Predictors of illicit substance dependence among individuals with alcohol dependence

Individuals with alcohol dependence (AD) are at increased risk for developing dependence on illicit and prescription drugs. The goal of this cross-sectional study was to identify factors associated with drug dependence among individuals with AD.

The sample consisted of 855 adults from the Irish Affected Sib Pair Study of Alcohol Dependence who were treated in inpatient or outpatient alcohol treatment programs and met Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, criteria for lifetime AD. We studied predictors of dependence on six classes of drugs: cannabis, sedatives, stimulants, cocaine, opioids, and hallucinogens. Potential predictors examined included gender, age, education, and socioeconomic status; the personality traits of extraversion, neuroticism, and novelty seeking; conduct disorder, major depressive disorder, nicotine dependence, age at onset of alcohol use, early illicit drug use, and parental AD.

Nicotine dependence, depression that began before substance use, and drug use before age 19 each increased the risk for dependence on several substance classes. Male gender, younger age, maternal AD, fewer years of education, higher neuroticism scores, conduct disorder, and early alcohol use each increased the risk of dependence on one or more substance classes.

Among individuals in treatment for AD, cigarette smoking, early onset of major depression, and early drug use were associated with increased risk for drug dependence. These results suggest individuals with these risk factors may benefit from more intensive screening to prevent the onset of or to identify and treat drug dependence.