Scientists have found a link between depression and an alteration in the body’s so-called Clock gene, which plays a role in regulating circadian rhythm.
The Ohio State University research found more activity in the Clock gene in individuals who had experienced depression than in participants with no history of mood disorders.
“We know that there are a lot of insomnia symptoms in depression, especially early morning awakening,” said Jean-Philippe Gouin, lead author of the study and a graduate student in psychology at Ohio State University.
Higher activity levels of this gene suggest something is wrong with the body’s 24-hour biological and behavioral cycle, and in turn could create sleep disturbances — a common symptom of depression — and affect other physiological functions regulated by circadian rhythm.
However, the researchers emphasize that even though there is an association between the gene’s activity and depression, there is no proven cause and effect in either direction. The gene activity could trigger depression or depression could affect the gene expression, or some completely separate environmental or biological factors could combine to alter the circadian rhythm.
If additional research takes place to support these findings, sufferers of depression might be offered new types of therapies. For example, those with depression who have this gene difference might find relief from sleep-related treatments, including light therapy or an antidepressant that affects melatonin, a hormone that regulates sleep.
“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,” said Gouin.
“There was some evidence that chronic stress led to changes in circadian gene expression in animals,” he said. For humans, the researchers decided to look at the chronic stress experienced by those caring for someone with dementia.
“We found that care-giving was not related to circadian genes, but instead it was really the history of depression that distinguishes between regulation of these genes,” Gouin said.
For the study, blood samples were all taken at the same time in the day to control for circadian variations. They were collected from 60 participants, each of whom also participated in an interview.
Thirty of these participants had a lifetime history of depression, while the other half had never been clinically depressed. Twenty-five were taking care of a family member with dementia at least five hours per week and 35 were non-caregiving controls with similar demographic traits.
Their blood was analyzed to determine the messenger RNA levels for four circadian genes, including Clock. The depressed volunteers had a far higher level of Clock mRNA expression than the non-depressed individuals. There were no statistically significant results for the other three genes.
The link between elevated Clock mRNA levels and depression remained when figures were adjusted for differences in age, sex, body mass index, exercise, alcohol and tobacco use, other medical conditions and care-giving status, Gouin added.
Gouin believes that further research needs to be carried out over an extended time period in order to measure the changes in mRNA expression during a 24-hour cycle.
“If we look at people who have depression, they can have very different groups of symptoms. So if some of them have a biological profile that shows circadian dysfunction, there is a chance that a circadian type of treatment might be more helpful for them than for others,” Gouin said.
This study is published in the Journal of Affective Disorders.
Source: Ohio State University