Time course effects of marijuana and ethanol on event-related potentials.

Twelve male college students received orally on different days NIMH marijuana extract calibrated to contain 0.7 mg/kg delta-9-tetrahydrocannabinol, 1.0 ml/kg 95% ethanol, and placebo in a double-blind balanced-order design. The contingent negative variation (CNV), auditory evoked potential (EP), heart rate (HR), and subjective measures of intoxication were recorded prior to drug ingestion and at regular intervals for 4.5 h postdrug. Both drugs produced significant subjective effects. Marijuana increased HR but did not have a significant effect on CNV amplitude or EP peak amplitudes and latencies. Ethanol increased HR, but not significantly, and reduced CNV amplitude and N1-P2 amplitude. Time-action curves for ethanol's effect on subjective high, HR, and N1-P2 amplitude were parallel, peaking between 0.5 and 1.5 h postdrug and returning to baseline by the end of testing. Time-action curve for ethanol's effect on the CNV showed continuing amplitude reduction throughout the test session.