Alcoholism and drug abuse are major public health problems in many countries. In the United States, for example, it is estimated that 8–10% of men and 3–5% of women abuse or are dependent on alcohol, and that 5% of senior high school students consume alcohol on a daily basis (Bukstein, Brent & Kaminer, 1989; Group for the Advancement of Psychiatry, 1991; Schuckit, 1986). In 1985 there were over 500000 known heroin addicts in the United States, 5 million people were using cocaine, and at least 7 million were regularly using prescription drugs, mostly addictive ones, without medical supervision (Barchas et al., 1985).

The economic, social, and health consequences of psychoactive substance abuse are enormous. More than a decade ago, the estimated annual cost of alcohol and drug abuse to the economy of the United States was $177.4 billion (Group for the Advancement of Psychiatry, 1991). Substance abusers have high levels of morbidity and mortality from accidents and diseases, and also high prevalence rates of psychiatric disorders. In addition, the violent or other pathological behaviour of many substance dependent individuals frequently has adverse effects on the mental health of their spouses or children. Added to these sequelae in recent years is the rapid spread of HIV infection among intravenous drug users. Consequently, there is renewed interest in the treatment and prevention of substance use disorders with much of the current research focused on elucidating factors that increase peoples' risk for developing these disorders.