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Study Finds Mental Illness Associated With Heavy Cannabis Use

Mentally ill individuals seven times more likely to use cannabis weekly (Apr. 2)

People with mental illnesses are more than seven times more likely to use cannabis weekly compared with people without a mental illness, according to researchers at Canada’s Center for Addiction and Mental Health (CAMH), who studied U.S. data.

Cannabis is the most widely used illicit substance globally, with an estimated 203 million people reporting use. Although research has found links between cannabis use and mental illness, the exact numbers and prevalence of problem cannabis use had not been investigated.

“We know that people with mental illness consume more cannabis, perhaps partially as a way to self-medicate psychiatric symptoms, but these data showed us the degree of the correlation between cannabis use, misuse, and mental illness,” said Dr. Shaul Lev-ran, who led the research as a post-doctoral fellow at CAMH.

“Based on the number of 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,” Lev-ran said.

The researchers also found that individuals with mental illness were 10 times more likely to have a cannabis use disorder.

In the new study, published in Comprehensive Psychiatry, researchers analyzed data from interviews with more than 43,000 respondents over the age of 18 years from the National Epidemiologic Survey on Alcohol and Related Conditions. Using questionnaires, the researchers assessed cannabis use as well as various mental illnesses, including depression, anxiety, drug and alcohol use disorders, and personality disorders, based on criteria from the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV).

Among respondents who reported at least weekly cannabis use, the rates of use were particularly high for those with bipolar disorder, personality disorders, and other substance-use disorders.

In total, 4.4% of individuals with a mental illness in the past 12 months reported using cannabis weekly, compared with 0.6% of individuals without mental illness. Cannabis use disorders occurred in 4.0% of those with mental illness versus 0.4% of those without.

The researchers also noted that, although cannabis use is generally higher among younger people, the association between mental illness and cannabis use was pervasive across most age groups.

The investigators emphasize the importance of screening for frequent and problem cannabis use among individuals with mental illness so that targeted prevention and intervention strategies may be employed.

Source: CAMH; April 2, 2013.

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