An international consortium of researchers has classified 14 psychiatric conditions into five major genetic groups, according to a study published in the journal Nature on Mar. 9. The research, which compared common genetic variants across these disorders, is described as the largest of its kind and involved over one million diagnosed cases.
The findings are significant because they offer new insights into how genetics contribute to mental health conditions and may guide future diagnoses and treatments. The classification could also help identify new therapeutic targets and support drug repurposing efforts for psychiatric diseases.
The study identified five main factors based on shared genetic variants. Factor 1 includes compulsive disorders such as anorexia nervosa, obsessive-compulsive disorder (OCD), Tourette syndrome, and anxiety disorders. Factor 2 comprises schizophrenia and bipolar disorder, which share gene expression patterns in brain regions involved in processing reality. Factor 3 relates to neurodevelopmental conditions like autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD), with genes expressed early in brain development. Factor 4 covers internalizing conditions such as depression, anxiety disorders, and post-traumatic stress disorder (PTSD), with genes linked to glial cells rather than neurons. Factor 5 involves substance abuse disorders including alcohol use disorder, nicotine dependence, cannabis use disorder, and opioid use disorder; this group showed stronger associations with socioeconomic indicators such as income and cognitive ability.
Sintia Belangero, a professor at the São Paulo School of Medicine at the Federal University of São Paulo (EPM-UNIFESP) who participated in the study, said: "Our genome has rare and common genetic variants. This study looked only at the common ones, more specifically single nucleotide polymorphisms [SNPs]. This is a category of variants with a major impact on multifactorial diseases, such as psychiatric conditions." She noted that previous work had identified over 100 genes related to schizophrenia.
The research found that Tourette syndrome shares few genetic characteristics with other disorders—87 percent are unique to it—and identified a set of genetic variants present across all analyzed conditions. The analyses were limited to populations of European origin due to data availability but efforts are underway through initiatives like the Latin American Genomics Consortium (LAGC) to increase representation from other populations.
A commentary by Abdel Abdellaoui from the University of Amsterdam stated: "Psychiatric disorders seem to arise more frequently at the extremes of this genetic variation continuum, when certain gene and life experience combinations overlap unfavorably. This should reposition mental illness not as part of defective biology but as the intersection of natural variation and environmental stress." The results reinforce previous evidence about shared genetics among psychiatric conditions using genome-wide association studies.
