Early risers may have a lower risk of major depressive disorder (MDD) compared with night owls, according to a study published in JAMA Psychiatry.

Observational and interventional studies have shown the connection between early sleep timing and MDD protective factor. The reason for the connection, however, remains uncertain.

The study researchers conducted 2-sample mendelian randomization study, which used randomly allocated genetic variants associated with risk factor to test for causal effects on disease outcomes.


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The study used results from the first stage to scale estimates to represent a change in preference to a sleep cycle of about an hour later. The first stage examined the association of earlier diurnal preference with sleep midpoint, which is a behavioral marker for diurnal preference. The second stage tested the association or earlier sleep preference with MDD risk.

The primary analysis included 170,756 individuals with MDD and 329,443 control participants.

The researchers found that “genetically proxied morning diurnal preference corresponding to a 1-hour earlier sleep midpoint was associated with a 23% lower risk of MDD.” Results were “consistent across sensitivity analyses,” they reported.

The researchers acknowledged several gaps in their analysis. Most of the data came from observational studies. Also, MDD alters sleep and circadian rhythms, which may have skewed results. The study also does not adequately factor in extreme early- or late-risers. However, the researchers believe that their findings warrant larger clinical trials to further explore the issue.

Disclosure: One of study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures. 

Reference

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