Weekly cannabis use is more than seven times more likely in people with mental illness when compared to people without a mental illness, according to a study announced on April 2, 2013, by the Centre for Addiction and Mental Health (CAMH). The study was published in the journal “Comprehensive Psychiatry.”
People with mental illness are also 10 times more likely to be diagnosed with a cannabis use disorder. Researchers also found that the rate of cannabis use was higher in patients with personality disorders, bipolar disorder, and other substance use disorders.
An estimated 203 million people use cannabis, the most widely used illicit substance in the world. Past research has linked cannabis use and mental illness, but the study is first to investigate the actual numbers and prevalence of the substance use.
"We know that people with mental illness consume more cannabis, perhaps partially as a way to self- medicate psychiatric symptoms, but this data showed us the degree of the correlation between cannabis use, misuse, and mental illness," said Dr. Shaul Lev -ran, Adjunct Scientist at CAMH and Head of Addiction Medicine at the Sheba Medical Center, Israel.
"Based on the number individuals reporting weekly use, we see that people with mental illness use cannabis at high rates. This can be of concern because it could worsen the symptoms of their mental illness," said Lev-ran, who conducted the research as a post-doctoral fellow with the Social Aetiology of Mental Illness (SAMI) Training Program at CAMH.
CAMH researchers analyzed U.S. data from face –to-face interviews with more than 43,000 participants over the age of 18 from The National Epidemiologic Survey on Alcohol and Related Conditions.
In the past 12 months, 4.4 percent of mentally ill individuals reported that they used cannabis weekly. Only 0.6 percent of individuals without mental illness reported cannabis use. The substance use was pervasive in most age groups and generally higher among young people.
Researchers emphasized the importance of medical practitioners screening people with mental illness for substance use so that prevention and intervention measures can be implemented.
