Many psychiatric disorders share symptoms, and most people with a psychiatric diagnosis will be diagnosed with more than one disorder. Due to their frequent co-occurrence, previous studies have suggested that many genetic risk factors are shared between different psychiatric disorders. A new study by the international Cross-Disorder Working Group of the Psychiatric Genomics Consortium was published in Nature on Wednesday.
This study, co-led by dr. Wouter Peyrot (assistant professor, dept. of Psychiatry, Amsterdam UMC), offers the largest and most detailed study to date on the effect of genes on mental disorders (broadly defined). The study examined the genetic effects on fourteen psychiatric disorders from childhood to adulthood. In more than one million individuals with a psychiatric disorder and five million individuals without any of the diagnoses.
“This study brings us closer to a biologically informed map of mental illness, and highlights pathways that could guide future research, prevention, and therapeutics.”
The authors identified five underlying factors that explained most of the genetic signal in the disorders and linked several disorders to each other. These five factors reflected: (i) disorders with compulsive characteristics such as anorexia nervosa, Tourette syndrome and OCD, (ii) schizophrenia and bipolar disorder, (iii) neurodevelopmental disorders, including autism and ADHD, (iv) internalising disorders including depression, anxiety and PTSD, and (v) substance use disorders. Various clinically relevant characteristics, such as suicidality and loneliness, were genetically linked to the five factors. The factors were associated with 238 genetic variants, and these variants pointed to mechanisms in the brain.
These findings represent the most comprehensive analysis to date of the genetic relationships among psychiatric disorders. Demonstrating overlapping genetic foundations that cut across current diagnostic boundaries. The results may inform efforts to align the classification of mental illness with biology. They also suggest potential new targets that could be pursued to develop treatments for commonly co-occurring psychiatric conditions.
“This study brings us closer to a biologically informed map of mental illness,” dr. Peyrot notes. “And highlights pathways that could guide future research, prevention, and therapeutics.”
The article in Nature is published with additional News & Views written by dr. Abdel Abdellaoui (associate professor, dept. of Psychiatry, Amsterdam UMC). Here, dr. Abdellaoui highlights that a substantial amount of the genetic risk for psychiatric disorders reflects normal variation in traits such as cognition, personality and social behaviour. Helping to explain why some genetic factors can relate both to vulnerabilities and to strengths.