Genetic Relationship between Five Major Psychiatric Disorders
EVE SHARIFI Until recently, the genetic etiology of major psychiatric disorders had largely remained unknown. Even though the major psychiatric disorders, such as schizophrenia and major bipolar disorder,are moderately-to-highly heritable, specific gene abnormalities associated with each disorder could not be found. The current classification of psychiatric disorders in the Diagnostic and Statistical Manual of Mental Disorders (DSM-V) is largely based on clinical symptoms. One of the major issues in the diagnosis of psychiatric disorders is that their symptoms are often shared with other psychiatric disorders. For example, psychosis occurs in both schizophrenia and bipolar disorder. This issue can make diagnoses inaccurate and unreliable. Identifying the genetic architecture of psychiatric disorders can lead to more accurate diagnoses based on underlying genetic aberrations and help in the development of effective gene therapy techniques.
One of the most heritable psychiatric disorders is schizophrenia. This is a severe, chronic psychiatric disorder that affects 1% of the population at some point in their lifetime. Its main symptoms include hallucinations, delusions, disorganized speech, impaired executive functioning, and problems with working memory. Recently, genetic research in schizophrenia has shifted to studying its associated endophenotypes (Turetsky, 2007), or symptoms of an illness that reflect the actions of susceptible genes that may still exist in the absence of a diagnosable pathology.
Studying the genetic variants that influence the various symptoms of schizophrenia has led researchers to interesting findings about the genetics of other major psychiatric disorders. Genetic variation between schizophrenia, major depressive disorder, bipolar disorder, autism spectrum disorders, and attention deficit hyperactivity disorder (ADHD) was explored using the largest genome-wide association study to date (Cross-Disorder Group of the Psychiatric Genomics Consortium, 2013). This project searched for single nucleotide polymorphisms (SNPs), which are variations in a single nucleotide in a given DNA sequence among members of a population. Common SNPs found among these five psychiatric disorders have shed light on the familial heritability of these disorders and why they have overlapping symptoms. These findings will help in the reclassification of these disorders based on firmer empirical footing instead of simply on clinical symptoms. Additionally, this research provides the beginnings for further analysis on the shared pathophysiology of major psychiatric disorders and potential common therapeutic techniques.
References: Cross-Disorder Group of the Psychiatric Genomics Consortium. "Genetic relationship between five psychiatric disorders estimated from genome-wide SNPs." Nature genetics 45.9 (2013): 984-994.
Turetsky, Bruce I., et al. "Neurophysiological endophenotypes of schizophrenia: the viability of selected candidate measures." Schizophrenia bulletin 33.1 (2007): 69-94.