The researchers analyzed the brains of people who died suddenly, due to heart attacks or car accidents, and found that while they were able to estimate the time of death of the individual by studying the genetic state of the brain, they were unable to do so among people who suffered from depression.
The researchers said that the genetic state of the brain bore little resemblance to the hour of their death, indicating the possibility that they suffered from severely disrupted sleeping pattern.
"We think the depressed individuals are more likely to be out-of-sync with the regular wake-sleep timing. Our data also suggests that their daily cycles are not only shifted, but also disrupted. That is, they sleep by the wrong clock, and when they do sleep, the quality [of sleep] could be different from normal sleep", lead researcher Jun Li said.