Adaptation effects to sleep studies in participants with and without chronic posttraumatic stress disorder.

The "first night effect" (FNE) is the alteration of sleep architecture observed on the first night of polysomnographic (PSG) studies. It is unclear whether the FNE reflects adaptation to the equipment, sleeping environment, or both. Moreover, it is possible that certain patient populations, such as those with posttraumatic stress disorder (PTSD), demonstrate greater adaptation effects that are highly context dependent. We assessed FNE in participants with PTSD and healthy controls in a cross-sectional study consisting of PSG testing at home and in the hospital. Contrary to our expectations, the PTSD group showed no adaptation effects in either setting. Only the control group assigned to the "hospital first" condition showed significant decreases in total sleep time on night 1 versus night 2 of the study. The results suggest that the FNE is related to adaptation to the combination of the hospital environment and the recording equipment.