Anti-Intrusion Effect of Lorazepam: An Experimental Study

OBJECTIVE: Easy triggering of trauma-related episodic memory fragments caused by perceptual cues is tied to strong perceptual priming in the implicit memory system. And among benzodiazepines, only lorazepam has been consistently reported to have an atypical suppression effect on perceptual priming processes. The aim of this study was to investigate the effects of single doses of lorazepam, diazepam, and a placebo on intrusive memories after exposure to a distressing videotape and to explore whether the anti-intrusive effect of lorazepam is acquired as a result of the suppression of perceptual but not conceptual priming processes. METHODS: Under prospective, randomized, and double-blind conditions, we compared the anti-intrusion effect of a single dose of lorazepam (n=22) with that of diazepam (n=22) and a placebo (n=21) in young healthy Korean college students following exposure to a traumatic videotape. RESULTS: We present the first finding for an anti-intrusion effect of lorazepam. One day after the medication, lorazepam, rather than diazepam or the placebo, significantly reduced the extent of intrusion and data-driven processing of the traumatic information. There were no differences among the three conditions in state anxiety, depression, and an arousal scale throughout the experiment. CONCLUSION: Results from this study suggest the possibility of lorazepam as a candidate anti-intrusion drug, as well as the cautious use of diazepam in the treatment of PTSD patients. The anti-intrusive effect of lorazepam is directly related to its atypical inhibitory effect on implicit perceptual priming processes. The present study provides support for the enhanced perceptual priming hypothesis of PTSD.