Using Imaging to Assess Effects of THC on Brain Activity

This study will assess the effects of THC intoxication using dronabinol (synthetic THC) on the oxyhemoglobin (HbO) signal during resting state and task-based activation in the prefrontal cortex (PFC) and resting state connectivity, as well as on neurocognitive task performance and correlations between these measurements and clinical signs of intoxication. Participants will be 150 adults who use marijuana at least monthly (aged 18-55) will be recruited to participate in this study. Participants will be given up to 80 mg of dronabinol, an FDA-approved synthetic form of THC that is used to treat loss of appetite that causes weight loss in people with AIDS. THC is the principle psychoactive drug in marijuana. The study will be conducted in regular cannabis users who present at their first study visit with a positive urine screen for THC metabolites. Phase 2A. Investigate the effect of THC on fNIRS brain signature and its association with self-reported intoxication, laboratory measures of impairment, and the gold-standard behavioral field test of driving impairment used by law enforcement, the primary classifier. Phase 2B. Examine potential interaction following co-administration of THC with oral ethanol exposure in healthy volunteers. Phase II is a randomized, double-blind, placebo-controlled, 2 by 2 crossover study of effect of dronabinol, ethanol, and combined dronabinol and ethanol on brain activation and connectivity as measured by fNIRS.