Variations in the serotonin transporter gene SLC6A4 directly affect how patients respond to citalopram according to a Mayo Clinic Study just released in the current issue of the American Journal of Medical Genetics Part B: Neuropsychiatric Genetics.

Researchers examined the serotonin transporter gene, or SLC6A4, in 1,914 study participants. The study showed that two variations in this gene have a direct bearing on how individuals might respond to citalopram. SLC6A4 produces a protein that plays an important role in achieving an antidepressant response.

In this study, researchers evaluated the influence of variations in SLC6A4 in response to citalopram treatment in white, black and Hispanic patients. Researchers found that white patients with two distinct gene variations were more likely to experience remission of symptoms associated with major depression. No associations between the two variations and remission were found in black or Hispanic patients.

According to the Centers for Disease Control and Prevention, antidepressants are the most prescribed medication in the country, but many stop taking their medication early because of negative side effects or lack of response. Pharamcogenetic testing looks at genetic variations like SLC6A4 that affect response so medications can be personalized for the patients to help avoid these treatment failures and side effects.

Dr. Mrazek, director of the Genomic Expression and Neuropsychiatric Evaluation (GENE) Unit at Mayo Clinic, stated “first, we started with trial and error - which feels like flipping a coin to select a medication. The Holy Grail would be to be able to consider the implications of variations in many genes. Ultimately, we hope to be able to determine with great accuracy which patients will respond to specific antidepressants and which patients will almost certainly not respond.”