Heavy Marijuana Use Linked to Mental Illness

A new study from Denmark adds to concerns about the impact of marijuana upon users’ mental health.

According to a Wall Street Journal op-ed by psychologist Susan Pinker, a mammoth study of the health records of all 6.5 million Danes over a 26-year period showed a strong correlation between cannabis (marijuana) use disorder and various mental health diagnoses. (According to Pinker, “cannabis use disorder” can be defined as “craving marijuana, using it more often than intended, spending a lot of time using it, and having it interfere with friends, family and work.” The Centers for Disease Control state that approximately 30% of American marijuana users develop cannabis use disorder.) The study showed that persons diagnosed with cannabis use disorder were nearly two times as likely to later be diagnosed with clinical depression. Furthermore, the study indicated that persons with cannabis use disorder “were up to four times as likely to be diagnosed later with bipolar disorder with psychotic symptoms.” The study also found that the amount of cannabis a person consumed was directly correlated with a higher risk of bipolar disorder with psychotic symptoms. While Pinker cautioned that the study did not answer the question of whether heavy cannabis use leads to mental illness or whether mentally ill people are more likely to use cannabis, its findings are striking.

Some marijuana users may dismiss a study like this one on the grounds that their usage of marijuana has not become an addiction, and that the study’s findings are irrelevant to their lives. The truth, however, is that no marijuana user knows for certain whether he or she will develop an addiction to the substance.

Marijuana is a dangerous drug, and it places the physical and mental health of users at risk.