Quitting cannabis use in your 20s significantly reduces the chance of progressing to other illicit drugs, according to research published in the Journal of Epidemiology and Community Health.
The study from the National Drug and Alcohol Research Centre (NDARC) at the University of New South Wales found that while cannabis use among Australians declines throughout their 20s, regular users have an increased risk of using other drugs compared with occasional users.
While never having used cannabis was the most protective of uptake of any substance, licit or illicit, cannabis users who quit in their 20s were a third to half as likely to take up illicit drugs cocaine, ecstasy and amphetamine as occasional users.
Those who used weekly were two to three times more likely to start using illicit drugs than occasional users. Daily users were six times as likely to start smoking cigarettes and were also less likely to give up all other drugs except cocaine.
Those who had never used cannabis were the least likely to begin using any other drugs, and were most likely to give up cigarette smoking and high-risk drinking in their 20s. At any point in time use of amphetamine, cocaine or ecstasy was virtually non-existent among non-users of cannabis.
The findings are based on secondary analyses of a landmark study of nearly 2,000 Victorian secondary school students who have been followed up and interviewed over 13 years, starting in 1992.
Lead author of the study, Dr Wendy Swift from NDARC, said that while most studies on the relationship between cannabis and other drug use have focused on adolescents this study is one of the first to look at what happens to cannabis users as young adults aged up to 29 years.
This study provides compelling evidence of the continuing association between cannabis, licit and other illicit drug use well into young adulthood, conclude the authors. Findings from this study suggest discouraging users from increasing their use and assisting them to quit altogether have great potential to reduce harms associated with both licit and illicit drugs in young adults.