A new large-scale study published in Nature is reshaping how researchers think about psychiatric diagnoses—and it confirms what many clinicians already see in practice.
Rather than existing as entirely separate conditions, mental health disorders may share underlying genetic roots. Researchers analyzed DNA data from more than 1 million people with diagnosed mental illnesses and compared it to data from 5 million individuals without mental health diagnoses. Their findings suggest that many psychiatric conditions fall into five broad genetic categories, each shaped by shared biological pathways.
In other words, different diagnoses may sometimes reflect different expressions of similar underlying processes.
Researchers found that most genetic differences clustered into these groups:
- Compulsive disorders, including anorexia, Tourette disorder, and OCD
- Internalizing disorders, such as depression, anxiety, and PTSD
- Substance use disorders
- Neurodevelopmental conditions, including autism and ADHD
- Bipolar disorder and schizophrenia, which showed significant genetic overlap
These findings help explain why this research matters: more than half of people diagnosed with one psychiatric condition are later diagnosed with another. Often, symptoms overlap across diagnoses. And finally, treatment planning can feel complex and nonlinear for both clinicians and clients
Rather than signaling diagnostic failure, comorbidity may reflect shared biology.
For clinicians, this research reinforces several important realities:
- Clients don’t experience symptoms in neat diagnostic categories
- Flexible, integrative treatment approaches are often necessary
- Focusing on core mechanisms—such as emotional regulation, cognition, or neurodevelopment—may be as important as the diagnosis itself
- Person-centered care remains essential as science evolves
As research continues to evolve, one thing remains clear: understanding what conditions share may be just as important as understanding what sets them apart.