How Can Genetic Research Inform Current Psychiatric Diagnostic Practice?
In February 2013, the cross-disorder group (CDG) of the Psychiatric Genomics Consortium (PGC), published the largest genetic study of mental illness ever done. Scanning the genomes of over 33,000 patients and nearly 28,000 controls, we investigated the possibility that common genetic variants might affect susceptibility to five psychiatric disorders, including autism, ADHD, major depressive disorder, bipolar disorder and schizophrenia. We identified four common genetic risk loci with significant association to all five diseases, including SNPs in two calcium channel genes that regulate the flow of calcium in brain cells. We also found that there were some variants shared by some but not all of the disorders. In August 2013, the CDG/PGC published a second paper that applied quantitative genetic methods to examine the relationships between the five disorders and found substantial evidence for shared genetic etiology among them. These findings raise the questions of how unique and separable these five disorders are and what the relative strengths of unique and shared pathophysiologies might be across the disorders.
This talk will describe how the results of large-scale genomic studies can be used to inform psychiatric nosology, with particular attention to the diagnosis of DSM-V autism/autism spectrum disorder.
Evidence will be reviewed from genome-wide association studies of psychiatric diagnostic categories, such as the ones cited above, as well as studies of quantitative phenotypes, using various molecular and statistical methods.
The genetic studies reviewed provide empirical evidence that genetics/genomics can help us move beyond the design of psychiatric nosological systems based on purely descriptive clinical categories to those informed by biological factors in disease causation. Further, genetic and genomic studies can contribute to the prediction, prevention and treatment of psychiatric diseases such as autism and to the identification of molecular targets for new generations of psychotropic drugs, some of which are likely to cross arbitrarily assigned disease classification boundaries.