New Depression Subtype May Require Different Treatment, Study Suggests

A recently identified subtype of depression, termed 'circadian depression,' may explain why a significant portion of patients do not respond to conventional antidepressant medications, according to Australian researchers. This subtype is characterized by disrupted sleep and wakefulness patterns, potentially affecting up to a quarter of individuals experiencing depression.

The findings, published in the British Journal of Psychiatry and based on data from over 11,000 participants in the Australian Genetics of Depression Study, identified nearly 25 percent as having circadian depression. This condition is marked by seasonal illness patterns, excessive sleep, persistent fatigue, and a tendency to be more active at night. Researchers also noted that individuals with this subtype were more prone to developing depression at a younger age, experiencing more severe symptoms including mania and suicidal thoughts.

Genetic analysis further suggested an increased risk of heart disease, inflammatory conditions, and neurodevelopmental disorders like ADHD among those with circadian depression. The study's lead author, Dr. Emiliana Tonini from the University of Sydney, stated that understanding different subtypes of depression is crucial for providing patients with earlier access to the most effective treatments.

Scientists involved in the study propose that treatments targeting the circadian rhythm, such as light therapy and melatonin, could be more beneficial for patients with circadian depression. Dr. Jacob Crouse, a co-author, emphasized that for individuals who find antidepressants ineffective, discussing alternative options with a clinician is important. Professor Ian Hickie, a clinical psychiatrist at Sydney University's Brain and Mind Centre, highlighted the importance of recognizing this subtype in young people, suggesting that circadian-focused medical and behavioral options might be more effective than standard SSRIs for at least a quarter of them.

Melatonin, a hormone that regulates sleep-wake cycles, and light therapy are suggested as potential treatments to restore disrupted sleep patterns. However, some experts remain cautious. Professor David Curtis, an expert in genetics at University College London, questioned whether the findings constitute a new subtype, noting that many typical depression symptoms, like morning worsening of mood, are already circadian in nature. Other researchers acknowledged that while the findings may not immediately alter prescribing practices, they underscore the significance of assessing sleep-wake patterns in mood disorders.