Who are the new amphetamine users? A 10-year prospective study of young Australians

Despite good evidence of increased availability and use of amphetamines world-wide, relatively little is known about the epidemiology of young adult amphetamine use; relationships with social functioning, other drug use and mental health at this age; nor of the adolescent predictors of such use. We examined these issues using a representative cohort of young people followed-up in Victoria, Australia.

A stratified, random sample of 1943 adolescents was recruited from secondary schools across Victoria at age 14-15 years. This cohort was interviewed on eight occasions until the age of 24-25 years (78% follow-up at that age). Cross-sectional and predictive associations were assessed using logistic regression.

At age 24 years, 12% of the sample had used amphetamines in the past year, with 1-2% using at least weekly. Young adult amphetamine use was predicted strongly by adolescent drug use and was associated robustly with other drug use and dependence in young adulthood. Associations were stronger for more frequent users. Among young adults who had not been using amphetamines at age 20 years, the strongest predictor of use at age 24 years was the use of other drugs, particularly cannabis, at 20 years. Psychological distress did not predict independently an increased likelihood of amphetamine use in this cohort.

Young people in Australia using amphetamine at age 24 years are highly likely to be significant polydrug users. The risks for both initiation of young adult amphetamine use, and maintenance of such use, pertain to the heavy use of other drugs. Interventions for heavy amphetamine users at this age are likely to require attention to multiple drug problems.