Pot smoking linked to psychotic disorders
Heavy marijuana use doubles the risk, new research finds.
By Jia-Rui Chong
L.A. Times Staff Writer
July 27, 2007
People who smoke marijuana daily or weekly double their risk of developing a psychotic illness over their lifetime, according to a study published Thursday.
Among all cannabis users, including sporadic experimenters and habitual users, the lifetime risk of psychotic illness increased by 40%, the report said....
The study by Zammit and colleagues, published in the medical journal the Lancet, reanalyzed data from seven long-term studies on psychotic illnesses and marijuana involving 61,000 participants.
The researchers filtered out about 60 factors, such as preexisting mental illness and the use of other illicit drugs, and considered IQ and social class, to try to isolate the effect of marijuana, Zammit said.
Most of the studies that were analyzed indicated a range of increased risk for frequent users from 50% to 200%, with the average being about 100%, or double the risk, [Dr. Stanley] Zammit said.
The researchers also studied the relationship between marijuana use and mood disorders, such as depression and bipolar disorder. They analyzed 22 studies involving 52,000 participants.
The researchers found that any marijuana use increased the lifetime risk for mood disorders by about 40%, and weekly or daily use increased the risk by about 50%.
RESEARCHERS at Cardiff University also said they were unable to conclusively link heavy marijuana use to the so-called "one sentence, one paragraph" craze currently sweeping Los Angeles and other centers of "hippie" culture.