Progressing towards precision psychiatry: current challenges in applying biomarkers in psychiatry

After decades of fundamental research into the neurobiological and genetic origins of psychiatric disorders, the field has progressed into a thrilling new era, being driven by the concept of precision psychiatry (see Figure 8.6.1). Although precision medicine takes interindividual differences in genetic, environmental, and life style factors into account (e.g., in prevention, diagnostics, and treatment: National Research Council, 2011), psychiatry seems not to have harvested the potential of advanced, personalized, diagnostics and therapeutic technologies to the extent other fields of medicine have done (Fernandes et al., 2017). Due to an immense body of scientific findings, the number of potential biomarkers in psychiatry is nevertheless considerable, though diverse, divergent, and unstructured. Ideally, a biomarker should be present before the onset of symptoms; accurately discriminate non-risk individuals from individuals at risk (sensitivity); and should be specific for a well-defined disorder (Yerys & Pennington, 2011). In psychiatry, most candidates unfortunately fail however, generally on the last criterion (disorder specificity). This implies that, notwithstanding considerable efforts, nearly 40 years of Diagnostic and Statistical Manual of Mental Disorders (DSMs) seem to have failed to convincingly connect mental disorders to biology (e.g., Yee et al., 2015). As a result, in the field of psychiatry remarkably few claimed “biomarkers” have matured into more or less standardized methods supporting clinical decision-making, like diagnostics 1 and outcome monitoring. A conclusion that arguably inflates the reach of the biomarker concept, at least in the context of mental health because “biomarker” does not seem to have a consistent meaning beyond “correlate,” although it is often used as if it would carry more significance than that (Miller et al., 2016).