Abstract
OBJECTIVES: Abnormalities in the stress system have been implicated in insomnia. However, studies examining physiological stress regulation in insomnia have not consistently detected differences in the hypothalamic-pituitary-adrenal (HPA)-axis response to stress. One explanation may be that deficits in the stress system are associated specifically with a biological vulnerability to insomnia rather than the phenotypic expression of insomnia. To examine stress response as a function of vulnerability to insomnia, this study tested response to the Trier Social Stress Test in a sample of healthy sleepers with varying familial risks for insomnia. METHODS: Thirty-five healthy individuals with and without familial risk for insomnia were recruited to complete a laboratory stressor. Participants with one or both biological parents with insomnia were categorized as positive for familial risk, whereas those without biological parents with insomnia were categorized as negative for familial risk. Participants completed the Trier Social Stress Test in the laboratory, and psychological and physiological (autonomic and HPA-axis) responses were compared. RESULTS: Despite self-reported increases in anxiety, those positive for familial risk exhibited a blunted cortisol response relative to those without familial risk for insomnia. Individuals with blunted cortisol also reported heightened reactivity to personal life stressors, including increased sleep disturbances, elevated cognitive intrusions, and more behavioral avoidance. CONCLUSIONS: Findings from this study provide initial evidence that abnormal stress regulation may be a biological predisposing factor conferred via familial risk for insomnia. This deficit may also predict negative consequences over time, including insomnia and the associated psychiatric comorbidities.