A new study from the University of Sydney's Brain and Mind Centre is getting a lot of attention this week.
The paper: Tonini et al. Clinical and genetic correlates of a circadian subtype of depression in the Australian Genetics of Depression Study. British Journal of Psychiatry, Oct 21 2026. DOI: 10.1192/bjp.2026.10798
What they did: Analyzed 11,380 adults with severe, recurrent depression from the Australian Genetics of Depression Study.
How they defined it: Need 3 of 6 features — seasonality, being a definite night owl, delayed sleep midpoint, 2+ hours social jet lag between work/free days, sleeping much more when depressed, and severe morning tiredness.
Result: 2,604 people, 23%, fit this "circadian depression" profile.
Why it matters:
Earlier onset, more episodes, more suicidality, more hypomanic and psychotic-like features
Worse response to SSRIs (OR 0.88) and SNRIs (OR 0.89) and more side effects
Distinct genetics: higher polygenic risk for ADHD, depression, anxiety, bipolar, plus BMI, triglycerides, IL-6, insulin resistance, and a strong genetic link to evening chronotype
The takeaway: For this group, disrupted clock may be driving the illness. Authors argue for circadian-focused care — consistent wake time 7 days/week, morning/midday/sunset outdoor light, regular meals/activity, plus clinical options like melatonin, light therapy, and melatonergic meds — rather than another round of SSRIs.
Don't stop antidepressants on your own. This is a provisional research subtype, now being tested in the MELODY trial.
References:
Original peer-reviewed paper (full text):
Tonini, E., Crouse, J.J., Shin, M., et al. Clinical and genetic correlates of a circadian subtype of depression in the Australian Genetics of Depression Study. British Journal of Psychiatry (2026).
https://www.cambridge.[STRIPPED 211 bytes]: https://doi.org/10.1192/bjp.2026.10798
University of Sydney official press release (Oct 21, 2026):
https://www.sydney.edu.au/news-opinion/news/2026/10/21/researchers-identify-circadian-subtype-of-depression-.html
MedicalXpress summary of the study:
https://medicalxpress.com/news/2026-10-circadian-subtype-depression.html
Smithsonian Magazine coverage with outside expert commentary:
https://www.smithsonianmag.com/smart-news/one-in-four-cases-of-depression-could-be-caused-by-a-dysregulated-body-clock-study-says-180989736/
Medical Republic detailed clinical summary with ORs and demographics:
https://www.medicalrepublic.com.au/depression-treatment-may-need-to-account-for-the-body-clock/130233