Effectiveness of group-delivered cognitive behavioural therapy for insomnia in primary care: a pragmatic, multicentre randomised controlled trial

Insomnia is a prevalent disorder in the general population. Group delivery increases access to the treatment of choice for insomnia, cognitive-behavioural therapy for insomnia (CBT-I). The aim of this pragmatic randomized controlled trial was to investigate the effectiveness of low-threshold group-delivered CBT-I implemented in Norwegian primary care. The trial was registered in the ISRCTN registry (ISRCTN16185698), and conducted across 26 Healthy Life Centres. Inclusion criteria were age ≥ 18 years and insomnia symptoms with a significant impact (Insomnia Severity Index (ISI) ≥ 12). Eligible participants were randomized to group-delivered CBT-I or to a waiting list according to a 2:1 ratio. The intervention consisted of four 2-h sessions over 4 weeks, with 5-15 participants per group. Primary outcome was self-reported insomnia severity at 3-months follow-up, measured by the ISI. Participants were not blinded to group assignment, but those responsible for analyses and interpretation of the results were. In total, 308 participants were randomly allocated to group-delivered CBT-I (n = 181) or waiting list (n = 127). The mean difference in ISI score between groups at 3-months follow-up was -3.4 (95 % CI: 4.3 to -2.5), favoring the group-delivered CBT-I. Of those receiving group-delivered CBT-I, 51 (33.6 %) reported a clinically relevant improvement in insomnia severity (i.e., ≥ 8 points on ISI), compared to 15 (13.2 %) on the waiting list (OR 3.4, 95 % CI: 1.7 to 6.8). Thus, group-delivered CBT-I reduced insomnia severity at 3-months follow-up for adults with insomnia. Group-delivered CBT-I offered at Healthy Life Centres is a suitable low-threshold treatment for insomnia in primary care.