Cannabis abuse triples risk of psychosis: Study

By Ryan Maass  |  Nov. 8, 2016 at 3:00 PM
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OSLO, Norway, Nov. 8 (UPI) -- People who abuse marijuana may be more than tripling their risk for developing psychosis, researchers at the Norwegian Institute of Public Health say.

NIPH scientists partnered with other researchers from Virginia Commonwealth University to examine the relationship between the effects of cannabis and psychosis, a mental ailment marked by a detachment from reality and often bizarre behavior.

In effort to determine whether people living with psychosis are attracted to the drug, or if the drug itself is the cause of the disease, researchers conducted psychiatric interviews with Norwegian twins.

"Previous research has shown that patients with psychotic disorders use cannabis more often than the general population," researcher Ragnar Nesvåg said in a press release. "However research has been divided over whether cannabis use was the cause of the psychotic disorders."

The team says twins were chosen in the study in order rule out as many outside risk factors as possible. The twin studies revealed the twin with symptoms of cannabis abuse had a 3.5 times higher risk of developing psychosis-related symptoms.

"Our analyses showed a significant association between cannabis abuse and symptoms of psychosis in the general population," senior researcher Eivind Ystrom explained. "We also tested the hypothesis that symptoms of psychosis caused cannabis abuse, but the hypothesis was less suited to the data. Therefore, it appears that cannabis abuse can be a cause of psychosis."

Researchers say their findings should be considered by governments considering making cannabis more available through decriminalization or legalization.

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