The very Earth we live on has a rhythm all its own. Every morning the sun comes up, the animals start scurrying about, the nocturnal ones hit the hay, flowers bloom and a new day is set into motion. And every night the process reverses itself. Humans are – for the most part – not immune to this natural rhythm. Sure you’ve got some lunatics out there dancing for a month straight or watching four days of 24 straight, but most of his adhere to this phenomenon known as the circadian clock.
As it turns out, this isn’t just a habit we follow because it’s harder to drive at night. This pattern is engrained in our DNA and expressed through multiple genes in our brain, as well as many other organs. And since it’s hardwired, there is always the chance that our circuitry can get messed up, resulting in unpredictable side effects.
Jean-Philippe Gouin of the Ohio State University has a guess as to what one of those side effects may be, however. In a paper recently published in the Journal of Affective Disorders, Gouin explored the possibility that some circadian genetic errors might cause people to be more prone to depression.
To test the hypothesis, Gouin and her team took samples of blood already being provided by 60 elderly patients with an average age of 72 through their daily care activities. Some of these patients had been diagnosed as clinically depressed in their lifetimes and some had not. In order to control for normal daily changes in their blood work, the samples were all taken between the hours of nine and eleven in the morning. She then tested these samples for how active the expression of four circadian genes were during those times: Clock, Period1, Bmal 1 and Period2.
The results showed that three of these genes were over-expressed in the patients who had been depressed. But one gene stood out above them all. The abundance of Clock mRNA levels was a clear independent predictor for which patients had been depressed, even after factors such as health and medications were taken into account.
As of now, this just shows a correlation between depression and an over-activity of this gene. Gouin suggests future studies where participants would be in a controlled environment for 24 hours so that other variables such as exposure to light and social zeitgebers could be regulated. And while it could just be that depression caused the gene to go wild, Gouin suggests that combinations of mutations to circadian clock genes are likely good indicators for risk of future depression.