Acute effects of lorazepam on laboratory measures of aggressive and escape responses of adult male parolees.

Acute benzodiazepine administrations typically decrease aggressive responding, but increases in aggression have been reported in some studies. The benzodiazepine lorazepam has been studied less frequently than other benzodiazepines in aggression research, although it is often used to suppress violent aggression in patients. The present study was designed to investigate the effects of acute administrations of lorazepam on aggressive responding in adult humans on a laboratory aggression task. Eight adult males participated in experimental sessions on the Point Subtraction Aggression Paradigm (PSAP), which provided subjects with aggressive, escape and monetary-reinforced response options. Acute oral doses (1, 2 and 4 mg) of lorazepam decreased both aggressive responding and monetary-reinforced responding in seven of eight subjects. In one subject, lorazepam produced dose-dependent increases in aggressive responding. The effects of lorazepam on escape responding were the same as the effects on aggressive responding. The results are consistent with prior research using the PSAP and clinical data showing that benzodiazepines generally decrease aggression, and contrast with other studies that have shown that benzodiazepines can increase aggression. Since lorazepam affected both aggressive and escape responding, it is suggested that while lorazepam often produces sedation, it also modifies human aggressive responding, in part, by suppressing reactions to aversive stimuli.