It's a well-known fact that many young people use cannabis, and studies have pointed to a link between the drug and psychiatric conditions such as schizophrenia. However, the links between cannabis use and the development of bipolar symptoms over time have been insufficiently studied — until now.
Using regression analysis, the scientists adjusted for gender, alcohol and other drug use, early environmental risk factors — such as childhood adversity or abuse — and depression and psychosis at the age of 18.
The study found that using cannabis at least two or three times per week was a strong predictor for hypomania in early adulthood.
The authors conclude:
"Adolescent cannabis use may be an independent risk factor for future hypomania, and the nature of the association suggests a potential causal link. As such it might be a useful target for indicated prevention of hypomania."
Dr. Marwaha comments on the findings, saying, "Cannabis use in young people is common and associated with psychiatric disorders. However, the prospective link between cannabis use and bipolar disorder symptoms has rarely been investigated."
According to the latest statistics from the National Institute on Drug Abuse, over 35 percent of 12th graders — who are usually 17–18 years old — said that they used marijuana in the year leading up to the survey, and 6 percent admitted to using it "daily or near-daily."