Benzodiazepine‐induced reduction in activity mirrors decrements in cognitive and psychomotor performance

Objective To assess whether actigraphy is sensitive to benzodiazepine‐induced changes in cognitive and psychomotor performance and sleep. Methods Healthy young volunteers ( n  = 23; 11 males), were randomised to a double‐blind, placebo‐controlled, crossover trial. Actigraphy was used to record motor activity continuously. Following dosing at 18.00 h with 2.5 mg lorazepam (LZP), psychomotor and cognitive assessments were made at hourly intervals post‐dose for 4 h and after sleep at 14.5 h post‐dose. Results Activity levels were significantly reduced after LZP for 5 h post‐dose ( p  = 0.0104), during sleep (5–13 h) ( p  < 0.02) and the following morning, 13–14.5 h post‐dose ( p  < 0.02). At the same time cognitive and psychomotor performance was also significantly impaired ( p  < 0.05). LZP also significantly increased actigraphic sleep efficiency and sleep per cent ( p  < 0.02). Conclusion This study showed that activity levels were significantly reduced following dosing with a benzodiazepine and these changes coincided with impairment of cognitive and psychomotor performance. Actigraphy, therefore, appears to be able to reflect the psychopharmacological effects of a benzodiazepine in changes in daytime function and nocturnal behaviour, which, without waking the subject, is beyond the power of conventional psychometrics. Copyright © 2008 John Wiley & Sons, Ltd.