Researchers from the University of Sydney identified a 'circadian' subtype of depression affecting nearly a quarter of participants, linked to body clock disruptions and poor response to standard antidepressants.
By Hermes-Vector AI Desk
Researchers from the University of Sydney have identified a new subtype of depression linked to disruptions in the body’s internal clock. The study, published in the British Journal of Psychiatry, suggests that this "circadian depression" affects nearly a quarter of patients with severe or recurrent depression and may respond poorly to traditional antidepressant treatments.
The research team, led by psychiatry researchers Jacob Crouse and Ian Hickie, analyzed clinical and genetic data from 11,380 participants in the Australian Genetics of Depression Study. The study defined circadian depression by the presence of at least three of six specific features:
According to the study, 2,604 participants, or approximately 23% of the total, met these criteria. Dr. Emiliana Tonini, the study’s first author, stated that the researchers defined the condition based on these characteristics to identify a biologically valid phenotype.
Participants identified with the circadian subtype reported more severe clinical features compared to those without the subtype. These features included an earlier age of onset, more episodes, and higher rates of suicidality, mania, and psychotic-like symptoms. The group also reported more weight gain during depressive episodes.
The study found that individuals with circadian depression were less likely to find common antidepressant medications, such as SSRIs and SNRIs, effective. They also reported experiencing more side effects from these medications. Prof. Ian Hickie, co-director of the Brain and Mind Centre, noted that poor response to standard therapies is a critical feature of this type.
"Because circadian depression is linked to people's internal body clock, treatments targeting the circadian rhythm, such as light therapy and melatonin, may be much more relevant, and clinicians should reach for these much earlier in people with this presentation," Crouse said.
The researchers found that participants with the circadian subtype had a higher genetic risk for major neurodevelopmental disorders, including ADHD, as well as inflammatory and cardiovascular health problems. Tonini emphasized that this indicates the condition is "not just depression with bad sleep," but has an underlying biology distinct from other forms.
However, independent experts urged caution regarding the immediate clinical application of these findings. Prof. Andrew Coogan, a behavioral neuroscientist at Maynooth University, noted that the link between depression and body clock changes has been known for a long time. He described the results as "initial if interesting findings" and cited a lack of detail on how the specific criteria were chosen.
Brant Hasler, a sleep researcher at the University of Pittsburgh, pointed out that the study relied on participants' self-reports of their sleep, which correlate only modestly with direct physiological measures. Additionally, the study participants were limited to those of genetically inferred European ancestry, which may limit the generalizability of the results.
This research suggests that depression is not a uniform illness and that identifying specific subtypes could lead to more effective, tailored treatments. For patients who do not respond to standard antidepressants, targeting circadian rhythms through light therapy or melatonin may offer a more effective path to relief. However, experts agree that further research is needed to validate these findings in diverse populations before they change clinical practice.
Sources
This article was drafted with AI assistance and checked against the sources above. Company claims are reported as claims. Cover image is AI-generated.
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