Scientists uncover key reason behind frequent overlap of mental disorders

For decades, diagnosing a mental illness has depended largely on symptoms and clinical observation rather than lab tests. Yet many patients diagnosed with one disorder—such as depression-often develop others like anxiety or substance dependence later in life. The new findings help explain why.

The team analyzed nearly one million individuals with psychiatric diagnoses and compared them to five million without. Using advanced genomic mapping, they identified 428 genetic variants linked to more than one disorder and pinpointed 101 “hot spots” on chromosomes where these shared variants clustered. Statistical models grouped the 14 disorders into five broad clusters-compulsive disorders, internalizing disorders, neurodevelopmental disorders, psychotic disorders, and substance-use disorders.

The results showed especially strong genetic ties between major depression, anxiety, and post-traumatic stress disorder, which shared roughly 90% of their genetic risk. Schizophrenia and bipolar disorder were also closely related, overlapping by about 66%. Further analysis revealed that the same genes often act in similar biological contexts—for example, genes active in oligodendrocytes (cells that insulate nerve fibers) were linked to mood disorders, while those in excitatory neurons were tied to schizophrenia and bipolar disorder.

Experts say these findings mark a turning point for psychiatry. Instead of viewing mental illnesses as distinct categories, this research highlights them as interconnected conditions with shared roots in our DNA. Future treatments, guided by genetic insights, could one day target these overlapping networks to better treat—and even prevent—multiple disorders at once.

REFERENCE: Andrew D. Grotzinger, Josefin Werme, et al.; Mapping the genetic landscape across 14 psychiatric disorders. Nature, 2025; DOI: 10.1038/s41586-025-09820-3