Dhaka, Oct. 21 -- Scientists have identified a new subtype of depression tied to the body's internal clock, a finding that could explain why standard antidepressant treatments fail a significant number of patients and point the way towards more targeted therapies, The Independent reports.

The condition, termed "circadian depression", affects roughly one in four people among those with severe, recurrent or persistent depression, according to a study published in the British Journal of Psychiatry by researchers from the University of Sydney.

Circadian depression is characterised by a seasonal pattern of illness, sleeping longer during depressive episodes, waking feeling exhausted, and a tendency towards being a night owl. People with the ...