Regular use of marijuana could more than triple a person’s chance of developing a psychotic disorder, a new study suggests.
Researchers from the Norwegian Institute of Public Health (NIPH) and from Virginia Commonwealth University interviewed Norwegian twins in order to look at the relationship between psychosis and cannabis. Psychosis is characterized as a detachment from reality and bizarre behavior.
“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 researchers picked twins for their study in order to rule out the risk of genetic irregularities or other factors, which may skew the results.
“The relative importance of genes in the causes of a disease is known as heritability, and we know from previous studies at the NIPH that cannabis abuse is very heritable,” said Eivind Ystrom, senior researcher at NIPH.
By studying twins, they were able to test the theory that marijuana can lead to psychotic symptoms and that psychotic symptoms could also lead to abusing cannabis. What the researchers found was that abusing marijuana led to symptoms of psychosis. In fact, the twin that abused cannabis was 3.5 times more likely than their sibling to develop symptoms of psychosis.
“Our analyses showed a significant association between cannabis abuse and symptoms of psychosis in the general population,” said Ystrom. “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.”
Previous studies have found that cannabis abuse is heritable, which was also confirmed in their analysis.
“As much as 88 percent of the causes of why some people abused cannabis, yet others did not, could be attributed to some people having risk genes,” the press release read.
However, after the genetic risk and childhood environment were accounted for, people who abused marijuana still had a multiplied chance of developing symptoms of psychosis.
The study’s authors urged lawmakers to consider their findings when preparing policies or legislation regarding marijuana.
Despite this possible connection between marijuana and psychotic disorders, cannabis has been linked to a myriad of health benefits. Studies have shown that marijuana can be used for pain relief, treating depression, preventing epileptic seizures, and reducing brain damage after a stroke. A 2007 study even found that cannabidiol, a chemical found in marijuana, can stop cancer from spreading by turning off a gene called Id-1.
Danielle Tarasiuk is a multimedia journalist based in Los Angeles. Her work has been published on AllDay.com, Yahoo! Sports, KCET, and NPR-affiliate stations KPCC and KCRW. She’s a proud Sarah Lawrence College and USC Annenberg alumn.