Variations of a particular gene linked to anxiety and depression could help researchers understand the underlying mechanisms that cause the disorders. Though the research was conducted on marmoset monkeys, researchers say their findings could pave the way for more personalized treatment.
Variations of the serotonin transporter gene (SLC6A4) have been associated with anxiety, depression, and certain mood disorders as well as have been known to impact the efficacy of pharmaceutical drugs aiming to counter such effects. Writing in the Proceedings of the National Academy of Sciences, researchers tested monkeys that exhibited "trait anxiety", a personality characteristic that is linked to such genetic variations in the SLC6A4 and that will influence whether they perceive something as a threat. In humans, trait anxiety has been linked with a higher risk of developing anxiety and mood disorders.
They found that those variations in SLC6A4 impacted the number of specific serotonin receptors in the brain responsible for the uptake of the neurotransmitter in the brain. Particularly, monkeys carrying the variant gene had lower numbers of these receptors, which may play a role in how they perceive threats and how serotonin-based drugs affect them. When given selective serotonin reuptake inhibitor (SSRI) medication, a common antidepressant used for treatment in humans, monkeys carrying the variant gene had an uptick in anxiety in what is known as an “anxiogenic” effect. Human patients often have this in the early stages of their treatment, suggesting that variations in SLC6A4 could be the reason some people do not respond well to SSRIs.
"As many as one in three people affected by anxiety and depression does not respond to anti-depressants, so we need to find better treatments to help improve their quality of life," said study author Andrea Santangelo, from the University of Cambridge, in a statement. "Our research suggests that differences in our DNA may help predict which of us will respond well to these medicines and which of us require a different approach. This could be assessed using genetic testing.”
SLC6A4 is located in a part of the brain called the insula cortex. Here, information about sensations coming from the body is integrated with cognitive information to process feelings, self-awareness, and to help guide a person towards making decisions. The findings suggest not only an underlying mechanism for why some people experience anxiety and mood disorders but also present further evidence suggesting cognitive behavioral therapies (CBT), those directed at retraining thought patterns and responses, may be effective in treating those who don’t respond to SSRIs.