Problematic alcohol and cannabis use in adolescence--risk of serious adult substance abuse?

The aim of this longitudinal study was to investigate the problematic use of alcohol, cannabis or both in adolescence, identifying various risk factors for adult alcohol and drug abuse. The study included 7,577 18-year-old men conscripted in 1969-70. At enrollment, they completed two questionnaires about alcohol and drug use, social background, behavioural factors and health conditions. Data on adult alcohol and substance abuse were obtained from official registers up to 1996. A combination of problematic alcohol use and cannabis use in adolescence (>10 times) was associated more strongly with both adult alcohol abuse (RR=6.56, 95% CI 4.24-9.83) and drug abuse (RR=19.37, 95% CI 11.16-32.30) than adolescent use of cannabis or alcohol alone. When stratifying for different risk factors, the combination of both problematic alcohol use and cannabis use had higher relative risks of both outcomes than alcohol or cannabis use alone. In multivariate analyses, tobacco smoking was associated most strongly (RR=2.26, 1.58-3.24) with adult alcohol abuse, and a combination of problematic alcohol use and cannabis use (<10 times) in adolescence was associated most strongly with adult drug abuse (RR=5.60, 95% CI 2.92-10.75). Adolescent use of both cannabis and alcohol seems to be a more serious problem than adolescent use of either alcohol or cannabis alone with regard to escalation to adult alcohol and drug abuse. This is important knowledge for prevention of adult abuse. Special effort should be made to reach those who mix risky alcohol use and cannabis use in late adolescence.