Sleep is essential for survival but a significant minority of the adult population are dissatisfied with their sleep, and 6-10% meet the criteria for insomnia disorder, characterised by difficulties falling asleep at bedtime, waking up in the middle of the night or too early in the morning, and daytime symptoms. Cognitive behavioural therapy for insomnia (CBT-I), an evidence-based sleep-focused intervention, has been suggested as the treatment of choice for chronic insomnia. However, access to specialised sleep therapists is sparse, and a service delivery model based on the principles of ‘stepped care’ has been proposed. Even though CBT-I is shown to be effective, there is a need to continue the development of cognitive behavioural treatments for insomnia. As a complement to traditional interventions, the potential value of acceptance, that is, to make an active choice of openness towards psychological experiences, has been recognized. However, it has not yet been systematically investigated, and specific instruments for studying acceptance in insomnia are lacking.

The present thesis is based on three studies: Study I showed that manual-guided CBT for insomnia delivered by ordinary primary care personnel has a significant effect on perceived insomnia severity, sleep onset latency and wake time after sleep onset. Study II demonstrated that non-responders in Study I reported shorter sleep time at baseline than did responders, a notion that may help select patients for this type of low-end intervention in a stepped care treatment approach. Study III aimed to develop a new assessment instrument for studying acceptance of insomnia, the Sleep Problem Acceptance Questionnaire (SPAQ), resulting in an eight-item questionnaire with two factors; the first being Activity Engagement, persisting with normal activities even when sleep is unsatisfactory, and the second involving Willingness, avoiding fighting and trying to control sleep problems.

In conclusion, the present thesis demonstrates that it is feasible to treat patients with insomnia using CBT-I administrated by ordinary primary care personnel in general practice, and that those with relatively longer initial sleep duration benefit most from treatment, enabling allocation to relevant treatment intensity. In addition, acceptance of sleep difficulties may be quantified using the SPAQ.