Sleep Pathophysiology in Posttraumatic Stress Disorder and Idiopathic Nightmare Sufferers Anne Germain and Tore A. Nielsen Background: Nightmares are common in posttraumatic stress disorder (PTSD), but they also frequently occur in idiopathic form. Findings associated with sleep distur- bances in these two groups have been inconsistent, and sparse for idiopathic nightmares. The aim of the present study was to investigate whether sleep anomalies in PTSD sufferers with frequent nightmares (P-NM) differ from those observed in non-PTSD, idiopathic nightmare (I-NM) sufferers and healthy individuals. Methods: Sleep measures were obtained from nine P-NM sufferers, 11 I-NM sufferers, and 13 healthy control subjects. All participants slept in the laboratory for two consecutive nights where electroencephalogram, electro- oculogram, chin and leg electromyogram, electrocardio- gram, and respiration were recorded continuously. Results: Posttraumatic nightmare sufferers had signifi- cantly more nocturnal awakenings than did I-NM sufferers and control subjects. Elevated indices of periodic leg movements (PLMs) during rapid eye movement (REM) and non-REM sleep characterized both P-NM and I-NM sufferers. Conclusions: Posttraumatic nightmare sufferers exhibit more nocturnal awakenings than do I-NM sufferers and control subjects, which supports the hypothesis of hyper- arousal in sleep in PTSD sufferers; however, elevated PLM indices in both P-NM and I-NM sufferers suggest that PLMs may not be a marker of hyperarousal in sleep of PTSD sufferers. Rather, PLMs may be a correlate of processes contributing to intense negative dreaming. Biol Psychiatry 2003;54:1092–1098 © 2003 Society of Biological Psychiatry Key Words: Idiopathic and posttraumatic nightmares, sleep disturbances, periodic leg movements in sleep Introduction R apid eye movement (REM) sleep disturbances and nightmares have been suggested to be the hallmark of posttraumatic stress disorder (PTSD) (Ross et al 1989). The presence of REM sleep disturbances remains equiv- ocal, however, and no profile of sleep disturbances unique to PTSD has yet been established (e.g., see Pillar et al 2000 for review). One study showed that the nature of posttraumatic nightmares may shape sleep profiles in PTSD inpatients (Woodward et al 2000). Nightmares are part of the intrusion symptom cluster of PTSD (American Psychiatric Association 1994) and are reported by as many as 75% of PTSD patients (e.g., Kilpatrick et al 1994). Although spontaneous awakenings following distressing dreams are rarely observed when PTSD patients sleep in a laboratory environment, chronic and frequent distressing dreams (associated or not with a sudden awakening) may nevertheless influence sleep profiles in PTSD patients in a pervasive manner. In other words, we postulate that sleep disturbances in PTSD may be in part due to nightmare pathophysiology, rather than being exclusively attributable to PTSD-specific processes. Two studies conducted with individuals reporting fre- quent nightmares but who do not suffer from PTSD observed sleep disturbances comparable to those observed in PTSD patients, including increased or unaltered phasic REM sleep activity, decreased total sleep time, increased number and duration of nocturnal awakenings, and de- creased slow-wave sleep (Fisher et al 1970; Newell et al 1992). Another study (van der Kolk et al 1984) compared sleep complaints in nightmare sufferers with PTSD (n = 15) and individuals with idiopathic nightmares (n = 10). Posttraumatic stress disorder–related nightmares tended to occur earlier in the night, were more frequent, and were more often associated with gross body movements than were idiopathic nightmares; however, a lack of objective sleep measures obviates the possibility of determining more specifically whether these two groups had different types of sleep disturbances. Together, these observations suggest that the relationship between chronic frequent nightmares and sleep anomalies may not be exclusive to PTSD. Rather, these findings further support the notion From the Sleep Research Center (AG, TAN), Ho ˆpital du Sacre ´-Coeur de Montre ´al; and the Departments of Psychology (AG) and Psychiatry (TAN), Universite ´ de Montre ´al, Montre ´al, Que ´bec, Canada. Address reprint requests to Anne Germain, Ph.D., University of Pittsburgh School of Medicine, Department of Psychiatry, 3811 O’Hara Street, Suite E-1116, Pittsburgh PA 15213. Received January 17, 2002; revised July 10, 2002; revised November 27, 2002; accepted January 6, 2003. © 2003 Society of Biological Psychiatry 0006-3223/03/$30.00 doi:10.1016/S0006-3223(03)00071-4