A bidirectional Mendelian randomization (MR) study published in BMC Psychiatry found that daytime napping may be a predictor and potential intervention strategy for progression and treatment of schizophrenia.
Investigators from Wenzhou Medical University in China sourced data for this study from the United Kingdom (UK) Biobank (n=452,633), 23andMe (n=541,333), and the Psychiatric Genomics Consortium (PGC) (cases: n=36,989; controls: n=113,075) datasets. The significant single nucleotide polymorphisms (SNPs) that were replicated and associated with daytime napping frequency were related with the significant and replicated SNPs that associated with schizophrenia from the UK Biobank and 23andme datasets were compared with SNPs that associated with schizophrenia in the PGC dataset. Napping was defined as “never or rarely,” “sometimes,” or “usually.”
After MR analysis, 64 of the daytime napping SNPs had a causal relationship with schizophrenia (odds ratio [OR] range, 3.30-4.50). After removing outliers, 47 SNPs remained significant (OR range, 3.37-3.55).
Similarly, 77 of the schizophrenia SNPs had a causal relationship with daytime napping frequency (β range, 0.0090-0.0106). After removing outliers, 51 remained significant (β range, 0.0112-0.0115).
Overall, there was no evidence of horizontal pleiotropy for either the effect of napping on schizophrenia (P =.27) or schizophrenia on napping (P =.68).
These findings indicated there was a bidirectional relationship between napping and schizophrenia, in which for every 1-unit increase in napping frequency, risk for schizophrenia increased (P =3.58×10-6) and that the occurrence of schizophrenia increased with the frequency of daytime napping (P =2.04×10-5).
This study may have been limited, as napping was quantified as a binary exposure. More frequent napping and specific napping durations were not accounted for in this analysis. Additional study is needed to better-quantify napping characteristics.
Study authors concluded, “The findings of this bidirectional 2-sample Mendelian randomization study suggested a bidirectional causal association between more frequent daytime napping the occurrence of schizophrenia, implying that daytime napping frequency is a potential intervention for the progression and treatment of schizophrenia.”
Ma J, Jin C, Yang Y, Li H, Wang Y. Association of daytime napping frequency and schizophrenia: a bidirectional two‑sample Mendelian randomization study. BMC Psychiatry. 2022;22(1):786. doi:10.1186/s12888-022-04431-y