Researchers identify a subtype of depression associated with biological clock dysregulation

Researchers in Australia have identified a subtype of depression associated with the disruption of the circadian rhythm-the approximately 24-hour biological mechanism that regulates the sleep-wake cycle. This discovery could pave the way for more targeted behavioral and medical treatments, according to the news agency Xinhua.

The study analyzed clinical and genetic data from over 10,000 Australians suffering from severe, recurrent, or persistent depression. Nearly a quarter of the participants exhibited characteristics of a form that researchers have termed "circadian depression," according to a statement released by the University of Sydney. The research findings were published in the British Journal of Psychiatry.

• Prolonged sleep, exhaustion upon waking, and more severe symptoms

Circadian depression is characterized by a set of symptoms linked to the biological rhythm. These include the seasonal manifestation of depression, longer sleep duration during periods when symptoms occur, a feeling of exhaustion upon waking, and a tendency to stay awake late into the night. According to the researchers, individuals with this profile are more likely to develop depression at a younger age and tend to experience more severe symptoms, including a higher level of suicidal thoughts. The study also identified higher genetic risks for certain inflammatory and cardiovascular conditions, as well as for neurodevelopmental disorders, including attention-deficit/hyperactivity disorder (ADHD).

• Potential treatments tailored to biological rhythms

Another significant finding of the research is that "circadian depression" may respond differently to available treatments. According to the study's authors, this subtype appears more resistant to conventional antidepressants that act on serotonin. Conversely, researchers observed a better response to interventions targeting brain circuits involved in regulating the biological clock. These include melatonin, medications that act on the melatoninergic system, and light therapy. These findings could contribute to a more personalized approach to treating depression by identifying individuals for whom circadian rhythm dysregulation is a key component of their condition. While the research describes a subtype associated with specific clinical and genetic characteristics, its identification does not mean that everyone who sleeps a lot, wakes up feeling tired, or prefers to stay awake at night necessarily suffers from circadian depression.