Teenagers suffering from mental health disorders are at significantly higher risk of self-harm if they smoke cannabis, a large-scale study in the US has indicated.
The Ohio State University research found that young people with mood disorders such as bipolar disorder or depression who also smoke cannabis are more than three times more likely to self-harm than those who don’t.
Those who smoke cannabis are also at significantly increased risk of dying from any cause, being more than twice as likely to die of an unintended overdose, and more than three times as likely to be murdered.
Over the course of seven years, the study tracked more than 200,000 people with mood disorders between the ages of ten and 24, and more than ten per cent of the study’s cohort were cannabis users.
These findings should be considered as states contemplate legalizing medical and recreational marijuana, both of which are associated with increased cannabis use disorder.
Lead author Dr Cynthia Fontanella said: “Marijuana use and addiction is common among youth and young adults with mood disorders, but the association of this behavior with self-harm, suicide and overall mortality risk is poorly understood in this already vulnerable population”.
She added: “These findings should be considered as states contemplate legalizing medical and recreational marijuana, both of which are associated with increased cannabis use disorder.”
Dr Fontanella confirmed cannabis use disorder was “significantly associated with self-harm, including death by unintentional overdose and homicide”, although she said the study was observational, and so it is “unable to contribute to our understanding of causality or mechanism”.
The study warned that young people with mental health issues could exacerbate their conditions by using the drug, and that it could also interfere with treatments.