The serotonin (neurochemical) system in the brain has long been a target for interventions aimed at reducing depression and stress. Selective Serotonin Reuptake Inhibitors (SSRIs) are often used to balance mood and counteract high levels of anxiety. It is not surprising then that scientists are now finding that individual differences in the genetic makeup of this serotonin system may have a significant impact on one’s vulnerability to mental illness.

Individual differences in the genetic makeup of the serotonin system have been shown to increase one’s vulnerability to depression, anxiety and other psychiatric conditions, particularly if individuals are exposed to stressful events in their lives. Studies are showing that certain people (those that have the short allele of the serotonin transporter gene) have a greater biological reactivity to stressful events, including a larger hormonal response to stress and a greater brain reactivity to threat. In other words, both the hormonal and brain systems (amygdala) involved in fear and anxiety are more active in response to stress in those individuals who have a certain genetic makeup (short allele). This genetic difference may also account for individual differences in personality; those people who have a short allele for the serotonin transporter have been suggested to exhibit more “anxious” personality traits. This means our differences in gene function may bias our brains and our personalities to create a tendency to be more “negative,” “anxious” or reactive to stress.

This begs the question: should modern medicine and psychotherapeutic approaches be extended to better account for these individual genetic variations in the stress response (and the serotonin system)? The idea that we may be able to refine our approach to medicine to account for these types of individual differences (in genetics, personality, the stress response and beyond) is pertinent to the continuing evolution of medicine and science, and one that is indeed increasingly being adopted by clinicians interested in a “personalized medicine” approach to traditional medical treatment and other forms of therapy. Furthermore, looking at a person’s biological make-up has applications for being able to better predict which individuals may be more at risk for mental health difficulties.

While the idea that our genetics may be used to tailor our individual medical treatments and to screen us for vulnerabilities could appear to some like a vision from the movie Gattaca (1997 science fiction film), such refinement in our medical approach may prove to be a significant step forward.

References

I GOTLIB, J JOORMANN, K MINOR, J HALLMAYER (2008). HPA Axis Reactivity: A Mechanism Underlying the Associations Among 5-HTTLPR, Stress, and Depression Biological Psychiatry, 63 (9), 847-851 DOI: 10.1016/j.biopsych.2007.10.008

M MUNAFO, S BROWN, A HARIRI (2008). Serotonin Transporter (5-HTTLPR) Genotype and Amygdala Activation: A Meta-Analysis Biological Psychiatry, 63 (9), 852-857 DOI: 10.1016/j.biopsych.2007.08.016

B S Shastry (2005). Pharmacogenetics and the concept of individualized medicine The Pharmacogenomics Journal, 6 (1), 16-21 DOI: 10.1038/sj.tpj.6500338