Insomnia is a major public health concern. While cognitive behavior therapy for insomnia (CBT-I) is acknowledged as the best available intervention, there are unanswered questions about its wider dissemination, socio-economic benefits and its impact on health resource utilization. The aim of this randomized controlled trial (RCT) is to investigate the effectiveness of a fully automated online version of CBT-I compared with online patient education about sleep (PE). Outcome measures comprise changes in symptoms of insomnia, time off work due to sick leave, as well as medication and health resource utilization. Also, we will examine putative mediators and selected potential psycho-bio-social moderators of the effects of the intervention.
Inclusion criteria: * Individuals aged \>=18 years who score \>= 12 on the Insomnia Severity Index (a score indicative of insomnia symptoms that significantly impact on individuals) * Willing and able to give online informed consent. Exclusion criteria: * Individuals scoring \>10 on the Epworth Sleepiness Scale (ESS) (which is suggestive of excessive daytime sleepiness) and/or answering that they usually or every day snore and stop breathing and have difficulties staying awake during the day (i.e., they positively endorse pre-selected indicators of sleep apnoea); * Self-report of the presence of any medical conditions where a fully automated CBT-I may be contra-indicated (e.g. epilepsy, bipolar disorder, schizophrenia or psychotic disorders, and recent heart surgery) * Participating in shift work.