For a long time, doctors and patients were taught to put depression, anxiety or schizophrenia on one side, and diabetes, asthma or heart disease on the other. Two separate worlds, with their specialists, their examinations and their treatments. However, in real life, medical records tell something else, made up of accumulating diagnoses.
The numbers speak for themselves: 41% of people with a psychiatric disorder meet the criteria for at least four disorders, and 38% of the world’s population lives with two or more chronic physical illnesses. A team from the University of Colorado at Boulder has just shown that the same DNA strongly links these pathologies, and the result challenges many preconceived ideas.
A vast common DNA between mental and physical illnesses
Published in February 2026 in the journal Nature Communicationsthe study crossed the genetic material and health data of 1.9 million people. Researchers tracked 73 physical diseases from eight body systems (neurological, respiratory, circulatory, digestive, endocrine/metabolic, genitourinary, musculoskeletal and oncology) and 13 psychiatric disorders grouped into five families (obsessive-compulsive disorders, psychotic/thought disorders, neurodevelopmental disorders, internalizing disorders and substance abuse). Result: genetic risk factors overlap in 42% of cases, one genetic link between mental illnesses and physical illnesses
much stronger than expected.
“What is surprising is not so much the link between psychiatric disorders and medical disorders, but rather the magnitude of this link. At the genetic level, we have seen so much overlap that these are not really two distinct disease categories” says Andrew Grotzinger, assistant professor of psychology and neuroscience and lead author of the study.
Neurodevelopmental disorders such as attention deficit hyperactivity disorder, but also major depression, post-traumatic stress disorder and substance use disorders, are those which most strongly share this genetic terrain with diseases of the body.
Duos of diseases that often go together
In Danish medical records, having a mental health disorder increases the risk of subsequently developing a physical illness by 37% on average, with some combinations rising to almost 400%. People suffering from depression, for example, are 1.5 times more likely to develop heart disease, and the study confirms that depression and anxiety frequently go hand in hand with cardiovascular pathologies.
Other couples highlighted: schizophrenia often appears alongside gastrointestinal problems, while bipolar disorder is commonly associated with genitourinary disorders and insomnia. Conversely, compulsive disorders such as obsessive-compulsive disorder and Tourette’s syndrome are rarely linked to physical illnesses and even seem to protect against digestive disorders.
Shared genes, lifestyles and new treatment options
To explain these links, the authors describe several scenarios. A disorder like depression can promote an unbalanced diet or a sedentary lifestyle, which damage the heart and blood vessels; Conversely, cancer or a serious chronic illness can trigger anxiety and dark thoughts. Sometimes the same DNA fragment simultaneously increases mental and physical vulnerability.
Jeremy Lawrence, a doctoral student in clinical psychology and first author of the study, envisions a future where treatments could simultaneously target physical and mental health. He points to GLP-1 agonists, first created to treat diabetes, then used for weight management, and now showing potential in treating addiction-related disorders, as an example of drugs originally intended for physical illnesses finding their way into the mental health field.
According to Andrew Grotzinger, treating mental disorders can go a long way to improving overall health. “We can ask someone to spit into a tube or take their blood pressure to diagnose a physical illness, but in many ways we have no equivalent for psychiatric disorders. As a result, some consider them more esoteric and less tangible. Psychiatric disorders are just as real as any physical illness. Our results help support this argument.”
explains Andrew Grotzinger.