Genetic proximity to diurnal preferences, sleep timing, and risk of major depressive disorder.

Daghlas I, Lane JM, Saxena R, Vetter C. Genetically proximate diurnal preference, sleep timing, and risk of major depressive disorder. JAMA Psychiatry. published online May 26, 2021. doi:10.1001/jamapsychiatry.2021.0959

Morning diurnal 

preference has been associated with risk of major depressive disorder (MDD), but the causality of this association is unknown, so this study used Mendelian randomization to investigate the association between genetically proximate morning diurnal preference and risk of depression.

A total of 697,828 individuals were included in the UK Biobank and 23andMe cohorts, 85 502 biobanks in the UK had measurements of sleep midpoint, and 170,756 MDD patients and 329,443 control participants were included in the Psychiatric Genomics Consortium and UK Biobank data.

The results showed 

that genetically close early diurnal preference was associated with a 23% lower risk of depression. However, this is not statistically significant when defined by the UK Biobank hospital-based billing codes.

In conclusion, the results of this Mendelian randomized study support a protective association between risk of MDD and early diurnal preference, and provided contextualized estimates for objective sleep timing measures.