London - People with severe depression have a disrupted “biological clock” that makes it seem as if they are living in a different time zone to the rest of the healthy population living alongside them, a study has found.
It is the first time that depression has been linked unequivocally to the internal circadian clock of the human brain, which regulates the body's day-and-night cycle over a 24-hour period, scientists said.
The researchers found that they could estimate a healthy person's time of death to within a few hours by analysing the activity levels of a set of genes within certain regions of the deceased brain.
However, this correlation broke down when they analysed the autopsied brains of people who had suffered from depression. Their gene activity bore little relationship to the hour of death, which indicated they suffered a severely disrupted sleeping pattern, the scientists found.
The findings suggest that patients with severe depression could be better treated if there was some way of improving the relationship between the daily cycle of brain gene activity with the actual time of day or night, they said.
“We think the depressed individuals are more likely to be out-of-sync with the regular wake-sleep timing,” said Jun Li of the University of Michigan, the lead author of the study published in the journal Proceedings of the National Academy of Sciences.
“Our data also suggests that... they sleep by the wrong clock, and when they do sleep, the quality could be different from normal sleep. If we can understand how depression and poor sleep reinforce each other, we may be able to find better treatment, perhaps by finding better ways to break the cycle.”
Huda Akil, a co-author of the study, said: “In depressed people, [a disrupted biological clock] can become part of a vicious cycle. Therefore, one can speculate that re-setting the clock, for instance with light or physical activity, is a reasonable, concrete target to aim for in the treatment of severe depression.” - The Independent