Advances in the genetics of schizophrenia: will high-risk copy number variants be useful in clinical genetics or diagnostics?

Clinical applications of schizophrenia genetics: genetic diagnosis, risk, and counseling in the molecular era

Schizophrenia is a complex neuropsychiatric disease with documented clinical and genetic heterogeneity, and evidence for neurodevelopmental origins. Driven by new genetic technologies and advances in molecular medicine, there has recently been concrete progress in understanding some of the specific genetic causes of this serious psychiatric illness. In particular, several large rare structural variants have been convincingly associated with schizophrenia, in targeted studies over two decades with respect to 22q11.2 microdeletions, and more recently in large-scale, genome-wide case-control studies. These advances promise to help many families afflicted with this disease. In this review, we critically appraise recent developments in the field of schizophrenia genetics through the lens of immediate clinical applicability. Much work remains in translating the recent surge of genetic research discoveries into the clinic. The epidemiology and basic genetic parameters (such as penetrance and expression) of most genomic disorders associated with schizophrenia are not yet well characterized. To date, 22q11.2 deletion syndrome is the only established genetic subtype of schizophrenia of proven clinical relevance. We use this well-established association as a model to chart the pathway for translating emerging genetic discoveries into clinical practice. We also propose new directions for research involving general genetic risk prediction and counseling in schizophrenia.

Predictive and diagnostic genetic testing in psychiatry

The recent advent of commercially available genetic tests for the diagnosis of several mental illnesses has led to intense controversy amongst the psychiatric research community. In this article the authors review these developments, and contrast these with the growing evidence from genomewide association studies that highly heritable psychiatric conditions such as schizophrenia are due to the contributions and interaction of multiple allelic variants, each of small effect size. There is also evidence for the contribution of some highly penetrant rare de novo copy number variants, though the lack of disease specificity for these is of concern. This article outlines the prerequisites for predictive and diagnostic genetic tests, such as clinical validity and utility, and reviews the opportunity that genetic tests for mental illnesses present. As the scientific discourse on genetic tests for complex disorders is not limited to psychiatry, the authors outline current thoughts on the significance of genome-wide association studies across health, and the phenomenon of direct-to-consumer tests in medicine. The attitudes and understanding of patients, families, and clinicians about the future (currently hypothetical) scenario of psychiatric genetic tests are discussed, as is the potential for such testing to increase, rather than diminish stigma. Finally, recommendations on the future development and availability of genetic tests in psychiatry are provided.

Predictive and diagnostic genetic testing in psychiatry

The recent advent of commercially available genetic tests for the diagnosis of several mental illnesses has led to intense controversy amongst the psychiatric research community. In this article the authors review these developments, and contrast these with the growing evidence from genome-wide association studies that highly heritable psychiatric conditions such as schizophrenia are due to the contributions and interaction of multiple allelic variants, each of small effect size. There is also evidence for the contribution of some highly penetrant rare de novo copy number variants, though the lack of disease specificity for these is of concern. This article outlines the prerequisites for predictive and diagnostic genetic tests, such as clinical validity and utility, and reviews the opportunity that genetic tests for mental illnesses present. As the scientific discourse on genetic tests for complex disorders is not limited to psychiatry, the authors outline current thoughts on the significance of genome-wide association studies across health, and the phenomenon of direct-to-consumer tests in medicine. The attitudes and understanding of patients, families, and clinicians about the future (currently hypothetical) scenario of psychiatric genetic tests are discussed, as is the potential for such testing to increase, rather than diminish stigma. Finally, recommendations on the future development and availability of genetic tests in psychiatry are provided.