5 Psych Disorders Have Common Genetics

Autism, attention deficit-hyperactivity disorder (ADHD), bipolar disorder, major depressive disorder, and schizophrenia share common genetic underpinnings -- despite differences in symptoms and course of disease, researchers discovered.

In particular, single nucleotide polymorphisms (SNPs) in two genes involved in calcium-channel activity appear to play a role in all five, Jordan Smoller, MD, ScD, of Massachusetts General Hospital in Boston, and colleagues reported online in The Lancet.

The findings come from a genome-wide analysis of 33,332 cases and 27,888 controls in what the authors described as the largest-ever genetic study of psychiatric illness.

The results are "new evidence that may inform a move beyond descriptive syndromes in psychiatry and towards classification based on underlying causes," Smoller said in a statement.

The findings are especially important because of revisions to the Diagnostic and Statistical Manual of Mental Disorders and the International Classification of Diseases, which have "reinvigorated debate about the validity of diagnostic boundaries," the authors noted.

Indeed, the findings confirm previous evidence of "abundant pleiotropy in human complex disorders" – meaning the same genetic variant plays a role in several diseases, argued Alessandro Serretti, MD, PhD, and Chiara Fabbri of the University of Bologna in Italy.

For instance, they noted in an accompanying commentary, calcium signaling, a key regulator of the growth and development of neurons, was expected to be highly pleiotropic, an expectation that "has now been confirmed."

The findings in this study show that specific single-nucleotide polymorphisms are associated with a range of psychiatric disorders of childhood onset or adult onset. In particular, variation in calcium-channel signalling genes seems to play a role in five psychiatric disorders.

But while some gene variants play a role in many disorders, there are almost certainly others that contribute to the "consistent diversity among disorders," Serretti and Fabbri argued.

"Many genes and polymorphisms are expected to confer a liability to individual psychiatric diseases," they wrote.

Nonetheless, they concluded, one implication of the study is that genetics "can contribute to prediction and prevention of psychiatric diseases, along with the identification of molecular targets for new generations of psychotropic drugs."

But that is not likely to happen soon, according to Randy Ross, MD, of the University of Colorado School of Medicine in Aurora, Colo.

The study is a "beginning step to give us ideas that will eventually lead to new treatments," he told MedPage Today.

In the long run, however, this study and subsequent research will change both diagnosis and treatment, Ross said, as psychiatric diseases are put on a biological footing.