Psychiatric disorders share genetic roots, explains why some have multiple diagnoses: VCU study

RICHMOND, Va. (WRIC) -- A new study from Virginia Commonwealth University (VCU) shows 14 psychiatric disorders share genetic roots, which can explain why some people have multiple diagnoses.

The study, "Mapping the genetic landscape across 14 psychiatric disorders," published on Wednesday, Dec. 10, in the journal Nature and co-chaired by Kenneth Kendler, a professor at VCU, detailed an analysis of genetic roots shared among 14 conditions, with five families of disorders experiencing high levels of overlap.

Most people diagnosed with a psychiatric disorder will be diagnosed with a second or third, leading to significant challenges for treating conditions.

Though experts said a person's environment and experiences influence the possibility of being diagnosed with multiple disorders, experts emphasized that their genetic makeup plays a significant role.

According to a release, after analyzing data from over 6 million people, the working group mapped the genetic landscape of 14 psychiatric conditions and unveiled five families of disorders with high levels of genetic overlap.

The research group analyzed genetic material from more than 1 million people with childhood- or adult-onset psychiatric disorders and 5 million individuals without a disorder diagnosis.

“Psychiatry is the only medical specialty with no definitive laboratory tests. We can’t give a blood test to tell whether someone has depression – we have to rely on symptoms and signs. And that’s true for almost every psychiatric disorder,” Kendler said. “Genetics is a developing tool that allows us to understand the relationships between disorders. The findings from this study reflect the most comprehensive analysis of psychiatric genomic data to date and shed new light on why individuals with one psychiatric disorder often have a second or third.”

The following are the five groups based on genetic similarities:

• Compulsive disorders: obsessive-compulsive disorder, anorexia nervosa, and to a lesser extent, Tourette disorder and anxiety disorders.
• Internalizing disorders: major depression, anxiety disorders and post-traumatic stress disorder.
• Neurodevelopmental disorders: autism spectrum disorder, attention-deficit/hyperactivity disorder and, to a lesser extent, Tourette disorder.
• Schizophrenia and bipolar disorder
• Substance use disorders: opioid use disorder, cannabis use disorder, alcohol use disorder and nicotine dependence.

Major depression, anxiety and post-traumatic stress disorder (PTSD) had particularly high genetic overlap, with about 90% of genetic risk believed to be shared across all three conditions.

VCU data shows that schizophrenia and bipolar disorder share about 66% of their genetic markers.

“I feel very proud to be a part of this effort,” Kendler said. “This work really shows that we gain more for our field and for those suffering from mental illness when we come together to tackle these scientific challenges.”