Changes in human event related potentials with prolonged delta-9-tetrahydrocannabinol (THC) use.

Auditory event related potentials and contingent negative variation (CNV) were recorded in a series of behavioral tasks from 27 hospitalized human volunteers before, early during (1--3 days), late during (10--14 days) and after chronic THC intoxication at two dose levels (70--90 mg/day or 180--210 mg/day in divided doses). Twelve additional hospitalized volunteers served as a control group. The N1 component of the auditory event related potential in all tasks was depressed when tested early during 180--210 mg/day THC administration. No N1 changes were seen for the subjects receiving 70--90 mg/day or the control subjects. Ten to 14 days during the chronic THC perioe CNV was depressed in all tasks except the control task for both doses at the early THC testing. Only at the most difficult task at the higher of the doses was the CNV depressed at the test late in the THC period. The changes seen in the N1 and the CNV may be indicative of different aspects of a common attentional alteration during stimulus processing. The results on our more difficult tasks suggest the alteration may continue in complex stimulus processing tasks in heavy marijuana users.