Outside experts warn that more research is needed before “circadian depression” can be classified as a subtype

October 22, 2026 2:15 p.m.

The researchers’ criteria for circadian depression includes morning sleepiness, delayed sleep timing, social jet lag, excessive sleeping during depressive episodes, and seasonality. Guido Mieth via Getty Images

One in four people with depression could have a newly identified subtype called “circadian depression” caused by a dysregulated body clock, suggests a new study.

The work, published in the British Journal of Psychiatry on October 21, deepens our understanding of depression and could lead to more effective intervention and treatment for people affected by this subtype.

“Depression is not a uniform illness, and understanding the characteristics of different subtypes means that we can give people earlier access to treatments that will be most effective for them,” says study co-author Emiliana Tonini to Lauren Roberts at the Australian Broadcasting Corporation…