Researchers at the University of Sydney have proposed a form of depression linked to the body's internal clock, which helps regulate sleep and waking. Using information from 11,380 adults in the Australian Genetics of Depression Study, they identified 2,604 people who fitted this proposed subtype: roughly one in four participants.
The group had at least three of six features: seasonal mood changes, late sleep times, a preference for evenings, different sleep schedules on working and free days, unusually long sleep, and tiredness on waking. Their depression began at around 19 on average, compared with about 23 among other participants. They also reported less benefit from common antidepressants, medicines used to treat depression, and more side effects.
The findings, published in the British Journal of Psychiatry, suggest that treatments targeting the sleep–wake system might help this group. Possible options include bright light therapy and melatonin, a hormone involved in sleep. However, clinical trials are needed before researchers can draw firm conclusions about treatment. The subtype is not yet formally established. Participants reported their own sleep patterns, and these reports do not necessarily show that their internal clocks are disrupted. Further research must also test whether the findings apply to wider populations.
