Catherine Griffin

Are you depressed? (Photo : Facebook/Insomnia)

Are you depressed? (Photo : Facebook/Insomnia)

It turns out that subtle changes in a single gene can predict how the brain reacts to stress. The findings could have huge implications for health issues such as depression, post-traumatic stress disorder and obesity.

The researchers focused on two longitudinal studies in particular for this work. In these studies, the scientistsexamined the serotonin transporter, which is a gene that regulates the amount of serotonin signaling that occurs between brain cells and is frequently the target forantidepressant drugs. More specifically, the researchers found that there was a mechanism impacting the brain that may also play a role in an individual’s reaction to stress, which may be a stronger predictor of stress than DNA sequencing.

Attached to the serotonin transporter’s DNA are chemical marks called methyl groups. These help regulate when, where and how much of the gene is expressed. In addition, DNA methylation are one form of gene modification, which scientists are studying to understand how the same genetic code can produce a wide range of cellular responses in the body.

“Varying the DNA sequence in this gene has been shown to predict activation in the amygdala and is linked with depression, so we were interested in determining if DNA methylation may be playing a role in regulating how the brain responds to stress, ultimately making an individual vulnerable to stress-related disorders like depression,” said Douglas Williamson, one of the researchers, in a news release.

The scientists performed imaging on the brains of 80 participants. The volunteers were shown either angry or fearful faces, and then the scientists recorded the responses from the amygdala. The researchers also measured the amount of methylation on serotonin transporter DNA from the participants’ saliva.

So what did they find? Even small changes in methylation corresponded with amygdala activity. This, in turn, appeared to be a better predictor of the risk of depression than DNA sequence variation.

“Our work is helping to identify the specific mechanisms that are involved in the onset of depression, which is involved in 70 percent of people with PTSD,” said Williamson. “Ultimately, we hope that our findings will lower the risk of developing depression and other stress-related disorders in the future.”

The findings are published in the journal Nature.

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