Assessing a hyperarousal hypothesis of insomnia in adults with autism spectrum disorder

This study aimed to investigate the relationship between sleep, psychopathology (anxiety, depression and presleep arousal) symptoms, and cortisol in adults with autism spectrum disorder (ASD). The sample composed of 29 adults with ASD (51.7% males) and 29 control adults (51.7% males) aged 21-44 years. Thirteen adults with ASD were medicated for a comorbid diagnosis of anxiety and/or depression (ASD-Med), while the remaining 16 adults with ASD were not medicated for such diagnoses (ASD-Only). Participants completed a questionnaire battery, 14-day sleep/wake diary and 14-day actigraphy assessment. On one day during the data collection period, participants collected five saliva samples, hourly, prior to sleep and two morning samples; immediately upon waking and 30 min thereafter for the analysis of cortisol. Cortisol 1 hr prior to habitual sleep onset time was associated with poorer sleep efficiency in both ASD groups and increased wake after sleep onset duration (ASD-Only). Higher subjective somatic arousal was also associated with increased sleep onset latency, regardless of group, and poorer sleep efficiency in the ASD-Only group. ASD-Only participants had significantly greater reductions in evening cortisol concentrations compared to both ASD-Med and control participants. No significant group differences were found for the cortisol awakening response. Findings suggest a hyperarousal hypothesis of insomnia in adults with ASD. Moreover, the low cortisol levels observed in ASD-Only adults suggest dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis. Longitudinal studies exploring the interplay between insomnia, anxiety and HPA axis regulation across the lifespan in those with ASD are warranted. Autism Res 2019, 12: 897-910. © 2019 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: Both objective (cortisol) and subjective (somatic) physiological arousal were associated with poor sleep quality in adults on the autism spectrum. Adults with autism spectrum disorder (ASD) who were not medicated for a comorbid diagnosis of anxiety and/or depression also had dampened cortisol secretion, suggesting a dysregulation of the hypothalamic pituitary axis. Longitudinal studies investigating the relationship between sleep, psychopathology symptoms and physiological arousal in autistic individuals are warranted. Autism Res 2019. © 2019 International Society for Autism Research, Wiley Periodicals, Inc.