Australian researchers identify new subtype of depression linked to body clock disruptions

Australian researchers have identified a new subtype of depression, termed circadian depression, which is linked to disruptions in the body’s internal clock. This subtype is believed to be less responsive to traditional antidepressant treatments. The findings were published in the British Journal of Psychiatry and are based on clinical and genetic data from 11,380 Australians suffering from mostly severe and recurrent depression.

• Circadian depression affects nearly a quarter (23%) of the participants in the study.
• Researchers suggest that individuals with this subtype may benefit from treatments targeting the body’s circadian rhythms, such as melatonin and light therapy.

Dr. Emiliana Tonini, the study’s first author from the University of Sydney’s Brain and Mind Centre, defined circadian depression as occurring in participants who exhibited at least three out of six specific features:

• Experiencing a seasonal pattern of illness
• Delayed sleep timing
• Sleeping longer when depressed
• Identifying as a night owl
• Waking up feeling very tired
• Experiencing social jetlag

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“Individuals with circadian depression have more severe mental health symptoms,” Tonini stated during a press briefing. “The age of onset of their depression was younger compared to those with non-circadian depression, but they also had more episodes and more complex trajectories, including increased suicidality and hypomanic and psychotic-like symptoms.”