The authors challenge the traditional view that sleep problems are merely a secondary consequence of psychosis, presenting evidence that disrupted sleep may contribute to the onset and persistence of symptoms such as paranoia and hallucinations. Insomnia and nightmare disorder were identified as particularly common among people experiencing psychosis, and longitudinal studies suggest that sleep difficulties can predict later psychotic experiences. Psychological interventions for sleep, particularly cognitive behavioural therapy for insomnia (CBT-I), were found to produce substantial improvements in sleep and may also reduce psychotic symptoms. Overall, the review positions sleep as a modifiable and clinically meaningful target that could improve both sleep quality and broader mental health outcomes in psychosis.