Five common psychiatric disorders – bipolar disorder, attention deficit-hyperactivity disorder (ADHD), autism, major depressive disorder, and schizophrenia – have been found to have the same genetic risk factors.

Specifically, two variations in genes play a role in the balance of calcium in brain cells and are a common factor in a few of these disorders, and may be a goal for new treatments.

These new findings, published in The Lancet, are from the biggest genetic study analyzing psychiatric illness, and could aid in eventually identifying these disorders based on what causes them, rather than their symptoms.

Jordan Smoller from Massachusetts General Hospital in Boston, one of the lead researchers explained:

“This analysis provides the first genome-wide evidence that individual and aggregate molecular genetic risk factors are shared between five childhood-onset or adult-onset psychiatric disorders that are treated as distinct categories in clinical practice.”

In an attempt to analyze the potential of common genetic markers – or nucleotide polymorphisms (SNPs) – that could influence susceptibility to the five disorders, the Psychiatric Genomics Consortium (PGC) reviewed the genome of 33,332 patients and 27,888 control subjects of European descent.

They found four risk gene mutation positions that have significant and similar associations with all five diseases or disorders – regions on chromosomes 3p21 and 10q24, and SNPs in two genes that make up parts of channels that control the flow of calcium in the brain cells.

The polygenic risk scores verified cross-disorder outcomes, most notably between adult-onset disorders: schizophrenia, major depressive disorder, and bipolar disorder.

More in depth examination confirmed that calcium channel activity is a significant factor in the development of all five disorders.

Smoller said:

“Significant progress has been made in understanding the genetic risk factors underlying psychiatric disorders. Our results provide new evidence that may inform a move beyond descriptive syndromes in psychiatry and towards classification based on underlying causes. These findings are particularly relevant in view of the imminent revision of classifications in the Diagnostic and Statistical Manual of Mental Disorders (DSM) and the International Classification of Diseases (ICD).”

In a linked editorial comment, Alessandro Serretti and Chiara Fabbri from the University of Bologna in Italy mentioned:

“the present study might contribute to future nosographic [classification] systems, which could be based not only on statistically determined clinical categories, but also on biological pathogenic factors that are pivotal to the identification of suitable treatments.”

The authors conclude that with these new findings, psychiatric diseases or disorders could be predicted and prevented by genetics in the future.

Geneticists are starting to identify gene variants that occur in several psychiatric disorders and/or diseases. Scientists from The Children’s Hospital of Philadelphia said they found 25 extra gene variants occurring in some people with an autism spectrum disorder.

Written by Kelly Fitzgerald