Study: Marijuana Linked to Early Onset of Psychosis

A new study suggests marijuana may accelerate the onset of psychotic disorders in some young users, Reuters reported Feb. 7.

Matthew Large and colleagues at the University of New South Wales in Sydney, along with investigators at two U.S. sites, conducted an exhaustive review of the literature examining the effects of marijuana, alcohol, and other drugs on the onset of psychiatric disorders such as schizophrenia. Eighty-three studies involving more than 22,000 patients met inclusion criteria.

Past research has shown that one in every 100 Americans develops schizophrenia in his or her lifetime, with symptoms typically surfacing in the late teens or early 20s for men and in the late 20s and early 30s for women.

The researchers found patients with psychotic disorders who smoked marijuana at an early age developed symptoms almost three years sooner than those who did not. The link was strongest among those who started smoking at ages 12 to 15 or younger.

It is important to point out that most people who use marijuana do not become psychotic, according to Michael T. Compton, M.D., a behavioral scientist at George Washington University Medical Center in Washington, DC, and a coauthor of the paper. Nevertheless, these results strengthen the link between marijuana and the development of psychiatric diseases, and may even point to a causal relationship for some users, he said.

Public health officials are missing the mark by focusing on the dangers of marijuana use among older users rather than adolescents, according to the authors.

“Psychotic illnesses are horrible for the people who have them, and terrible for their families too,” said Large.  “An extra 2 or 3 years of psychosis-free functioning could allow many patients to achieve the important developmental milestones” of adolescence, concluded the authors.

The study was published online on Feb. 7 in the Archives of General Psychiatry.