Benzodiazepines and vigilance performance: a review.

The literature on the effects of anxiolytic and hypnotic drugs on performance in tasks requiring sustained attention is confusing. This review is an attempt to evaluate the usefulness of vigilance tasks in the assessment of adverse effects of benzodiazepines. The long, monotonous, character of these tasks may be more relevant to many tasks performed in everyday life than the short, and often stimulating, tasks commonly employed in test batteries. From 37 available studies, 26 were examined in detail. In young, normal volunteers, vigilance tasks were found to be sensitive, often dose dependently, to the impairing effects of drugs, even in low doses (2.5 mg diazepam). With these subjects the tasks may be successfully used to compare different benzodiazepines with respect to residual activity. Both accuracy and speed of performance appear to be affected. However, in people actually using the drugs ("patients"), adverse effects on performance are usually not found. There is no evidence that benzodiazepines aggravate the vigilance decrement occurring under normal conditions. They do affect overall level of perceptual sensitivity, but show less effects on response criterion. The drugs do not seem to interact with anxiety or sleep quality in their effect on performance, but there are few studies with patients, and the assessment of anxiety is not without problems. It is unlikely that impairments in vigilance are simply a byproduct of global, sedative effects, but there is uncertainty regarding measures of general sedation. Developing tolerance with repeated doses has been noted only occasionally, but the opposite of tolerance, aggravated impairment, has also been reported.