Regular use of cannabis in adolescence is associated with anxiety disorders in young adulthood, shows an Australian study.
However, the authors found no association between adolescent cannabis use and depression in young adulthood.
The findings arise from a nine-wave study (six in adolescence and three in young adulthood) involving nearly 2000 individuals (53% female) who were recruited in secondary school. Participants were surveyed at each wave from their midteens into their late-twenties.
Psychiatric morbidity was assessed at each adolescent wave with the Revised Clinical Interview Schedule, and at 29 years using the Composite International Diagnostic Interview-defined International Classification of Diseases (ICD)-10.
As reported in Addiction, the researchers found no significant association between adolescent cannabis use and depression at age 29 years. But daily cannabis users were 2.3 times more likely to have an anxiety disorder in young adulthood than nonusers.
Individuals who were cannabis-dependent (at least weekly cannabis use in young adulthood) were 2.5 times more likely to have an anxiety disorder at age 29 years than those who were not dependent. These effects remained after controlling for other concurrent drug use and adolescent anxiety/depression.
Louisa Degenhardt (University of New South Wales, Sydney, Australia) and co-investigators also report that there appeared to be an increased risk for anxiety disorders at age 29 years among adolescent cannabis users, even if they ceased using cannabis in adulthood.
The team notes that it is possible that other confounding variables could explain these observed associations. "It is possible, for example, that continued and/or escalating cannabis use is a marker for other life-course features that are also associated with an increased risk of anxiety, such as impaired social role transitions and unemployment," they say.
"Further work is required to… clarify whether there is a causal relationship between early heavy cannabis use and anxiety disorders, or whether this association is better explained by residual confounding by social context or temperament."
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