Effects of abused drugs on psychomotor performance

Some abused drugs have been reported to alter performance on naturalistic tasks such as driving and also on laboratory tasks. The performance effects of several drug classes were examined using a repeated measures design. Eight volunteers were administered 2 doses of ethanol, marijuana, amphetamine, hydromorphone, pentobarbital, or placebo on separate days. The larger dose of each increased subjective drug strength; however, only ethanol and pentobarbital impaired performance on circular lights, digit symbol substitution, and serial math tasks. Both ethanol and pentobarbital impaired performance on card-sorting tasks; impairment was evident at lower doses as the cognitive load increased. Results illustrate differences among drugs in producing performance impairment at doses that cause subjective effects. Increasing cognitive requirements uncovered performance impairment at lower doses.