Insomnia and hallucinations in the general population: Findings from the 2000 and 2007 British Psychiatric Morbidity Surveys.

Insomnia is common in people experiencing psychosis. It has been identified as a contributory cause of paranoia, but any causal relationship with hallucinations has yet to be established. We tested the hypotheses that insomnia i) has a cross-sectional association with hallucinations ii) predicts new inceptions of hallucinations and iii) that these associations remain after controlling for depression, anxiety, and paranoia. Data from the second (2000, N=8580) and third (2007, N=7403) British Psychiatric Morbidity Surveys were used to assess cross-sectional associations between insomnia and hallucinations. The 2000 dataset included an 18 month follow up of a subsample (N=2406) used to test whether insomnia predicted new inceptions of hallucinations. Insomnia was associated with hallucinations in both cross-sectional datasets. Mild sleep problems were associated with 2-3 times greater odds of reporting hallucinations, whilst chronic insomnia was associated with four times greater odds. Insomnia was also associated with increased odds of hallucinations occurring de novo over the next 18 months. These associations remained significant, although with smaller odds ratios, after controlling for depression, anxiety and paranoia. This is the first longitudinal evidence that insomnia is associated with the development of hallucinatory experiences. Effective treatment of insomnia may lessen the occurrence of hallucinations.