A Mendelian randomization study found that some sleep traits, including duration, were associated with a diagnosis of schizophrenia.
The sleep traits studied were morning diurnal preference, sleep duration, daytime sleepiness, daytime napping, and insomnia, and the researchers chose these through meta-analyses of genome-wide association studies using data from the UK Biobank.
Analysis of 446,118 European ancestry participants revealed 78 loci for self-reported habitual sleep duration, 27 genetic loci for short sleep duration (less than 7 hours), and long sleep duration (at least 9 hours). In addition, 123 distinct genetic loci were identified for daytime napping; 42 for daytime sleepiness in 452,071; and 57 for self-reported insomnia.
Genetically predicted morning diurnal preference was associated with a lower risk of schizophrenia (odds ratio [OR], 0.839; 95% CI, 0.777-0.907), while genetically predicted sleep duration (OR, 1.562; 95% CI, 1.311-1.861) and daytime napping (OR, 2.051; 95% CI, 1.590-2.647) were associated with higher risks of schizophrenia.
Traits not associated with a higher risk of schizophrenia were insomnia (OR, 0.776; 95% CI, 0.550-1.096) and daytime sleepiness (OR, 1.766; 95% CI, 1.055-2.957).
Long sleep duration (OR, 1.404; 95% CI, 1.190-1.656) was associated with a higher risk of schizophrenia but short sleep duration was not (OR, 1.046; 95% CI, 0.908-1.206). The multivariable Mendelian randomization demonstrated an association with a higher risk of schizophrenia.
Genetically predicted schizophrenia had a negative association with morning diurnal preference (OR, 0.984; 95% CI, 0.977-0.992). An association between increased sleep duration (OR, 1.026; 95% CI, 1.020-1.032) and genetically predicted schizophrenia was found. Schizophrenia was not associated with daytime sleepiness (OR, 1.001; 95% CI, 0.998-1.004) or insomnia (OR, 1.002; 95% CI, 0.998-1.005).
There were some limitations to this study. There was a lack of non-European ancestry samples in the UK Biobank samples, which may have biased the results; there have been more risk loci for schizophrenia that have been identified since 2014 but were not included in this study; and participants with schizophrenia and who were on psychiatric medication were not excluded because of consistent effect estimates.
The researchers concluded that their study demonstrated an association between sleep traits and schizophrenia. These sleep traits can act as a treatment target for patients with schizophrenia.
Wang Z, Chen M, Wei YZ, et al. The causal relationship between sleep traits and the risk of schizophrenia: a two-sample bidirectional Mendelian randomization study. BMC Psychiatry. Published online April 25, 2022. doi:10.1186/s12888-022-03946-8