This two-arm randomized trial will provide digital cognitive behavioral therapy for insomnia (CBT-I) to all participants and passive body heating (PBH) sessions using a sauna blanket to half of participants over a 9-week treatment period. Participants are adults aged 18 years or older with insomnia disorder.
Insomnia disorder is a common and consequential mental health problem, with prevalence estimates at approximately 10%. The American College of Physicians recommends cognitive behavioral therapy for insomnia (CBT-I), an efficacious "mind" (psychological and behavioral) treatment, as the first-line treatment for adults with insomnia. Yet, about half of individuals experience residual insomnia symptoms after CBT-I. Accordingly, researchers have sought to augment CBT-I, primarily with pharmacotherapy, but many people do not want to use pharmacologic agents due to concerns about side effects and dependence. Passive-body heating (PBH), a "body" treatment, involves heating the body via hot baths or showers, infrared sauna, or other heat sources. PBH has been found to reduce the time needed to fall asleep and to improve sleep quality. PBH may improve sleep by increasing skin temperature and decreasing core body temperature, a dynamic associated with sleep onset. CBT-I and PBH thus target distinct factors that may contribute to insomnia, and the investigators hypothesize that the combination of CBT-I and PBH holds promise as a multi-component treatment for insomnia disorder.