Neurocognitive and Psychiatric Consequences of Cannabis Use

Cannabis (THC) is the most widely used illicit drug in America. Although the acute effects of THC on neuropsychological functions are reversible, long-term neurocognitive effects and potential psychiatric consequences are not yet fully understood. However, it is important to specify the potential long-term effects of cannabis for several reasons: (1) THC might be used as a treatment for certain conditions in the future, so it is important to determine whether or not THC produces long-lasting neurotoxicity; (2) THC use among young people may lead to irreversible outcome including cognitive deficits and is implicated in increased risk for schizophrenia but it is rather unclear whether pre-existing liability for psychosis may be a major factor.

We are examining neurocognitive and psychiatric consequences of THC use in young adults with respect to attention, inhibitory control, and social cognition in current and past cannabis users and nonusers at the beginning of the first year of college. They are monitored regularly over the course of one year to track changes in behavior in relation to THC use. In addition, schizotypal personality is assessed at baseline and a year later to test whether THC use increases psychosis-proneness or if pre-existing schizotypal personality increases the probability of using THC. Past studies have not been able to adequately address this question.

In sum, this project will enable us to further identify the potential neurocognitive and psychiatric consequences of THC in young, healthy people and pinpoint possible neural circuits that may be affected by THC. The outcome of this project will enable us to conduct focused functional and structural neuroimaging studies of adolescent and young adult THC users in the future in order to understand how THC use may affect neural circuits in late adolescence and early adulthood and whether these potential changes are permanent. Thus the outcome of this proposal will directly form the basis for systematic neuroimaging investigations of the origins of THC neurotoxicity and THC’s potential role in psychosis.

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