Influence of treatment of Tourette syndrome with Delta(9)-tetrahydrocannabinol (Delta(9)-THC) on neuropsychological performance

Previous studies have suggested that marijuana (cannabis sativa) and delta- 9-tetrahydrocannabinol (Delta (9)-THC), the major psychoactive ingredient o f marijuana, are effective in the therapy of ties and associated behavioral disorders in Tourette Syndrome (TS). Because there is also evidence that c annabis sativa may cause cognitive impairment in healthy users, we performe d a randomized double-blind placebo-controlled crossover trial for Delta (9 )-THC in 12 adult TS patients to investigate whether treatment of TS with a single dose of Delta (9)-THC at 5.0 to 10.0 mg causes significant side eff ects on neuropsychological performance. Using a variety of neuropsychologic al tests, we found no significant differences after treatment with Delta (9 )-THC compared to placebo treatment in verbal and visual memory, reaction t ime, intelligence, sustained attention, divided attention, vigilance, or mo od. Only when using the Symptom Checklist 90-R (SCL-90-R) did our data prov ide evidence for a deterioration of obsessive-compulsive behavior (OCB) and a trend towards an increase in phobic anxiety. However, these results shou ld be interpreted with caution as SCL-90-R has known limitations on measuri ng OCB. We suggest that the increase in phobic anxiety is mainly due to the fact that a single-dose treatment rules out the possibility of administeri ng the dosage slowly. In contrast to results obtained from healthy marijuan a users, a single-dose treatment with Delta (9)-THC in patients suffering f rom TS does not cause cognitive impairment. We therefore suggest that furth er investigations should concentrate on the effects of a longer-term therap y of TS with Delta (9)-THC.