Pharmacogenetics—A Useful Tool in Antidepressant Pharmacotherapy?

Major Depressive Disorder (MDD) is a highly disabling disease characterized by a lifetime prevalence of 5%–25%, with women being affected approximately twice as often as men. Family and twin studies indicate a strong genetic contribution to the pathogenesis of MDD with an estimated heritability of 40%–50%. Antidepressive pharmacotherapeutic agents such as tricyclic antidepressants (TCA), selective serotonin reuptake inhibitors (SSRI), norepinephrine and serotonin reuptake inhibitors (SNRI) or noradrenergic and specific serotonergic antidepressants (NaSSA) have proven to be highly effective for a large proportion of patients in the treatment of major depression. However, two major issues need to be addressed in the pharmacotherapy of MDD, treatment resistance and treatment intolerance. Treatment Resistance A full 30%–40% of all patients fail to respond sufficiently to initial pharmacotherapy treatment. Since it can take several weeks after treatment initiation for these agents to exert antidepressant effects, patients might have to endure this period of time without symptom relief before the antidepressant is known to be ineffective. Thus, it would be highly beneficial for providers to be able to identify non–responders to a