Study identifies circadian rhythm subtype of depression, questioning standard therapies

A large Australian study published in The British Journal of Psychiatry examined 11,380 adults diagnosed with depression and identified a distinct “circadian depression” subtype linked to misaligned body clocks. Approximately 25 % of participants and about one-third of younger patients met at least three of six criteria, including seasonal mood changes, extended sleep during depressive episodes, morning grogginess, night-owl tendencies, late waking, and social jet lag.

This subgroup exhibited a higher risk of bipolar disorder and ADHD, and standard interventions—selective serotonin reuptake inhibitors and cognitive-behavioral therapy—were found to be ineffective or possibly detrimental. Researchers emphasized the importance of light exposure, recommending bright daytime light, minimal nighttime light, and consistent sleep timing, while future trials will explore melatonin-based treatments. Experts note that addressing circadian disruption may be crucial for preventing relapse, especially among women, adolescents, and post-natal cases.