In the United States, a study has established a link between five genetic factors and the core of mental disorders (and addictions), including autism, depression, bipolar disorder, and schizophrenia. This represents a major scientific breakthrough that could truly revolutionize psychiatry. Why?
Distinct biological signatures
The Department of Psychiatry at Harvard Medical School (United States) led a vast study published in Nature in December 2025. As part of these monumental efforts, the researchers analyzed the DNA of more than six million people worldwide. Their conclusion: the heritable vulnerability of 14 major psychiatric disorders does not arise from thousands of isolated causes. This vulnerability clusters around five major common genomic factors. It concerns distinct biological signatures affecting different brain functions, capable of explaining on average 66% of the genetic variance of the diseases studied.
“Psychiatric disorders display high rates of comorbidity and genetic overlap, calling into question the current diagnostic boundaries. For disorders whose diagnostic distinction has been the subject of heated debates, such as schizophrenia and bipolar disorder, genomic methods have revealed that the majority of the genetic signal is shared.”, the study notes.
What are these five factors?
First, consider the compulsive disorders factor, a genetic profile altering brain circuits related to impulse control and behavioral rituals. This includes obsessive-compulsive disorder (OCD), Tourette’s syndrome, and anorexia nervosa. Next comes the internalizing disorders factor, influencing the regulation of negative emotions, sadness, and the management of stress in response to the environment. This category encompasses anxiety disorders, major depressive disorder, and post-traumatic stress disorder (PTSD).
The researchers then described the neurodevelopmental factor, involving genes that activate very early (in the womb), disrupting the initial establishment of synaptic connections. This concerns autism spectrum disorders (ASD) and attention-deficit/hyperactivity disorder (ADHD). Then comes the category “Schizophrenia and Bipolar Disorder,” two diagnoses long treated as separate by psychiatry. Yet the study found that these conditions shared 70% of their genetic signal, largely affecting the brain’s excitatory neurons.
Finally, the authors identified a last factor, namely those disorders linked to substance use. This genetic group regulates the brain’s reward system and the mechanisms of neural habituation, increasing the risk of addiction to alcohol, nicotine, cannabis, and other opioids.
In what way is this study revolutionary?
For the American researchers, their discovery truly marks a revolution in psychiatry. This concerns particularly the explanation of comorbidities. From now on, science finally understands why a patient often suffers from several disorders at once—for instance, OCD and anorexia simultaneously: they share the same genetic root. The advancement also lies in cross-cutting treatments. Indeed, instead of developing a drug for a single disease, it will be possible to develop therapies targeting the genetic factor common to several disorders. In the case of OCD and anorexia together, an effective treatment for one should help in treating the other.
Finally, the study’s conclusions should enable redefining the diagnostics of the various disorders. Indeed, the strict boundaries of the latest version of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) dating from 2013—the psychiatric reference manual—could give way to a new classification based on the brain’s real biology.
