Researchers identify new subtype of depression linked to body clock

SYDNEY, Oct. 21 (Xinhua) -- Researchers in Australia have identified a subtype of depression linked to disruptions in the body's internal 24-hour clock that regulates the sleep-wake cycle, potentially paving the way for more targeted behavioral and medical treatments.

People dine at a cafe inside the Museum of Contemporary Art Australia (MCA) in Sydney, Australia, May 17, 2024. (File photo: Xinhua)

The study analyzed clinical and genetic data from more than 10,000 Australians with severe, recurrent or persistent depression, identifying nearly a quarter of participants as having what researchers termed "circadian depression," according to a statement released Wednesday by Australia's University of Sydney.

The subtype is characterized by symptoms including seasonal patterns of illness, longer sleep when depressed, waking feeling exhausted, and being a night owl, according to the study published in the British Journal of Psychiatry.

People with circadian depression were more likely to develop the illness earlier in life and had more severe symptoms, including higher levels of suicidal thoughts. They also had higher genetic risks for inflammatory and cardiovascular conditions and major neurodevelopmental disorders, including attention-deficit/hyperactivity disorder, the study showed.

Researchers said the subtype is more resistant to treatment by common serotonin-based antidepressants, but is more responsive to behavioral and medical therapies targeting the body clock's unique brain circuits, such as melatonin, melatonin-targeted antidepressants and light therapy.

The researchers warned that not recognizing circadian depression in young people often led to early treatment failures and more side effects.