Shared Genes May Link ADHD, Autism, and Depression
So, looking for these genes in an individual now would not be considered a diagnostic tool. "They are not enough to predict any individual's risk. And you might carry all of these variants and never develop a psychiatric disorder," Smoller said.
However, the new findings add to the understanding of these conditions and may help in developing new treatments, he explained.
"It could also change the way we define and diagnose these disorders, based on the biological causes," Smoller said. "Some of the disorders we think of as clinically distinct actually have more of a relationship than we might have thought."
Two experts not connected to the study agreed.
"This is the first genome-wide evidence showing that neuropsychiatric diseases share genetic risk factors," said Eva Redei, professor of psychiatry at the Feinberg School of Medicine at Northwestern University in Chicago.
She noted that all five of the conditions tackled in the study can share certain clinical features and symptoms, including variation in mood, mental impairments, and even psychosis.
"Therefore, the question is whether the identified shared genetic risk factors are related to the diseases or to the shared clinical symptoms," Redei said. "Shared genetic contribution can identify some key regulators in the brain, and can also help to find new drug targets," she said.
Simon Rego, director of psychology training at Montefiore Medical Center at the Albert Einstein College of Medicine in New York City, agreed that the findings are "an important next step" in understanding mental illness.
As more gene studies are conducted and analyzed, scientists will "be in a better place to identify shared cause of psychiatric disorders at a molecular level," he said. "Ultimately, [this could] generate new models for drug interventions and possibly even prevention."
For more information on mental disorders, visit the U.S. National Institute of Mental Health.