The University of Colorado Boulder announced on Apr. 8 new research showing that the same genetic factors underlying psychiatric disorders such as depression, post-traumatic stress disorder, and attention deficit hyperactivity disorder are also associated with a range of physical diseases.
This finding challenges the long-standing separation between mental illness and physical disease in medical practice. The study, which analyzed data from nearly two million people and was published in Nature Communications, highlights how often these conditions overlap genetically.
Jeremy Lawrence, a PhD candidate in clinical psychology and first author of the study, said: "In the clinic, you rarely see someone with just one condition walk into a room. If we can better understand the cross-talk between these conditions, we can do a better job helping the whole patient." The researchers examined DNA associated with 73 physical outcomes across eight medical domains as well as 13 psychiatric disorders across five categories. They found that genetic risk factors overlapped between physical and mental disorders 42% of the time.
Lawrence said: "We found that, at the genetic level, the shared risk between psychiatric and non-psychiatric medical disease is pervasive and substantial." The study revealed that neurodevelopmental disorders like ADHD had more genetic overlap with physical diseases than with other psychiatric conditions. Major depression, PTSD, and substance use disorders also showed high levels of shared risk with various physical illnesses. In contrast, compulsive disorders such as obsessive-compulsive disorder appeared to have little association or even a protective effect against some digestive issues.
The research identified specific pairings among diseases: schizophrenia often occurred alongside gastrointestinal problems; bipolar disorder paired with genitourinary issues and sleep problems; while depression and anxiety were linked to cardiovascular disease. Lawrence explained that behaviors related to mental illness could lead to poor physical health or vice versa due to lifestyle changes after diagnoses or direct genetic influence on both types of conditions.
Looking ahead, Lawrence suggested therapies might be developed to target both mental health concerns and related physical ailments simultaneously. He cited GLP-1 agonists—drugs initially created for diabetes but now being considered for weight loss and substance abuse—as an example where treatments cross traditional boundaries between fields.
For now, addressing mental illness remains key to improving overall health outcomes according to Grotzinger. He said: "You can ask someone to spit in a tube or put a blood pressure cuff on to diagnose physical illness, but in many ways we don't have that for psychiatric disorders so some have viewed them as more esoteric and less tangible... Psychiatric disorders are just as real as any medical disease. Our findings help make that argument."
