The abuse of substances is a complex problem that involves multiple substances, changing consumption patterns over time, and the emergence of biopsychsocial problems that culminate in substance use disorders (SUD). These substances include nicotine, alcohol, amphetamines, and similarly acting sympathomimetics, cannabis, cocaine, hallucinogens, inhalants, opioids, phencyclidine and similarly acting arylcyclohexylamines, and sedatives, hypnotics, or anxiolytics. Changes in substance use occur during the natural history of consumption. Relevant factors include initiation, type and amount of drug consumed per episode, and problems that take place as a result of consumption. It is therefore appropriate to develop a comprehensive assessment of substance involvement in order to understand the progression from substance use behavior to substance abuse disorder. At the Center for Education and Drug Abuse Research (CEDAR), a comprehensive approach to assessing substance abuse involvement was developed. This article describes the evaluation process called the “diachronic” assessment protocol. The term diachronic is concerned with the study of changes that take place over time. CEDAR developed a protocol that provides detailed chronologies of substance use and related problems leading toward a substance abuse disorder. Lifetime alcohol and drug history is defined as the number of episodes of substance use within a specified time frame. Drug and alcohol history charts were designed to measure substance use patterns, record changes in substance use patterns and the reasons for the changes, and map transition from substance use to abuse and dependence. Twelve variables are used in the assessment protocol across each phase: 1) Drug use list; 2) Phase definition; 3) Quantity and frequency; 4) Route of administration; 5) Style; 6) Time; 7) Place; 8) Social Context; 9) Substance abuse consequences; 10) Desire to use again; 11) Variation; and 12) Variation reasons. Among the findings were that antisocial behavior and negative affect characterized boys who were at a high risk for SUD. The authors’ found that the chronology of the father’s SUD was an important factor on the child’s adjustment. Another finding is that children using tobacco prior to adolescence, and children with disruptive behavior disorders led to adolescent substance abuse. The first manifestation of substance abuse problems usually occurred in mid-adolescence. At this time, a small number of subjects had achieved the age to undergo late adolescent and young adult assessments. The strength of the CEDAR is that it has been shown to have predictive value. Thus it is useful in understanding the etiology of SUD and, in particular, for charting the SUD outcome. References