The recommended treatment for insomnia, cognitive behavioral therapy for insomnia (CBT-I), is effective. However, its long, multi-component nature makes it challenging to implement in ordinary primary care, where most people are treated. An important component of CBT-I is sleep restriction therapy, which may be comparatively easy to carry out in routine primary care. This project tests whether a brief nurse-led group intervention in primary care based on sleep restriction therapy for insomnia reduces insomnia severity and is cost-effective.

Background: Insomnia is typically treated in primary health care. The most common treatment is hypnotic drugs, despite their limited and short-term effects, the risk for adverse side effects and dependence, and the fact that CBT-I is the recommended first-line treatment. Reasons may include lack of knowledge about insomnia, a culture of prescribing hypnotics, lack of time during consultations, and a shortage of CBT-I providers. Sleep restriction therapy is one of the core components of CBT-I. It is a behavioral technique that may be feasible to deliver in routine care with existing resources and time constraints.

Objectives: This randomized controlled trial aims to investigate whether brief, behavioral group therapy in primary care based on sleep restriction therapy reduces insomnia severity and is cost-effective. A process evaluation will explore barriers and facilitators for participation and delivery.

Methods: Health care professionals from participating primary health care centers will complete a 1.5-day digital course on assessing patients for insomnia and delivering the intervention. Patients who seek primary health care and meet the study criteria will be randomized to sleep restriction therapy or to receive written sleep hygiene information. Both groups will be free to seek and receive standard care for insomnia. Sociodemographic and clinical characteristics will be collected prior to baseline. Study outcomes include insomnia severity, sleep, daytime symptoms, quality of life, use of hypnotics, sick leave, and work ability. Outcomes will be assessed over a 24-month period. The cost-effectiveness analysis will include the number of insomnia-free days at the 12-month follow-up and quality-adjusted life years. Patient characteristics will be analyzed in relation to adherence, and response. Qualitative explorations of patients and nurses' experiences will be conducted alongside the trial (approximately 15 patients and 15 nurses).

Inclusion Criteria:

• Fulfills the DSM-5 diagnostic criteria for insomnia disorder: a) Difficulty initiating sleep, difficulty maintaining sleep, and early morning awakenings despite adequate opportunity for sleep (e.g., adequate time and circumstances for sleep and a safe, quiet, and dark bedroom). b) The sleep difficulties cause significant distress or impairment in social, occupational, educational, academic, behavioral, or other important areas of functioning. c) The sleep difficulties occur at least 3 nights per week and have been present for at least 3 months. d) The symptoms are not better explained by and do not occur exclusively during the course of another sleep-wake disorder. e) The symptoms cannot be attributed to the effects of a substance (e.g., drug abuse and medication). f) Coexisting mental disorders and medical conditions do not adequately explain the predominant complaint of insomnia.

Exclusion Criteria:

• Severe psychiatric illness (e.g., severe depression, schizophrenia, bipolar disorder)
• Suicidal ideation
• Untreated sleep disorder other than insomnia (e.g., sleep apnea, and restless legs syndrome)
• Epilepsy
• Cognitive disorder
• Pregnancy
• Night shift work
• Language difficulties (inability to understand and speak Swedish well enough to participate in the intervention and respond to measurement instruments)
• ≤ 7 points on the Insomnia Severity Index

Study staff entering data will be blinded to the condition. The researchers will provide some supervision to the health care professional who deliver the treatment. The researchers will therefore know the identities of the health care professionals they supervise. However, outcome data will be pseudonymized, so researchers will be blinded during outcome assessment. It is not possible to blind the health care professionals delivering the treatment or patients receiving it.