Cohort trends in the age of initiation of drug use in Australia.

AIM To examine birth cohort trends in the prevalence of use and the age of initiation of use of: alcohol, tobacco, cannabis, amphetamines, LSD, and heroin. METHOD Data were taken from the 1998 National Drug Strategy Household Survey, a survey of a representative sample of Australians aged 14 years and over. Nine five-year cohorts were examined among persons born between 1940 and 1984. The weighted prevalence of use by ages 15 years, 21 years, and lifetime use, was estimated, as was the average age of first use among users. The significance of trends was tested using logistic regression (for lifetime use, use by 15 and 21 years) and linear regression (for age of first use). RESULTS Lifetime prevalence of alcohol and tobacco use was similar among all birth cohorts. The prevalence of illicit drug use--cannabis, amphetamines, LSD and heroin--increased with successive birth cohorts and more recent birth cohorts reported using licit and illicit drugs at a younger age. CONCLUSIONS More recent cohorts are more likely to use illicit drugs at some point in their lives. Greater numbers of persons from more recent birth cohorts may be at risk of developing substance-related problems.