A study published in The British Journal of Psychiatry proposes a depression subtype associated with disruption of the body's circadian system, which regulates daily sleep-wake rhythms. University of Sydney researchers analyzed 11,380 adults participating in the Australian Genetics of Depression Study and identified 2,604 who met their proposed criteria. The findings suggest that approximately one-quarter of this cohort could fit the “circadian depression” category, an idea first proposed in 2021.
Classification required at least three of six features: seasonal mood variation, delayed sleep schedules, evening preference, excessive sleep, fatigue upon waking, and discrepancies between workday and free-day sleep schedules, known as social jet lag. Depression began at approximately age 19 in this group, versus 23 among other participants. Those meeting the criteria also reported greater psychological distress, less benefit from common antidepressants, and more adverse effects. Genetic analysis indicated elevated risk for several conditions, including depression, anxiety, ADHD, and bipolar disorder, as well as traits related to sleep and metabolism.
Researchers suggest that approaches targeting sleep-wake timing, including bright light therapy and melatonin, may warrant investigation. However, the subtype remains provisional, and clinical trials are necessary before treatment conclusions can be drawn. Independent sleep researcher Brant Hasler cautioned that self-reported sleep patterns do not establish physiological circadian disruption. Greater illness severity and additional psychiatric conditions could also contribute to poorer medication response. The findings require validation beyond this Australian cohort; notably, the genetic analysis included only participants of European ancestry.
