Insomnia is a common and chronic disorder, and cognitive behavioral therapy (CBT) is the recommended treatment. Very long-term follow-ups of CBT are very rare, and this study aimed to investigate if improvements were stable one and ten years after CBT for insomnia (CBT-i). Based on a three-armed randomized controlled trial of bibliotherapeutic CBT-i, participants received an insomnia-specific self-help book and were randomized to therapist guidance, no guidance, or a waitlist receiving unguided treatment after a delay. Six weeks of treatment was given to 133 participants diagnosed with insomnia disorder. After one and ten years, participants were assessed with self-reports and interviews. Improvements were statistically significant and well maintained at one- and ten-year follow-ups. Average Insomnia Severity Index score [95%CI] was 18.3 [17.7-18.8] at baseline, 10.1 [9.3-10.9] at post-treatment, 9.2 [8.4-10.0] at one- and 10.7 [9.6-11.8] at ten-year follow-up, and 64% and 66% of participants no longer fulfilled criteria for an insomnia diagnosis at one and ten years, respectively. Positive effects of CBT were still present after ten years. Insomnia severity remained low, and two-thirds of participants no longer fulfilled criteria for an insomnia diagnosis. This extends previous findings of CBT, further confirming it as the treatment of choice for insomnia.
Keywords: CBT; Insomnia; treatment effects; very long-term follow-up.