Occasional cannabis a path to harder drugs

OCCASIONAL use of cannabis in adolescence increases the risk of illicit drug use in adulthood and could lead to low educational achievement, Australian research suggests.

A study of almost 2000 Victorian secondary school students found those who used cannabis infrequently (less than once a week) had higher rates  of alcohol and tobacco dependence and illicit drug use 10 years later than non-users. They were also less likely to have completed post-school qualifications by the age of 24. 

Lead author Professor Louisa Degenhardt, from the National Drug and Alcohol Research Centre at the University of NSW, said: “It seems clear that in countries such as Australia, where cannabis use is the norm among young people, even infrequent cannabis use is related to later levels of drug use of all kinds. 

“Whether this is due to learning processes, the influence of social networks or other factors... early onset occasional cannabis use is a marker for later drug use and drug problems.” 

A third of students in the study reported using cannabis in the past six months; 36% of these were regular users and 64% occasional. 

Lower educational attainment among occasional cannabis users was significantly attenuated after adjusting for tobacco use, suggesting a possible link between general risk-taking behaviours and adverse psychosocial outcomes, the authors said.

Br J Psychiatry 2010 296: 290-95