Differences in rapid eye movement (REM) sleep abnormalities between posttraumatic stress disorder (PTSD) and major depressive disorder patients: REM interruption correlated with nightmare complaints in PTSD

Abstract Objective The presence of repeated nightmares in posttraumatic stress disorder (PTSD) has been hypothesized as a dysfunction of rapid eye movement (REM) sleep, but there has been remarkably little agreement about the pathophysiology. This presents a deterrent to more effective treatments. REM sleep abnormalities including elevated REM density also have been replicated in major depressive disorder (MDD). The purpose of this study was to clarify the difference of REM sleep abnormalities between the two disorders for understanding the pathophysiology of sleep disturbances in PTSD. Methods Polysomnographic measures were compared among 14 PTSD patients (aged 23.7 ± 5.5 years) and 14 MDD patients (aged 27.9 ± 10.1 years) under drug-naive or drug-free conditions. We defined REM interruption by summing the intrusive wake times during the REM period and adding the subsequent wake times to the last epoch of REM period. The significant polysomnographic measures were correlated with PTSD symptoms within the PTSD group. Results REM interruption was significantly increased in the PTSD group compared with the MDD group (12.2 vs 2.1 min, p = 0.001). REM density was also significantly increased in the PTSD group compared with the MDD group (30.5 vs 23.1%, p  = 0.019). Within the PTSD group, we found significant correlations between the severity of trauma-related nightmare complaints and the percentage of REM interruption ( R  = 0.62, p  = 0.017), but not REM density. Conclusions REM sleep abnormalities are different between PTSD and MDD. Increased REM interruption may be a biological marker correlated with nightmare complaints in PTSD patients. Treatments including pharmacotherapy that reduces REM interruption might ameliorate nightmares in PTSD.