Study: Marijuana Can Produce Schizophrenia-Like Symptoms

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New research suggests that delta-9-THC, the principal active ingredient in marijuana, can cause transient schizophrenia-like symptoms, such as suspiciousness, delusions, and impairments in memory and attention.

The study, led by D. Cyril D'Souza, M.D., associate professor of psychiatry at Yale School of Medicine, set out to explore a long-known association between cannabis and psychosis.

"Just as studies with amphetamines and ketamine advanced the notion that brain systems utilizing the chemical messengers dopamine and NMDA receptors may be involved in the pathophysiology in schizophrenia, this study provides some tantalizing support for the hypotheses that the brain-receptor system that cannabis acts on may be involved in the pathophysiology of schizophrenia," said D'Souza. "Clearly, further work is needed to test this hypothesis."

For the study, researchers administered varying doses of delta-9-THC to participants who were screened for any vulnerability to schizophrenia. Some participants showed signs of schizophrenia that lasted about a half hour to one hour after being given THC. Symptoms included suspiciousness, unusual thoughts, paranoia, thought disorder, blunted affect, reduced spontaneity, reduced interaction with the interviewer, and problems with memory and attention.

The study was published June 2 on the website of the journal Neuropsychopharmacology.