Cognitive and psychological factors associated with treatment response in ACT-I and CBT-I for insomnia.

Cognitive behavioural therapy for insomnia is the treatment of choice for patients with insomnia, but not all patients benefit, and novel psychological treatment approaches have emerged (e.g. acceptance and commitment therapy). Thus, the aim of the present study was to evaluate whether treatment modality, adherence, insomnia severity, anxiety, depression, beliefs about sleep or acceptance of sleep problems are factors associated with response to psychological insomnia treatment. The sample consisted of 152 adults (115 women; mean age = 40.6 years, SD = 10.2) with chronic insomnia, and they participated in a randomized clinical trial comparing acceptance and commitment therapy for insomnia (as a standalone) with cognitive behavioural therapy for insomnia. The outcome measure was proportion of treatment responders (8 points reduction or more) on the Insomnia Severity Index, assessed at pre- and post-treatment and 6-month follow-up. The predictor variables were assessed at pre-treatment. The final multivariate model showed that undergoing cognitive behavioural therapy for insomnia increased the chances of treatment response at post-treatment by 2.70 times when compared with acceptance and commitment therapy for insomnia (odds ratio = 2.70 [1.14-6.38]). In addition, each additional point in pre-treatment insomnia severity (odds ratio = 1.15 [1.01-1.30]) and dysfunctional beliefs about sleep (odds ratio = 1.02 [1.00-1.05]) scores increased the chances of response at post-treatment. Treatment adherence increased the chances of treatment response at post-treatment by 3.07 times (odds ratio = 3.07 [1.28-7.34]). Finally, each additional point on the Insomnia Severity Index pre-treatment increased the chances of treatment response at the 6-month follow-up (odds ratio = 1.14 [1.01-1.29]). In conclusion, cognitive behavioural therapy for insomnia increases the chance of treatment response compared with acceptance and commitment therapy for insomnia. Moreover, higher adherence, insomnia severity and dysfunctional beliefs about sleep predict treatment outcome in both treatments.