Over the last decade, pharmacogenetics has become increasingly significant to clinical practice. Psychiatric patients, in particular, may benefit from pharmacogenetic testing as many of the psychotropic medications prescribed in practice lead to varied response rates and a wide range of side effects. The use of pharmacogenetic testing can help tailor psychotropic treatment and inform personalized treatment plans with the highest likelihood of success. Recently, many studies have been published demonstrating improved patient outcomes and decreased healthcare costs for psychiatric patients who utilize genetic testing. This review will describe evidence supporting the clinical utility of genetic testing in psychiatry, present several case studies to demonstrate use in everyday practice, and explore current patient and clinician opinions of genetic testing. 1. Introduction Mental illnesses are extremely prevalent and debilitating. Depression alone is the leading cause of disability worldwide, leading to a significant patient/economic burden, affecting at least 350 million people [1]. Approximately 14% of the global disease burden can be attributed to neuropsychiatric disorders [2]. Twenty-five percent of adults in the US currently suffer from a mental illness, and at least half will develop one or more in their lifetime [3]. Moreover, 50% of patients suffering from depression do not respond to first-line therapies or experience severe adverse reactions to medications [4]. There is significant interindividual variation to psychotropic treatment response, leading psychiatrists to adopt a trial and error approach to treatment [5]. Genetic variability can account for much of this inconsistency in medication response [6]. Knowledge of a patient’s genetic background can help clinicians provide a personalized medicine strategy by predicting both drug response and risk for adverse events [7]. Clinicians can utilize this information to compensate for a gene defect (pharmacodynamic genetic variations) or to adjust medication dosage to accommodate the rate at which the patient metabolizes different medications (pharmacokinetic genetic variations). Much of the utility of pharmacogenetic testing has been shown in clinical settings other than psychiatry. Many of these tests identify mutations relating to altered expression and functions of genes associated with drug disposition and response and have been useful in clinical practice [8]. Within psychiatry, several studies have found genetic variations associated with altered treatment response/efficacy [9, 10] and
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