In collecting data, the authors used interviews, questionnaires, and objectives tests of psychological functions. Instruments were designed to meet research objectives and meet specific local conditions. Survey research between 1957 and 1974 focused on correlations between cannabis use and various psychosocial factors; beginning in 1975, research was redirected to concentrate on the epidemiology of drug abuse. Because of cultural considerations, the only women subjects were university students, while male subjects ranged across the socioeconomic spectrum. The most recent surveys show that 30 percent of male industrial workers and 20 percent of male students have used drugs at some time. The respondents ranked alcohol as the most frequently abused substance, followed by cannabis and opiates, and psychotropic substances. Alcohol and cannabis use generally occurred initially during social situations, while the first use of psychotropic substances was often an attempt to cope with physical or mental stress. The authors contend it is the drug users, rather than the non-users, who hear about drugs, see drugs and have personal friends and relatives who themselves abuse drugs. 28 references. (Author abstract modified)