An online behavioural self-help intervention rapidly improves acute insomnia severity and subjective mood during the COVID-19 pandemic: a stratified randomised controlled trial.

An online behavioural self-help intervention rapidly reduces acute insomnia severity (within one week), and benefits mood in people with acute insomnia. These beneficial effects are maintained up to three months later. Although the use of the intervention is feasible in good sleepers, their subjective sleep was unaffected.