Post-traumatic stress disorder and sleep-what a nightmare!

According to DSM IV criteria, sleep disturbances are incorporated in the definition of post-traumatic stress disorder (PTSD). These include the re-experiencing symptoms (nightmares, criteria B) and a hyperarousal state (difficulty initiating and maintaining sleep, criteria D). PTSD patients commonly complain of sleep disturbances. Moreover, insomnia, restless sleep and trauma-related dreams might be the primary complaint of some patients. However, although subjective sleep disturbances are considered characteristic of PTSD, sleep laboratory studies have provided inconsistent evidence of objective sleep disorders. A variety of sleep architectures and sleep patterns has been reported in PTSD. However, only a few studies have controlled for comorbidities. Thus, uncertainty exists to what extent the sustained complaints of sleep disturbances in chronic PTSD are specifically related to the impact of exposure to traumatic stress, or rather are a consequence of comorbid disorders. Specific changes in REM sleep suggest a pathophysiologic role of REM sleep abnormality in PTSD (e.g. anxiety dreams, increased REM density, exaggerated startle response, decreased dream recall and elevated awakening thresholds from REM sleep). However, again, studies have failed to show consistent changes in percentage of REM sleep or in REM latency. There might be a coexistence of pressure to REM along with inhibitory forces of REM that result in high variability of REM parameters across patients. Alternatively, changes in REM sleep might reflect the effect of comorbid psychiatric disorders that results in inconsistent findings between patients. The current review tries to address these issues based on recent studies carried out in this field.