An Australian study suggests that some people with depression may share a distinct form of the illness linked to their internal body clock. This system helps regulate the daily pattern of sleeping and waking. Researchers examined information from 11,380 adults in the Australian Genetics of Depression Study. They found that 2,604 participants—about one-quarter—matched their proposed “circadian depression” subtype.
Participants qualified if they had at least three of six features: seasonal mood changes, late sleep schedules, a preference for evenings, unusually long sleep, tiredness upon waking, or different sleep schedules on workdays and free days. In this group, depression began at around age 19, compared with about 23 among other participants. They also reported less improvement with common antidepressants, which are medicines for depression, and more side effects.
The researchers suggest that bright light therapy or melatonin, a hormone involved in sleep timing, might benefit this group. However, the subtype is not yet formally established, and clinical trials are needed to test possible treatments. Participants reported their own sleep habits, which do not necessarily show whether their internal clocks are disrupted. Further research is needed before these findings can guide treatment decisions. The study appeared in The British Journal of Psychiatry.
