Scientists have identified the five psychiatric disorders, bipolar disorder, major depressive disorder, schizophrenia, autism and attention deficit-hyperactivity disorder (ADHD), share a common genetic link.

They showed substantial overlap of genetic risk factors shared between bipolar disorder, major depressive disorder and schizophrenia and less overlap between those conditions and autism and attention deficit-hyperactivity disorder ( ADHD).

They are now moving toward understanding the molecular underpinnings of psychiatric illness.

The findings provide insight into the biological pathways that may predispose an individual to disease and could ultimately lead to the development of new therapeutic avenues to treat the five major psychiatric illnesses.

Study co-senior author Kenneth S. Kendler, M.D., professor of psychiatry, and human and molecular genetics in the Virginia Commonwealth University School of Medicine, and an internationally recognized psychiatric geneticist, said that this is a very large scale study using a new, innovative statistical method.

Kendler asserted that prior to this model, we have not been able to address these questions and their results have given them by far the clearest picture available to date of the degree of genetic similarity between these key psychiatric disorders.

He said that the team is hoping that this will help them both in developing a more scientifically based diagnostic system and understanding the degree of sharing of the biological foundation these illnesses.

The study builds on findings published earlier this year in The Lancet, which reported that specific single nucleotide polymorphisms, or SNPs, are associated with a range of psychiatric disorders that can occur during childhood or adulthood.

The study has been published in Nature Genetics` Advance Online publication.