Swedish population study reveals that genetic risk for mental illness is significantly less disorder specific than previously assumed

A study of 2 million people reveals schizophrenia is 73% genetically specific, while drug use disorder risk is mostly shared with other psychiatric conditions.

By: AXL Media

Published: Mar 3, 2026, 4:46 AM EST

Source: The information in this article was sourced from Genomic Press

Quantifying genetic overlap in psychiatry

A peer-reviewed study published in Genomic Psychiatry has introduced the metric of "genetic specificity" to determine how much an individual’s inherited risk points toward a specific diagnosis versus a general predisposition to mental illness. Led by Dr. Kenneth S. Kendler of Virginia Commonwealth University, the research team analyzed Swedish national registry data for over two million people born between 1950 and 1995. The study sought to resolve a centuries-old psychiatric debate regarding whether hereditary transmission is tied to individual disorders or represents a diffuse vulnerability to psychopathology.

The hierarchy of genetic specificity

The researchers discovered a wide range of specificity across nine major disorders. Schizophrenia emerged with the highest genetic specificity at 73.1 percent, indicating that nearly three-quarters of the genetic risk carried by affected individuals is unique to that disorder. Bipolar disorder and alcohol use disorder followed in a second tier with specificities of 54.8 percent and 54.1 percent, respectively. In contrast, drug use disorder showed the lowest specificity at just 29.5 percent, suggesting that the majority of genetic risk for addiction actually spills over into other conditions like depression, ADHD, and schizophrenia.

Clinical features that shift genetic profiles

One of the study’s most significant findings is that genetic specificity is not a fixed trait but fluctuates based on clinical characteristics. Across all nine examined disorders, a higher number of recurrences was consistently associated with increased genetic specificity. Furthermore, age at onset played a critical role; for example, early-onset bipolar disorder cases demonstrated much higher specificity than those diagnosed later in life. These findings suggest that the genetic architecture of a mental illness can change depending on the severity and timing of the presentation.