The boundary between mental illnesses may be far more artificial than previously thought. A groundbreaking genomic study, published in late 2025, suggests that many psychiatric disorders classified separately actually share a common biological architecture. Behind the distinct diagnoses, genetics paints a very different picture, where mental vulnerabilities are organized into broad categories rather than isolated pathologies. For decades, psychiatry has been structured around symptom-based classifications. Schizophrenia, anxiety disorders, depression, bipolar disorder, and addictions have been defined as autonomous entities, each with its own criteria and treatments. Yet, clinical practice has consistently revealed significant areas of overlap. A majority of patients diagnosed with one mental disorder develop another during their lifetime, without it being clear whether these disorders coexist or stem from a common underlying condition. This is precisely what genetics is now investigating. By analyzing data from over a million people, researchers have identified deep genetic links between fourteen major psychiatric disorders. Published in the scientific journal Nature, the study shows that these pathologies are not randomly distributed, but are organized around five major genetically coherent groups.
Biological groups rather than compartmentalized diagnoses
The results indicate that certain diseases long considered distinct share numerous genetic variants. Schizophrenia and bipolar disorder thus form a closely related group, while depression, anxiety, and post-traumatic stress disorder cluster around another common core. These groupings are not based on the simple coexistence of symptoms, but on shared biological mechanisms identified at the genome level. The majority of the genetic variants analyzed are not specific to a single disorder. They influence several pathologies simultaneously, challenging the idea of a single cause for each disease. This suggests that the same biological predisposition can manifest in different clinical forms depending on the individual, their history, and their environment. The study also highlights the differentiated role of certain brain cells depending on the group of disorders. Pathologies related to schizophrenia and bipolar disorder are associated with abnormalities primarily affecting excitatory neurons, which are essential for the transmission of nerve signals. Conversely, depressive and anxiety disorders appear to be more closely linked to dysfunctions of glial cells, particularly those that insulate nerve fibers. This cellular distinction reinforces the idea of a deep biological organization, far more structured than current classifications suggest. Researchers working within the Psychiatric Genomics Consortium have also identified particularly active genetic regions, some of which concentrate signals common to several disorders. Chromosome 11 emerges as a key location, notably housing genes involved in dopamine regulation, already known for their role in addictions and certain psychotic disorders.
Towards a redesign of psychiatric thinking
These findings fuel a long-standing debate about the relevance of current psychiatric classifications. While several disorders share a common genetic basis, the proliferation of diagnoses could sometimes mask a single vulnerability expressed in different ways. From this perspective, a patient suffering from anxiety, mood disorders, and obsessive behaviors would not necessarily have multiple illnesses, but rather present a single underlying biological profile. However, the study's authors remain cautious. A common genetic origin does not imply an identical therapeutic response. Effective treatments today often target specific mechanisms and remain essential for individualized care. Genetics, therefore, does not eliminate clinical complexity, but it offers a new framework for understanding it. Ultimately, this genetic mapping could transform prevention and care. Early identification of at-risk profiles would allow for anticipating the onset of comorbidities and developing treatments that address multiple disorders simultaneously. The researchers nevertheless emphasize current limitations, particularly the bias of data primarily derived from European populations, which hinders the universal application of these results. Psychiatry is thus at a pivotal moment. Genetics does not deny the existence of mental disorders, but it redefines their contours. By revealing common roots where we previously saw distinct illnesses, it invites us to fundamentally rethink how we classify, understand, and treat psychological suffering.
