Researchers Identify a Possible Circadian Subtype of Depression

Depression can affect mood, motivation, concentration, sleep and daily functioning. However, the condition does not present identically in every person. Some people experience major disruptions to their sleep-wake cycle, including sleeping longer than usual, waking unrefreshed or having a strong tendency to stay awake late at night.

Researchers from the University of Sydney examined clinical and genetic data from the Australian Genetics of Depression Study. They identified a group whose symptoms appeared more closely linked to circadian rhythms—the internal biological processes that regulate sleep and wakefulness over roughly 24 hours.

The researchers suggested that recognising such patterns could help clinicians study whether treatments targeting sleep timing and circadian regulation may be useful for some patients. Approaches under investigation include structured behavioural interventions, light therapy and treatments affecting melatonin pathways.

The findings do not mean that circadian depression is already a universally accepted diagnostic category, or that the same treatment will work for everyone in the group. Independent replication and clinical trials are needed to establish how best to use this information.

People experiencing persistent depression should seek professional assessment. They should not start light therapy or change antidepressant medication without appropriate clinical advice.