Late to bed, late to rise, and still tired: a quarter of 11,000 fit the pattern

The clocks went back in Europe last Sunday, and the evenings have turned dark. A good week, then, for a study about the body clock and mood, and a good week to read it slowly.

The claim. Researchers at the University of Sydney’s Brain and Mind Centre, writing in the British Journal of Psychiatry, propose that some people have “circadian” depression, in which a disrupted body clock is a core feature, National Geographic reported on Friday¹. Their test is six self-reported traits: seasonal mood swings, late sleep, being a night owl, oversleeping, waking up very tired, and “social jet lag”, the gap between weekday and weekend sleep. Anyone with at least three counts¹. Of a cohort of more than 11,000 people, about a quarter fitted¹. Their depression tended to start earlier and to be more severe, and they were more likely to say antidepressants had not worked well¹.

The caveats, from the people themselves. The traits were self-reported, with no wearable data or melatonin measurements to confirm a disrupted clock¹. Co-author Jacob Crouse concedes the poor response to drugs might have other causes¹. David Curtis of the UCL Genetics Institute says the checklist may simply pick out more severe depression, and that a poor response to one drug “doesn’t mean they’ll respond better to a different treatment at all”¹. Whether the clock drives the low mood, or the low mood scrambles the clock, is still open¹.

What is already known. A 2025 review cited in the report found that among more than 800 people with depression that was not seasonal, more than 40% reached remission with bright light therapy, against 25% in the control group; the evidence for melatonin is weaker¹. The Sydney team is now running a melatonin trial in young adults who fit the profile¹.

For you. You don’t need a new diagnosis to use an old remedy: morning daylight, a steady bedtime and a weekend that does not run three hours late are cheap and safe. If low mood has lasted weeks, the right first step is still a GP, not a checklist.