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SYDNEY: Researchers in Australia have identified a subtype of depression associated with disruptions to the body’s internal 24-hour clock, a discovery that could pave the way for more targeted behavioural and medical treatments.
The study analysed clinical and genetic data from more than 10,000 Australians with severe, recurrent or persistent depression. Nearly a quarter of the participants were found to have what researchers described as “circadian depression”, according to a statement released by the University of Sydney on Wednesday.
Published in the British Journal of Psychiatry, the study identified a pattern of symptoms associated with the body’s circadian rhythm, which regulates the sleep-wake cycle and influences various biological processes.
People with this subtype were more likely to experience seasonal patterns in their illness, sleep longer during depressive episodes, wake up feeling exhausted and identify as night owls.
The researchers also found that people with circadian depression tended to develop the condition earlier in life and experience more severe symptoms, including higher levels of suicidal thoughts.
The study further linked the subtype to increased genetic risks for inflammatory and cardiovascular conditions, as well as major neurodevelopmental disorders, including attention-deficit/hyperactivity disorder (ADHD).
The findings suggest that disruptions to the body’s internal clock may play an important role in the development and severity of depression in a substantial group of patients.
According to the researchers, circadian depression may also respond differently to treatment than other forms of the condition. Patients with this subtype appeared more resistant to commonly prescribed serotonin-based antidepressants, while potentially benefiting more from treatments that target the brain circuits involved in regulating the body clock.
Such approaches include light therapy, melatonin and certain antidepressants that act on melatonin-related pathways. These treatments aim to help regulate circadian rhythms and improve the alignment between the body’s internal clock and daily sleep-wake patterns.
The researchers warned that failure to recognise circadian depression, particularly in young people, could contribute to unsuccessful early treatment and unnecessary side effects.
Identifying the subtype could help clinicians better understand why some patients do not respond well to standard antidepressants and guide decisions about alternative or complementary therapies.
However, further research will be needed to establish how the findings can best be translated into routine clinical practice and to determine which treatments are most effective for individual patients.
The study highlights the potential importance of sleep patterns and circadian rhythms in understanding depression, while underscoring the need for more personalised approaches to diagnosis and treatment.