Researchers collected blood samples from 30 people with a history of depression and 30 people who had never been diagnosed with the disorder. The blood samples were analyzed to assess messenger RNA levels related to four circadian genes. Messenger RNA levels indicate gene activity.
Participants with a history of depression had a higher level of activity of the gene known as the Clock gene than those who had never had depression. Increased activity of the Clock gene suggests a problem with the 24-hour biological and behavioral cycle, which could affect sleep patterns and other physical functions governed by circadian rhythm, the researchers said.
“We know that there are a lot of insomnia symptoms in depression, especially early morning awakening,” lead author Jean-Philippe Gouin, a graduate student in psychology at Ohio State University, said in a university news release.
“We can’t say with this study that there is a direct relationship between this altered gene function and behavior, but the research suggests that over-expression of circadian genes might serve as a biomarker of vulnerability to depression,” Gouin added.
The study was published in a recent issue of the Journal of Affective Disorders.
The findings suggest that people with depression who have increased Clock gene activity might get the most benefit from sleep-related treatments, such as light therapy or antidepressants that affect the hormone melatonin, which regulates sleep.