Psychiatric disorders affect more than 1 billion people globally and are among the leading causes of disability worldwide in all age ranges from 5 to 75 years.1,2 A careful clinical evaluation is the first step in making an accurate diagnosis and treatment decision. However, the complexity of many cases or the effect of unmeasured biological markers (biomarkers) may make this approach difficult. Various psychotropic medications belonging to different classes are available, which contributes to the difficulty in making treatment decisions. Consequently, multiple drug switches or combinations/augmentations are a frequent practice and months may be required before finding an effective and well-tolerated treatment.3 Approximately 50% of patients with depression do not respond to at least one antidepressant.4 Moreover, poor treatment adherence often due to adverse effects is frequent and may be one of the causes of treatment resistance.5
In this scenario, the use of biomarkers, and specifically genetic variants, to tailor treatment to the individual is an option to improve mental health care by increasing remission rates and reducing the incidence of adverse effects. Genetic variants are involved in the inter-individual differences in psychotropic drug pharmacokinetics and pharmacodynamics. Compared with other types of biomarkers such as neuroimaging brain measures or plasma proteins, genotyping has several advantages: it is easy and quick to perform (the patient can collect the sample using a saliva kit at home), it is economically affordable, and the information generated does not change over time and can be used life-long. These facts explain why psychiatric pharmacogenetics has become a central interest for academic and non-academic institutions and of course for patients and caregivers.
The circumstances requiring the prescription and/or interpretation of a pharmacogenetic test are becoming more and more frequent in everyday psychiatric clinical practice. In some cases, a patient may come for the initial visit to a psychiatrist’s office with the results of a pharmacogenetic test. He or she asks for “the right” prescription based on the results. Some key questions arise at this point: is this test the best option to guide treatment choice in this patient? How to translate the information into a prescription?
In other cases, it might be the clinician who wonders if pharmacogenetic testing should be recommended: for example, in a patient with a history of treatment resistance or poor tolerability to several drugs. The answers are not always straightforward.
Dr Fabbri is a Postdoctoral Research Fellow, Social, Genetic, and Developmental Psychiatry Centre, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, UK; Dr Serretti is Professor of Psychiatry, Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy. Dr Fabbri reports no conflicts of interest concerning the subject matter of this article. Dr Serretti reports that he is/has been a consultant/speaker for Abbot, Abbvie, Angelini, Astra Zaneca, Clinical Data, Boheringer, Bristol Myers Squibb, Eli Lilly, GlaxoSmithKline, Innovapharma, Italfarmaco, Janssen, Lundbeck, Naurex, Pfizer, Polifarma, Sanofi, and Servier.
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