subsequently
increased from 17 percent (1991) to 54 percent (1995) and then fluctuated
in the 50 percent to 60 percent range. The overall rate of detected
marijuana use inched up to 35 percent by 1999, still well below the rate
observed in the late 1980s.

Phoenix--plateau since 1998. The rate of detected marijuana use among all
adult arrestees in Phoenix dropped steadily from 42 percent in 1987 to 19
percent in 1991. Subsequently, the rate among youthful arrestees entered a
slow but steady expansion, increasing from 22 percent in 1991 to 40
percent in 1995. At that time, the marijuana epidemic appeared to have
entered a plateau. However, youthful marijuana use jumped to 54 percent
in 1998, where it remained in 1999. This increase suggests that the
marijuana epidemic may have diffused in the 1997-98 period to another
portion of youths who tend to get arrested. This change could have also
been caused by changes in police priorities or ADAM sampling
procedures.

San Antonio--plateau since 1996. Marijuana use among all adult arrestees
in San Antonio decreased from 34 percent in 1988 to 18 percent by 1991.
The rate among youthful arrestees then slowly increased from 20 percent
in 1991 to 45 percent in 1996, where it remained through 1999. Overall
marijuana use had increased to 32 percent by 1996 and fluctuated around
this rate through 1999.

The New Marijuana Epidemic among ADAM arrestees on the West Coast

Los Angeles--plateau/possible expansion. It is difficult to determine the
timing of a New Marijuana Epidemic in Los Angeles because the rate of
increase in detected marijuana use among youthful arrestees was very slow
in the early 1990s and because it took a dip in 1994, which suggests the
rate had plateaued. However, the increase in detected marijuana use
among youthful arrestees from 22 percent in 1991 to 49 percent in 1996
strongly suggests that a marijuana epidemic took place. In 1997, the rate
among youthful arrestees declined modestly to 46 percent and inched up to
54 percent by 1999. This continued increase suggests that the epidemic
may not yet have plateaued by 1999. However, it is possible that the
modest increase in youthful marijuana use from 49 percent (1998) to 54
percent (1999) was caused by changes in ADAM sampling procedures. If
this was the case, the marijuana epidemic among youthful arrestees in Los
Angeles may have plateaued as early as 1996. The overall rate of
marijuana use inched up from 16 percent in 1991 to a high of 30 percent in
1999.

Portland (Oregon)--expansion 1992-99. Marijuana use among all adult
arrestees in Portland decreased from 47 percent in 1988 to 25 percent in
1992. The rate of detected marijuana use among youthful arrestees
subsequently expanded from 28 percent in 1992 to 57 percent in 1999. The
overall rate increased only modestly to a peak of 33 percent in 1998.

San Diego--no epidemic. Marijuana use among San Diego's youthful
arrestees remained steady and relatively high from 1987 through 1999,
ranging from 37 to 55 percent. Marijuana use among all adult arrestees
exhibited a modest drop from 44 percent in 1988 to 29 percent in 1991.
The rate then fluctuated around 34 percent through 1999. The rate of
detected marijuana use among youthful arrestees exhibited a modest
1-year increase from 37 percent in 1991 to 47 percent in 1992. The rate
among youthful arrestees subsequently fluctuated in the mid-40-percent
range. The modest dip and recovery in youthful marijuana use from 1989
to 1992 seem much too small to constitute a new drug epidemic, although
their timing is consistent with that of the New Marijuana Epidemic at
other ADAM locations. Another steady but short increase in youthful
marijuana use occurred from 1997 to 1999, when the rate among youthful
arrestees inched up from 44 to 55 percent. Again, the short period and
rather modest increase suggest that this change was not part of a longer,
sustained epidemic.

San Jose--plateau since 1995. Overall, marijuana use among San Jose
arrestees was relatively stable at about 24 percent from 1989 through
1998. The rate among youthful arrestees increased from 21 percent in
1992 to 43 percent in 1995, where it roughly remained through 1998. The
sharp increase to 56 percent in 1999 may be an anomalous 1-year
fluctuation.

Conclusion

This study identified that the increase in marijuana use among ADAM
arrestees in the 1990s generally conformed to the conceptual model
described earlier for the diffusion of a drug epidemic. Marijuana appears
to have become the drug of choice among youths coming of age in the
1990s who tend to get in trouble with the law in the same way that crack
had been the drug of choice previously. Analyses with two additional
datasets of general population samples (the NHSDA and MTF surveys)
further confirmed the existence and timing of this New Marijuana
Epidemic. Continued monitoring of drug use among arrestees is essential
to determine how long prevailing conditions will persist. Some of the key
issues include the following:

 o How long will marijuana remain the drug of choice among youths
coming of age who tend to get in trouble with the law?

 o Will marijuana-using members of the New Marijuana Generation
continue to avoid use of other illicit drugs?

 o To what extent will marijuana-using members of the New Marijuana
Generation desist from such use as they grow older?

There are numerous ways to attempt to control drug abuse, including
prevention, treatment, interdiction, and law enforcement. In response to
recent trends, drug abuse control policies might logically shift much of
their focus to marijuana. However, this is not as simple as just targeting
marijuana use and users instead of crack or heroin users. For one, the
nature of marijuana abuse is quite different, as noted by Grinspoon and
Bakalar, who report that proportionately fewer marijuana smokers become
dependent than users of alcohol, tobacco, heroin, or cocaine.[14] They
suggest that psychotherapy may be the most appropriate treatment for a
troubled youth who uses marijuana frequently, such as one who manifests
alienation, emotional withdrawal, overreaction to minor frustration, and
antisocial behavior. They emphasize that the treatment is not for marijuana
use itself but for an underlying problem that has marijuana abuse as one of
its symptoms. They also suggest that the health risks of marijuana use are
much less profound than those of cocaine or heroin use.

A standing argument for controlling marijuana use, based on the gateway
theory, is that it can lead to use of more dangerous drugs. As determined
in this study, however, the drug of choice for persons born in the 1970s
and coming of age in the 1990s has been marijuana. These youths have
been much less prone to progress to other drugs than their predecessors.
This suggests that the gateway theory may be less relevant to their
substance use experiences, which would be good news. It would also be
good news if the marijuana use were associated with a rejection of crack
and heroin due to their potentially devastating consequences.[15]

This rejection of other drugs may not be as characteristic of the broader
population. From 1992 to 1997, the proportion of high school seniors
reporting lifetime use of LSD increased from 8.6 percent to 13.6 percent,
its highest recorded level since the start of the MTF program in 1975.[16]
Use of hallucinogens in England and the United States has been frequently
associated with the rave or dance party scene, typically involving white
youths from middle- and upper-class suburban enclaves.[17] However,
that is a different story about a different population of youths.

It would appear that more has changed than the prevailing drug of choice
among arrestees. Ethnographic studies in inner-city communities suggest
that there has been a dramatic shift in the subculture of drug use and that
interpersonal interactions have become more congenial and less
violent.[18] In this way, drug-using members of the New Marijuana
Generation are damaging themselves less physically and socially than the
preceding generations of crack smokers and heroin injectors. They are also
causing much less harm to the broader population.

In this regard, the potential for integrating persons from distressed
inner-city communities into mainstream culture seems more promising
than in the 1970s and 1980s. Perhaps this is the time to deemphasize
"tough" drug enforcement policies in favor of indirect drug abuse control
through the reduction of the economic, educational, and social barriers
faced by many inner-city youths in establishing a healthy and productive
mainstream lifestyle. Providing youths struggling in distressed inner-city
households with a greater stake in society may help create a more
productive labor force and ensure further declines in drug abuse and its
attendant criminality. If inner-city youths born in the 1970s who get in
trouble with the law could be transformed into fully employable workers,
their marijuana use might also decline as they assume conventional adult
roles, just as marijuana use tends to recede among members of the general
population.[19]

Notes

1. Office of National Drug Control Policy, The National Drug Control
Strategy: 1997, Washington, DC: Office of National Drug Control Policy,
1997:23, NCJ 163915.

2. Gfroerer, Joseph C., and Joan F. Epstein, "Marijuana Initiates and Their
Impact on Future Drug Abuse Treatment Need," Drug and Alcohol
Dependence 54(3)(1999):229-237.

3. Research in a wide variety of fields has documented that new
innovations often spread within a population following a pattern similar to
a disease epidemic (see Rogers, Everett M., Diffusion of Innovations, 4th
ed., New York: Free Press, 1995). The term "epidemic" is employed in
this report as a synonym for "diffusion of innovation" and refers to the
rapid and broad spreading of a practice (such as smoking marijuana)
within a population or subpopulation (such as among 16- to 25-year-olds).

4. Golub, Andrew, and Bruce D. Johnson, "A Recent Decline in Cocaine
Use Among Youthful Arrestees in Manhattan (1987-1993)," American
Journal of Public Health 84(8)(1994):1250-1254; Golub, Andrew, and
Bruce D. Johnson, Crack's Decline: Some Surprises Across U.S. Cities,
Research in Brief, Washington, DC: U.S. Department of Justice, National
Institute of Justice, July 1997, NCJ 165707.

5. Golub, Andrew, and Bruce D. Johnson, "Cohort Changes in Illegal
Drug Use Among Arrestees in Manhattan: From the Heroin Injection
Generation to the Blunts Generation," Substance Use and Misuse
34(13)(1999):1733-1763; Johnson, Bruce D., and Andrew Golub,
"Generational Trends in Heroin Use and Injection Among Arrestees in
New York City," in One Hundred Years of Heroin, ed. David Musto,
Westport, CT: Greenwood, forthcoming.

6. In a more detailed report, the authors provide analyses of marijuana use
trends over time within five mutually exclusive age categories. See Golub,
Andrew, and Bruce D. Johnson, "Monitoring the Marijuana Upsurge With
DUF/ADAM Arrestees," final report submitted to the U.S. Department of
Justice, National Institute of Justice, Washington, DC, 2000.

7. Johnson, Bruce D., and Andrew Golub, "Generational Trends in Heroin
Use and Injection Among Arrestees in New York City."

8. Johnson, Bruce D., Andrew Golub, and Jeffrey Fagan, "Careers in
Crack, Drug Use, Drug Distribution and Nondrug Criminality," Crime and
Delinquency 41(3)(1995):275-295; Hamid, Ansley, "The Developmental
Cycle of a Drug Epidemic: The Cocaine Smoking Epidemic of
1981-1991," Journal of Psychoactive Drugs 24(1992):337-348.

9. Johnston, Lloyd D., Patrick M. O'Malley, and Jerald G. Bachman,
National Survey Results on Drug Use from the Monitoring the Future
Study, 1975-1998, vol. 1, Bethesda, MD: National Institutes of Health,
National Institute on Drug Abuse, 1999, NIH Publication No. 99-4660;
Substance Abuse and Mental Health Services Administration, National
Household Survey on Drug Abuse Series: H-10. Summary of Findings
from the 1998 National Household Survey on Drug Abuse, Rockville,
MD: Office of Applied Studies, 1999, Department of Health and Human
Services Publication No. (SMA) 99-3295.

10. Furst, R. Terry, Bruce D. Johnson, Eloise Dunlap, and Richard Curtis,
"The Stigmatized Image of the 'Crack Head': A Sociocultural Exploration
of a Barrier to Cocaine Smoking Among a Cohort of Youth in New York
City," Deviant Behavior 20(2)(1999):153-181; Golub, Andrew, and Bruce
D. Johnson, "Cohort Changes in Illegal Drug Use Among Arrestees in
Manhattan: From the Heroin Injection Generation to the Blunts
Generation," Substance Use and Misuse 34(13)(1999):1733-1763;
Sifaneck, Stephen J., and C. Small, "Blunts and Forties: The Drugs of
Choice for the New Generation," New York: National Development and
Research Institutes, Inc., 1997, working manuscript; Sifaneck, Stephen J.,
and Charles D. Kaplan, "New Rituals of Cannabis Preparation and
Self-Regulation in Two Cultural Settings and Their Implications for
Secondary Prevention," New York: National Development and Research
Institutes, Inc., 1996, working manuscript.

11. Department of Health and Human Services, Youth Use of Cigars:
Patterns of Use and Perceptions of Risk, Washington, DC: Department of
Health and Human Services, 1999, publication number OEI-06098-00030.

12. Community Epidemiology Work Group, Identifying and Monitoring
Emerging Drug Use Problems: A Retrospective Analysis of Drug Abuse
Data/Information, Bethesda, MD: National Institute on Drug Abuse, 1999.
Available online at www.nida.nih.gov/cweg/retro.html.

13. The rate of self-reported past-month use among youthful adult
arrestees was calculated separately to support this comparison. Across all
sites and interview years, most youthful adult arrestees (80 percent)
detected as recent marijuana users via urinalysis also reported past-month
use. The nondisclosers were more than offset by individuals who tested
negative for recent marijuana use but still reported use in the past month.

14. Grinspoon, Lester, and James B. Bakalar, "Marijuana," in Substance
Abuse: A Comprehensive Textbook, ed. J.H. Lowinson, P. Ruiz, R.B.
Millman, and J.G. Langrod, 3d ed., Baltimore: Williams and Wilkins,
1997:199-206.

15. Furst, R. Terry, Bruce D. Johnson, Eloise Dunlap, and Richard Curtis,
"The Stigmatized Image of the 'Crack Head': A Sociocultural Exploration
of a Barrier to Cocaine Smoking Among a Cohort of Youth in New York
City"; Golub, Andrew, and Bruce D. Johnson, "Cohort Changes in Illegal
Drug Use Among Arrestees in Manhattan: From the Heroin Injection
Generation to the Blunts Generation."

16. Johnston, Lloyd D., Patrick M. O'Malley, and Jerald G. Bachman,
National Survey Results on Drug Use from the Monitoring the Future
Study, 1975-1998.

17. Parker, Howard, Judith Aldridge, and Fiona Measham, Illegal Leisure:
The Normalization of Adolescent Recreational Drug Use (Adolescence
and Society), London: Routledge, 1998; Hunt, Dana, Rise of Hallucinogen
Use, Research in Brief, Washington, DC: U.S. Department of Justice,
National Institute of Justice, 1997, NCJ 166607.

18. Johnson, Bruce D., Andrew Golub, and Eloise Dunlap, "The Rise and
Decline of Hard Drugs, Drug Markets, and Violence in New York City,"
in The Crime Drop in America, ed. Alfred Blumstein and Joel Wallman,
New York: Cambridge, 2000:164-206.

19. Bachman, Jerald G., Katherine N. Wadsworth, Patrick M. O'Malley,
Lloyd D. Johnston, and John E. Schulenberg, Smoking, Drinking, and
Drug Use in Young Adulthood: The Impacts of New Freedoms and New
Responsibilities, Mahwah, NJ: Erlbaum, 1997.

---------------------------

Issues and Findings

Discussed in this Brief: Trends in marijuana use detected through
urinalysis among booked adult arrestees at 23 locations across the Nation
served by the Arrestee Drug Abuse Monitoring (ADAM) program from
1987 through 1999 as well as trends within the mainstream population
based on self-reports of past-month marijuana use recorded by the
National Household Survey on Drug Abuse (NHSDA) and Monitoring the
Future (MTF) programs.

Key issues: An epidemiological perspective is taken to place in context the
increased use of marijuana among arrestees and the general population.
The course of the recent marijuana upsurge is compared with that
observed for previous crack and heroin epidemics in which four phases
with distinct variations in prevalence and age of users occurred. The
analysis also compares time trends in marijuana use across age groups,
populations, and geographic locations.

Key findings:

 o Increases in marijuana use during the study period were limited
primarily to youths. Starting around 1991, most ADAM locations
experienced a rapid increase in recent use among youthful adult arrestees
(ages 18-20), from an average low of 25 percent in 1991 to 57 percent in
1996, as detected by urinalysis. The MTF and NHSDA surveys also
recorded rapid but more modest increases in youthful marijuana use within
the mainstream population starting in 1992 (1 year later than among
ADAM arrestees). Around 1996, the rates of marijuana use among arrestee
and mainstream populations reached a plateau.

 o With exceptions at a few ADAM locations, the pattern of growth in
marijuana use among youthful adult arrestees was similar to that observed
previously for heroin and crack: lull, rapid expansion, and plateau. Use of
both heroin and crack is now in decline.

 o Marijuana appears to be the drug of choice for arrestees born since
1970, who seem much less likely to progress to crack or heroin injection
than their predecessors.

Target audience: Local law enforcement and public health officials,
drug-crime researchers, administrators of juvenile justice agencies and
youth departments, and local criminal justice policymakers.

---------------------------

The Gateway Theory

Much research has identified that most American youths tend to progress
through as many as four stages of substance use: nonuse, alcohol/tobacco,
marijuana, and other drugs including cocaine and heroin.[a] Individuals
who do not use substances associated with one stage rarely use those
associated with later stages, but not all users at one stage progress to the
next.[b] Because of their intermediary role, alcohol, tobacco, and
marijuana have come to be regarded as "gateway drugs." Today, policies
pertaining to substance use prevention seek to forestall or delay youthful
use of gateway drugs to reduce the likelihood of subsequent abuse of drugs
like heroin and crack.

In contrast, several analyses suggest the gateway sequence may not be as
relevant to the inner-city populations that disproportionately generate
youths who get in trouble with both drug abuse and the law.[c] Moreover,
the gateway sequence may no longer characterize the experiences of
mainstream youths. Calculations based on National Household Survey on
Drug Abuse data suggest that youths coming of age in the 1990s were
much less likely to progress from marijuana to cocaine powder, crack, or
heroin than were youths born previously.[d] 

These recent studies suggest that youthful substance use progression
reflects cultural or subcultural norms among youths about which
substances are acceptable and that these norms vary over time and across
locations. Thus, it seems essential to monitor not just which substances
youths are using but what that substance use represents to them.

a. Kandel, Denise B., "Stages in Adolescent Involvement in Drug Use,"
Science 190(1975): 912-914.

b. Ibid. For a review of replications, see Kandel, Denise B., ed., Stages and
Pathways of Involvement in Drug Use: Examining the Gateway
Hypothesis, New York: Cambridge, forthcoming.

c. Golub, Andrew, and Bruce D. Johnson, "Substance Use Progression and
Hard Drug Abuse in Inner-City New York," in Stages and Pathways of
Involvement in Drug Use: Examining the Gateway Hypothesis, ed. Denise
B. Kandel, New York: Cambridge, forthcoming.

d. Golub, Andrew, and Bruce D. Johnson, "Variation in Youthful Risk of
Progression From Alcohol and Tobacco to Marijuana and Hard Drugs
Across Generations," American Journal of Public Health
91(2)(2001):225-232.

---------------------------

The Study's Data Sources

The authors collected data from three major programs: Arrestee Drug
Abuse Monitoring (ADAM), National Household Survey on Drug Abuse
(NHSDA), and Monitoring the Future (MTF). The absolute magnitude in
the prevalence of recent marijuana use was expected to differ among the
foregoing data sources because of differences in sample populations
(across ADAM locations and across NHSDA and MTF surveys),
differences in survey procedures, and the use of urine tests for ADAM in
contrast to self-reports for NHSDA and MTF.

Arrestee Drug Abuse Monitoring program. In 1987, the National Institute
of Justice (NIJ) established the Drug Use Forecasting (DUF) program to
measure trends in illicit drug use among booked arrestees in most large
cities (or counties) with a total population of at least 1 million, as well as
in many smaller cities for geographical diversity. In 1997, DUF evolved
into the ADAM program, which plans to expand to 75 locations over the
next few years.[a] The program collects urine samples (along with
self-reported information) from about 300 adult arrestees each quarter at
each location. Female arrestees are oversampled at many locations and
constitute about 30 percent of the total. Some locations also recruit
samples of juvenile arrestees. This study examined trends at the 23
locations using information obtained from more than 300,000 arrestees
between 1987 and 1999. ADAM samples typically are not representative
of the general population in communities where data collection occurs.
Given the drug-crime nexus, ADAM data provide excellent information
about drug use among many of the most serious drug abusers at each
location. This information is of particular interest to criminal justice and
other agencies. Analyses of ADAM data may be of even broader interest
to the extent that drug use among arrestees tends to parallel or perhaps
even lead trends in the general population.

At inception, the DUF program sought to monitor substance use among
serious offenders: individuals charged with a felony offense were
oversampled; individuals charged with a citation offense were excluded
from DUF samples at most locations; and individuals charged with drug
offenses were not allowed to exceed 20 percent of the sample.[b] As part
of the transition to ADAM, NIJ phased in sampling strategies so that
ADAM samples would be representative of arrestees passing through the
central booking facility at each location. Starting in 1998, the prevalence
of arrestees for drug offenses and citations increased substantially. Several
locations experienced increases in detected marijuana use in 1999
inconsistent with the trend in previous years, including, most notably,
Atlanta, Birmingham, Houston, Miami, Phoenix, San Diego, and San Jose.
Continuation of the upward trend in Los Angeles and Portland also may
have been due to the change in sampling strategy.

Throughout the life of the DUF and ADAM programs, urine testing and
many core questions have remained constant, allowing for analysis of
trends over time. Urine test results provide particularly valid indications of
recent marijuana use. Marijuana metabolites tend to remain in the body.
Marijuana consumption can be detected by the EMIT (Enzyme Multiplied
Immunoassay Testing) urinalysis screen used by ADAM up to 7 days after
last use for infrequent users and 30 days or longer for chronic users. In
contrast, the drug detection period for opiates (such as heroin) and cocaine
is only 2 to 3 days. In 1996, the cutoff level for determining recent
marijuana use was lowered from 100 to 50 nanograms.[c] More than
34,000 samples from 1995 were tested at both cutoff levels. Overall, the
prevalence of detected marijuana use increased 5 to 7 percentage points
when the lower cutoff level was used. The difference was most
pronounced among very young arrestees (under age 15) and older arrestees
(over age 30), two groups that tend to use marijuana less frequently.

National Household Survey on Drug Abuse program. NHSDA was
established in 1971 to measure the prevalence and correlates of illegal
drug use and monitor trends over time in the noninstitutionalized
population of the United States.[d] The survey tends to undersample many
of the most serious drug abusers, who are prone to incarceration, residence
in other institutions, and unstable living arrangements. Eligible
participants are visited and interviewed in their homes. Through 1998,
respondents were given a separate sheet to record their confidential
answers to questions about drug use to help ensure disclosure of sensitive
information. The survey was conducted in 1971 and 1972 and then every 2
or 3 years until 1990, when it became an annual survey. Analyses
presented in this report are based on more than 200,000 responses
available in public use data files for surveys conducted in 1979, 1982,
1985, 1988, and 1990-97 and in a published report for 1998.[e] NHSDA
employs a complex sampling design and oversamples Hispanics, blacks,
and youths ages 12 to 17. The authors used sample weights in all
calculations to obtain unbiased estimates.

Monitoring the Future program. Each spring since 1975, the University of
Michigan's Institute for Social Research has conducted a survey to
estimate the prevalence of drug use among high school seniors in the
United States and to monitor trends over time.[f] The survey tends to
undersample many of the most serious drug users, who are
disproportionately likely to drop out of school or be absent on the day of
the survey. Students at selected schools complete confidential
questionnaires at their own pace during a normal class period. Analyses
presented in this report are based on more than 350,000 responses obtained
in the 1976-97 period and contained in a published report for 1998-99.[g]
The MTF program employs a complex sampling design. The authors used
sample weights in all analyses to obtain unbiased estimates of substance
use.

a. National Institute of Justice, 1998 Annual Report on Drug Use Among
Adult and Juvenile Arrestees, Washington, DC: U.S. Department of
Justice, National Institute of Justice, 1999, NCJ 175656.

b. National Institute of Justice, 1999 Annual Report on Drug Use Among
Adult and Juvenile Arrestees, Washington, DC: U.S. Department of
Justice, National Institute of Justice, 2000, NCJ 181426.

c. National Institute of Justice, Drug Use Forecasting: Annual Report on
Adult and Juvenile Arrestees, 1996, Washington, DC: U.S. Department of
Justice, National Institute of Justice, 1997, NCJ 176800.

d. Substance Abuse and Mental Health Services Administration, National
Household Survey on Drug Abuse Series: H-10. Summary of Findings
from the 1998 National Household Survey on Drug Abuse, Rockville,
MD: Office of Applied Studies, 1999, U.S. Department of Health and
Human Services Publication No. (SMA) 99-3295.

e. Ibid.

f. Johnston, Lloyd D., Patrick M. O'Malley, and Jerald G. Bachman,
National Survey Results on Drug Use from the Monitoring the Future
Study, 1975-1998, vol. 1, Bethesda, MD: National Institutes of Health,
National Institute on Drug Abuse, 1999, NIH Publication No. 99-4660.

g. Johnston, Lloyd D., Patrick M. O'Malley, and Jerald G. Bachman, Drug
Trends in 1999 Are Mixed, press release, Ann Arbor, MI: University of
Michigan News and Information Services, 1999. Available online at
www.monitoringthefuture.org/pressreleases/99drugpr.html.

---------------------------

Distinguishing Age, Period, and Cohort Effects

Exhibit A shows the ADAM program average of detected marijuana use as
a function of both an arrestee's birth year and the year of the ADAM
interview. The exhibit distinguishes three types of social factors that can
influence an individual's drug use: age, period, and cohort effects.* Each
row traces the marijuana use history of persons born in a given year,
known as a birth cohort. The entries in each row reflect changes in a birth
cohort's level of marijuana use as arrestees age, to the extent that the
ADAM program recruits from roughly the same population in a similar
way each year. Age effects are those behaviors that develop as people
grow older. Among the youngest birth cohorts, the prevalence of
marijuana use typically increased in their late teens. For example, among
the 1977 birth cohort, the rate of detected marijuana use grew from 32
percent at age 16 (in 1993) to 55 percent at age 18 (in 1995). To facilitate
identification of age effects, the exhibit highlights three diagonals
associated with ages 30, 25, and 18, respectively.

The use of marijuana was affected by historical occurrences, or period
effects, as shown by decreased levels of use (1988-90) and increased
levels of use (1991-93) among persons from each birth cohort. Overall, as
recorded in the bottom row of the exhibit, marijuana use among all adult
arrestees (age 18+) declined from 35 percent in 1988 to 19 percent in 1990
and 1991. This broad decline could have been the result of increased drug
law enforcement; greater involvement with other drugs, such as crack; or
decreased availability of marijuana. The overall rate subsequently returned
to 28 percent by 1993. This 5-year dip in usage (1988-93) was reflected in
each birth cohort's marijuana use experiences. For example, the marijuana
use among arrestees born in 1960 declined from 39 percent (1988) to 17
percent (1990) and then returned to 24 percent (1993), where it remained
relatively steady through 1998. The nature of this dip suggests that for the
1960 birth cohort, the period effect had an immediate impact of reducing
marijuana use by 22 percentage points (from 39 to 17 percent) and a
somewhat smaller long-term effect of reducing marijuana use by 15
percentage points. The older birth cohorts experienced sharp short-term
declines and more modest long-term declines from 1988 to 1993, except
for the oldest arrestees. Arrestees born in the 1901-39 period had a
relatively low level of marijuana use of 9 percent in 1988, which declined
to 5 percent in 1990 but returned to a slightly higher level of 11 percent in
1993.

Some historical events permanently affect individuals at an impressionable
age. Many persons who came of age during the Heroin Injection and
Crack Epidemics persisted in their habits throughout much of their lives.
In this manner, the use of each drug became associated with members of a
particular birth cohort, a cohort effect. Marijuana use may have a similar
effect on this new generation of drug users. The 1972 birth cohort reached
age 18 in 1990, right at the lull in marijuana use among arrestees. Their
rate of marijuana use dropped from 30 percent at age 17 (in 1989) to 20
percent at age 18 (1990) but continually increased to 47 percent by 1996.
For this birth cohort, the period of lower marijuana use led them to
postpone, but did not forestall, their involvement with marijuana. Unlike
previous birth cohorts, which had established their peak level of marijuana
use by age 18, arrestees in the 1972-76 birth cohorts exhibited a rise in
marijuana use in their early twenties. It would appear that more and more
of them became involved with marijuana during the expansion phase of
the New Marijuana Epidemic.

By 1996, a solid plateau in marijuana use had been established.
Approximately 60 percent of arrestees who reached age 18 from 1996 to
1998 (the 1978-80 birth cohorts) were detected as marijuana users in 1996
and as they aged subsequently. From 1996 to 1998, the rate of marijuana
use within each birth cohort remained relatively constant or declined
modestly.

* Discerning age, period, and cohort effects is complicated by the
multicolinearity of these parameters-specifically, age = (interview year) -
(birth year). Hence, it is not possible to naively include all three factors as
independent variables in an algebraic equation such as employed in
regression analysis. However, all three types of effects result in a
distinctive pattern of birth cohort participation over time that can be
discerned in a two-way table such as the exhibit.

---------------------------

Three Generations of Drug Use Among Arrestees 

In a previous study,[a] the authors used ADAM data for Manhattan to
identify three generations of arrestees with distinct drug use patterns: the
Heroin Injection Generation (born 1945-54), Cocaine/Crack Generation
(born 1955-69), and Marijuana/Blunts Generation (born 1970 and later).
These findings show variation across birth cohorts in reported lifetime
(ever) heroin injection,[b] lifetime (ever) crack use, and detected
marijuana use.[c] The authors performed a comparable analysis for each
ADAM location and produced similar findings at each, with only two
exceptions.[d] In Phoenix, it appears that, among arrestees, the Crack
Epidemic had not ended by 1998. San Antonio appears to have never
experienced a serious epidemic of crack use.

Findings based on all available ADAM data from 1989 to 1998 in
Washington, D.C., were typical (see exhibit A). The prevalence of lifetime
heroin injection peaked with persons born around 1950 and exhibited a
sustained decline starting somewhere around the 1954 birth cohort,
reaching near zero among birth cohorts of the 1970s. The prevalence of
lifetime crack cocaine use peaked among persons born around 1960 and
started to decline around the 1964 birth cohort. Recent marijuana use
exhibited a dramatic and continuous increase with successive birth cohorts
starting around 1970. Arrestees born since 1970, but especially after 1974,
were likely to be detected as recent marijuana users and very unlikely to
report lifetime heroin injection or crack use.

a. Golub, Andrew, and Bruce D. Johnson, "Cohort Changes in Illegal Drug
Use Among Arrestees in Manhattan: From the Heroin Injection
Generation to the Blunts Generation," Substance Use and Misuse
34(13)(1999):1733-1763.

b. Lifetime heroin injection was approximately determined from persons
who reported both lifetime heroin use and lifetime injection of illicit
drugs. This calculation was necessary because the ADAM questionnaire
did not ask explicitly about heroin injection in all years of the survey. At
some locations, many individuals reported injection drug use but not
heroin use (they may have been injecting cocaine or amphetamines) and
others reported heroin use but no injection drug use (many were
presumably sniffers).

c. Variations in substance use across birth years can be caused by age,
period, or cohort effects. The authors confirmed that heroin injection,
crack smoking, and marijuana use among ADAM-Manhattan arrestees
were the result of period effects in three separate age-period-cohort
analyses for detected use of opiates, cocaine, and marijuana (see Golub,
Andrew, and Bruce D. Johnson, "Cohort Changes in Illegal Drug Use
Among Arrestees in Manhattan: From the Heroin Injection Generation to
the Blunts Generation," Substance Use and Misuse). Similar confirmation
was performed for each of the remaining ADAM sites for detected use of
marijuana (see Golub, Andrew, and Bruce D. Johnson, "Monitoring the
Marijuana Upsurge With DUF/ADAM Arrestees," final report submitted
to the U.S. Department of Justice, National Institute of Justice,
Washington, DC, 2000) and for detected use of cocaine (see Golub,
Andrew, and Bruce D. Johnson, Crack's Decline: Some Surprises Across
U.S. Cities, Research in Brief, Washington, DC: U.S. Department of
Justice, National Institute of Justice, July 1997, NCJ 165707).

d. Golub, Andrew, and Bruce D. Johnson, "Monitoring the Marijuana
Upsurge With DUF/ADAM Arrestees."

---------------------------

Andrew Golub and Bruce D. Johnson are, respectively, principal
investigator and director, Institutes for Special Populations Research, at
the National Development and Research Institutes, Inc. The authors'
research and their preparation of this Research in Brief were supported by
NIJ under grant number 99-IJ-CX0020, awarded to the National
Development and Research Institutes, Inc.

Findings and conclusions of the research reported here are those of the
authors and do not necessarily reflect the official position or policies of the
U.S. Department of Justice or the National Development and Research
Institutes, Inc.

The National Institute of Justice is a component of the Office of Justice 
Programs, which also includes the Bureau of Justice Assistance, the
Bureau of Justice Statistics, the Office of Juvenile Justice and Delinquency
Prevention, and the Office for Victims of Crime.

This and other NIJ publications can be found at and downloaded from the
NIJ Web site (http://www.ojp.usdoj.gov/nij).

NCJ 187490

---------------------------

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