Cogito, ergo insomnis : I think, therefore I am sleepless

Insomnia is a common health complaint that often becomes a persistent problem. The theoretical frameworks for understanding and treating insomnia have mostly been behavioural, yet the importance of cognitive processes has received greater attention over the years. The overall aim of this dissertation was to expand the knowledge on the processes from the Cognitive Model of Insomnia by investigating them in novel contexts. Study I examined the outcomes from cognitive therapy for insomnia on adolescents. Study II explored the relationship between cognitive processes and the association with remission and persistence of insomnia in the general population. Lastly, Study III investigated if cognitive processes mediated between cognitive behavioural therapy for insomnia (CBT-I) and outcomes of insomnia and depressive severity in a sample of people with insomnia comorbid with depressive problems. The findings show that cognitive therapy for insomnia affected sleep for adolescents, thus this is a promising treatment option for this age group. Further, it was found that cognitive processes distinguished between adults with normal sleep and persistent insomnia. For people with insomnia, elevated sleep-related worry at baseline increased the risk of reporting persistent insomnia later on, whereas a lowering of selective attention and monitoring, and safety behaviours over time increased the likelihood of remission from insomnia. This has clinical implications for insomnia assessment and treatment, as well as theoretical implications, and warrants further research. CBT-I was associated with greater reductions in dysfunctional beliefs and sleep-related safety behaviours compared to control treatment. Dysfunctional beliefs mediated between CBT-I and insomnia severity and depressive severity respectively. This supports the importance of negative thought content in both insomnia and depression