Researchers Identify New 'Circadian' Subtype of Depression Affecting 1 in 4 Patients

Key Points:

• A new study led by University of Sydney researchers identified a "circadian" subtype of depression affecting about 25% of patients, characterized by symptoms linked to disruptions in the body's internal clock, similar to perpetual jet lag.
• This subtype features seasonal symptom changes, delayed sleep midpoint, social jet lag, evening chronotype, prolonged sleep when possible, and morning tiredness, distinguishing it from other forms of depression, including atypical depression.
• Individuals with circadian depression tend to experience earlier onset, more severe symptoms (mania, psychosis, suicidality), weight gain during episodes, and a higher genetic risk for neurodevelopmental and cardiovascular disorders.
• Patients with this subtype are less responsive to common antidepressants and report more side effects, suggesting that treatments targeting circadian rhythms, such as light therapy and melatonin, may be more effective.
• The findings emphasize the need to recognize depression as a heterogeneous disorder and to tailor treatments based on subtype, encouraging patients who do not respond to standard antidepressants to seek personalized clinical advice.