RESEARCH ARTICLE Physiological Markers of Arousal Change with Psychological Treatment for Insomnia: A Preliminary Investigation

Objectives The aim of this preliminary study was to evaluate if Sleep Restriction Therapy for insomnia is associated with modifications to physiological arousal, indexed through overnight mea-sures of plasma cortisol concentrations and core body temperature. Methods In a pre-to-post open label study design, eleven patients with chronic and severe Psycho-physiological Insomnia underwent 5 weeks of Sleep Restriction Therapy. Results Eight (73%) patients out of 11 consented completed therapy and showed a decrease in insomnia severity pre-to-post treatment (mean (SD): 18.1 (2.8) versus 8.4 (4.8); p =.001). Six patients were analyzed with pre-to-post overnight measures of temperature and cortisol. Contrary to our hypothesis, significantly higher levels of plasma cortisol concentrations were found during the early morning at post-treatment compared to baseline (p <.01), while no change was observed in the pre-sleep phase or early part of the night. Core body tem-perature during sleep was however reduced significantly (overall mean [95 % CI]: 36.54 (°C) [36.3, 36.8] versus 36.45 [36.2, 36.7]; p <.05). Conclusions Sleep Restriction Therapy therefore was associated with increased early morning cortisol concentrations and decreased core body temperature, supporting the premise of physiolog-ical changes in functioning after effective therapy. Future work should evaluate change in physiological variables associated with clinical treatment response