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Psychiatric disorders share common genetic risk

Pat Levitt

Study findings published in Science indicate many common psychiatric disorders are connected on a genetic level.

Common genetic risk for psychiatric disorders correlated significantly, especially among ADHD, bipolar disorder, major depressive disorder and schizophrenia; however, most neurological disorders appeared more distinct from each other, according to the results.

“Psychiatric and neurological disorders are given separate names and placed in separate categories, which tends to make one think that each is completely distinct from all others. We know that a specific disorder is recognized because of a cluster of symptoms, there can be overlap between disorders. So, they are not different, but with shared characteristics,” Pat Levitt, PhD, from the Children’s Hospital Los Angeles and Keck School of Medicine of the University of Southern California, told Healio Psychiatry. “Because all psychiatric and neurological disorders are based in part on genetic risk, the study was important to produce scientific evidence that there is overlap of the genetic risk factors for many of these disorders.”

According to authors, directly observable phenomena often distinguish neurological disorders from psychiatric disorders, therefore understanding the genetic foundations and differences for brain disorders and related phenotypes may help determine their biological mechanisms. In this global study, researchers from the Brainstorm Consortium used genome-wide association data from 265,218 patients and 784,643 control participants, as well as 17 phenotypes from almost 1.2 million people, to measure the degree of overlap for genetic risk factors of 25 common brain disorders.

The results showed that certain psychiatric disorders shared a similar genetic foundation, with the strongest connections between ADHD, bipolar disorder, MDD and schizophrenia. Some psychiatric disorders, like major depression and anxiety disorders, also had significant correlations, which may suggest related genetic risk, according to the press release.

In contrast, neurological disorders appeared more distinct from one another compared with psychiatric disorders, which suggested greater diagnostic specificity and dissimilar origins. This excluded migraine, which significantly correlated to ADHD, MDD and Tourette syndrome, the results showed. The neurological disorders that showed particularly little or no correlation with each other and other brain disorders included Parkinson's disease, Alzheimer's disease, epilepsy and multiple sclerosis.

“Clinicians treat symptoms of psychiatric and neurological disorders. The overlap in symptoms is not due to errors in diagnosis. The genetic studies demonstrate a biological basis for the overlap,” Levitt told Healio Psychiatry. “Furthermore, the findings show that the genetic risk correlates with early life measures of cognition, such as educational attainment.”

The study findings also showed that neuroticism was significantly linked to almost every psychiatric disorder and migraine in the general population. In addition, researchers found significant genetic sharing between disorders and early life cognitive measures like years of education and college attainment in the general population, according to the full study. Early life cognitive factors demonstrated a positive correlation with several psychiatric disorders, including anorexia nervosa and bipolar disorder.

“To bring more precision to personalizing treatments, [the physician should recognize] that different individuals with different category of diagnosis may still have some common symptoms,” Levitt said. “This means that certain approaches to treat symptoms in one disorder may be tried for another disorder in a person who may have a shared symptom.” – by Savannah Demko

Disclosure: The authors report no relevant financial disclosures.