Insomnia Disorder is Associated with Increased Amygdala Reactivity to Insomnia-Related Stimuli

Study Objectives: Alterations in emotional reactivity may play a key role in the pathophysiology of insomnia disorder (ID). However, only few supporting experimental data are currently available. We evaluated in a hypothesis-driven design whether patients with ID present altered amygdala responses to emotional stimuli related and unrelated to the experience of insomnia and, because of chronic hyperarousal, less habituation of amygdala responses. Design: Case-control study. Setting: Departments of Psychiatry and Psychotherapy and of Radiology of the University of Freiburg Medical Center. Participants: There were 22 patients with ID (15 females; 7 males; age 40.7 ± 12.6 y) and 38 healthy good sleepers (HGS, 21 females; 17 males; age 39.6 ± 8.9 y). Interventions: N/A. Measurements and Results: In a functional magnetic resonance imaging session, five different blocks of pictures with varying emotional arousal, valence, and content (insomnia-relatedness) were presented. Pictures were presented twice to test for habituation processes. Results showed that patients with ID, compared to HGS, presented heightened amygdala responses to insomnia-related stimuli. Moreover, habituation of amygdala responses was observed only in HGS, but not in patients with ID who showed a mixed pattern of amygdala responses to the second presentation of the stimuli. Conclusions: The results provide evidence for an insomnia-related emotional bias in patients with insomnia disorder. Cognitive behavior treatment for the disorder could benefit from strategies dealing with the emotional charge associated with the disorder. Further studies should clarify the role of insomnia disorder with respect to habituation of amygdala responses.