Gender-related differences in diazepam effects on performance.

In order to investigate the possible differences of diazepam effects in the two sexes, two placebo-controlled double-blind studies were conducted on healthy volunteer students. In one study the subjects received diazepam 10 mg alone or combined with 0.5 g/kg of alcohol in a parallel group design; in the other 0.2 mg/kg of diazepam or placebo were given in a cross-over manner. In both trials diazepam impaired the psychomotor skills of women more than men. The difference was similar in tasks measuring cognitive (digit symbol substitution), motor (balance of extraocular muscles) and sensory (critical flicker fusion) performances. Tapping speed was affected to a similar degree in both genders. Diazepam 10 mg did not cause impairment of body balance, a parameter sensitive to alcohol. The combined effect of diazepam and alcohol was of similar magnitude in both sexes in all objective tests. Subjectively the women felt themselves clumsier than did the men. The calming effect was similar in both groups. The results suggest that while the performance of women may be more vulnerable than men to impairment by diazepam they also are aware of it. The difference of effects is of such magnitude that it may cause bias in experiments unless carefully balanced groups are used.