Psychosis Risks with Marijuana Use

At a recent conference Robin Murray, a researcher based in London, gave a talk about the potential adverse effects of tetrahydrocanabinol (THC). Considerable data indicate that chronic long-term smoking of marijuana is associated with the doubling of the risk of psychosis. Moreover, if a marijuana user has a common genetic variant in the catechol-o-methyltransferase enzyme (COMT), they are at substantially increased risk for the development of psychosis. New data also indicate that frequent use of marijuana can also be associated with an earlier onset of schizophrenic psychosis than would ordinarily occur without the substance use. Data also suggest that the psychosis associated with THC use is more difficult to treat than that without such use.

Murray also reported on a new risk that is associated with more potent new products. Older, natural forms of marijuana contained a compound called cannabidiol, which is associated with calming effects and possible antipsychotic effects. In a new synthetic preparation of THC called skank or spice, there is a higher amount of THC, but none of the positive diol compound. Thus there are some important caveats to the prevailing view that marijuana is relatively harmless.

Editor’s Note: Marijuana use brings a clear-cut increased risk for psychosis, which appears to interact with a common gene polymorphism and which is increased with use of a new synthetic preparation called skank or spice. If a marijuana user has a concurrent mood disorder, the risks appear to be even greater. The one sure pharmacological effect of marijuana is an amotivational syndrome, and motivational deficits are one of the core components of depression.

Given the difficulty of treating the mood and schizophrenic disorders, a patient should not risk worsening their illness with marijuana. N-acetylcysteine is one treatment option that may bring about decreased craving for and avoidance of marijuana and a number of other abused substances, as well as being helpful for mood and negative symptoms in schizophrenia.

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