The Sleep-Depression Connection
"People were used to thinking about psychological states as something really different from our body," says Huda Akil, co-director of the U-M's Molecular & Behavioral Neuroscience Institute and Pritzker Neuropsychiatric Disorders Research Consortium. "The more we study the biology of depression, the more we see they're really closely intertwined."
Akil and other U-M researchers are uncovering the links between depression and circadian rhythms, the biological clocks that make most people energetic in mid-morning, hungry in the afternoon, and tired at night. It turns out that the rhythms of depressed individuals--nearly one in ten Americans--are skewed. That explains their troubled sleep and eating habits, diminished sexual needs, and poor ability to concentrate--and opens a new path to treating mood disorders by resetting sufferers' internal clocks.
U-M genetics prof Jun Li was lead author on a paper reporting the results of a study of fifty brains. The researchers noted the levels of certain hormones present in the brain at the time of death and matched them to those that are active in the brain at a given time of day. Typically, the brain secretes a stress hormone called cortisol in the morning to get ready for the day's activities; at night, melatonin prepares the body for sleep.
For healthy individuals, Li's team was able to develop a formula that correlated hormone levels with the person's time of death. But the formula didn't work for people who had suffered from mood disorders--their hormonal cycles were out of whack.