Faculty Bibliography

OBJECTIVE: Memory for odors is often associated with highly emotional experiences, and odors have long been noted by clinicians to be precipitants of trauma symptoms in posttraumatic stress disorder (PTSD). Primitive brain systems involved in fear responsivity and survival also mediate smell, including the olfactory cortex and amygdala. The purpose of this study was to measure neural correlates of olfaction in PTSD. METHODS: We exposed male combat veterans with PTSD (N = 8) and without PTSD (N = 8) to a set of smells, including diesel (related to traumatic memories of combat), and three other types of smells: odorless air, vanilla/coconut, and hydrogen sulfide (H2S) (respectively, a neutral, positive, and negative hedonic nontraumatic smell) in conjunction with PET imaging of cerebral blood flow and assessment of psychophysiological and behavioral symptoms. All subjects also underwent a baseline of olfactory acuity. RESULTS: PTSD patients rated diesel as unpleasant and distressing, resulting in increased PTSD symptoms and anxiety in PTSD versus combat controls. Exposure to diesel resulted in an increase in regional blood flow (rCBF) in amygdala, insula, medial prefrontal cortex, and anterior cingulate cortex, and decreased rCBF in lateral prefrontal cortex in PTSD in comparison to combat controls. Combat controls showed less rCBF changes on any smell, and did not show amygdala activation upon diesel exposure. CONCLUSIONS: These data support the hypothesis that in PTSD trauma-related smells can serve as strong emotional reminders. The findings indicate the involvement of a neural circuitry that shares olfactory elements and memory processing regions when exposed to trauma-related stimuli.

BACKGROUND: Nightmares and insomnia are experienced by 70% of patients suffering from post-traumatic stress disorder (PTSD). These sleep problems are often resistant to treatment and exert a strong negative influence on the quality of life. In the last few decades several studies have reported on the characteristics of sleep disturbances in PTSD. AIM: To provide an overview of objective features of sleep disturbances - as opposed to self-report methods - in patients with PTSD. METHOD: Articles on this topic, published in peer-reviewed journals between 1980 and the present, were retrieved from Medline and Embase, using the search terms 'PTSD', 'sleep', 'nightmares', 'insomnia', 'polysomnography'. RESULTS: Studies reported on changes in sleep efficiency, arousal regulation, motor activity during sleep, rem characteristics and delta sleep activity during sleep. Also, correlations were found between nightmares and sleep apnoea in ptsd. In some studies on sleep disturbance no objective sleep disturbances were found in PTSD patients. However, most studies on PTSD related sleep disturbances were conducted in small, heterogeneous groups, and results were therefore inconsistent. Even the results of larger and more homogeneous studies were sometimes contradictory. CONCLUSION: There is a discrepancy between the clinical importance of sleep problems in PTSD and unambiguous objective sleep disorders. Future research should try to establish objective criteria for identifying the altered sleep patterns in PTSD. These criteria should help us to understand the neurobiological mechanisms of sleep disturbances in PTSD and develop new treatment strategies.