Background: The prevalence of comorbid insomnia is 8-10 times higher in patients with chronic pain than in the general population. Insomnia adds a considerable burden as it worsens the quality of life, restoration and repair, mental health and pain symptoms. Since pain and sleep problems are mutually reinforcing, improvements in sleep may have beneficial effects on pain. Unfortunately, the customary use of sleep medication (TAU: treatment-as-usual) often yields short-lived plus side effects. The Sleep-Well intervention examines if a group-based intervention program focusing on sleep literacy, sleep restriction, stimulus control and metacognitive therapy modules may perform better than TAU in improving patients' insomnia and sleep quality. Eligible patients: Investigators target adult patients referred to the University Hospital of North Norway (Tromsø) for a diagnostic evaluation of their pain condition. Patients eligible for the Sleep-Well study are those who satisfy diagnostic criteria for a non-malign pain disorder plus a comorbid insomnia sleep disorder. Patients are not eligible if they use drugs or large doses of morphine (\>100 equivalents), are engaged in an insurance case due to their diagnosis, or participate in other ongoing group programs at the hospital.

Aims: This trial uses a randomized semi-crossover design to examine if the Sleep-Well group does better regarding insomnia and sleep quality than the control patients (TAU). The primary outcome measures are reductions in diagnostic criteria for insomnia, self-reported insomnia symptoms, quality of life, and actigraphy-measured insomnia indicators (long sleep onset latency, frequent nightly awakenings and early morning awakening). The secondary outcome measures include a simplified polysomnography measurement of brain activity during sleep to assess if proportions or durations of slow-wave versus light-wave sleep and EEG-based arousal indices improve. In addition, it is examined if the Sleep-Well intervention incurs benefits concerning pain complaints, dysfunctional sleep and pain cognitions, anxiety and depression. The intervention: The Sleep-Well program schedules group sessions that cover four topics (sleep literacy, behavioural and mental strategies, maintenance and relapse prevention). All sessions are led by two therapists. Those randomized to the active control group (TAU) cross over to the Sleep-Well intervention three months later.