Human Illnesses, including Autism, Attention Deficit Disorder, Bipolar Disease, Schizophrenia and Major Depression, Linked to Common DNA Roots

A new study confirms that the five most common mental illnesses-autism, attention deficit disorder, bipolar disease, schizophrenia and major depression-all have a common genetic link.

"We have been able to discover specific genetic variants that seem to overlap among disorders that we think of as very clinically different," Dr. Jordan Smoller of Massachusetts General Hospital in Boston, who led the study, said in a telephone interview.

The finding, published in the journal The Lancet on Wednesday, may eventually lead to a complete rewrite of the medical understanding of the causes of mental illness, according to NBCNews.com .

 "We think this is one tiny fraction of the genetic component of these disorders. They involve hundreds and possibly thousands of genes," Smoller said.

However, researchers point out that this is just a jumping off point of many psychological problems and does not explain all mental health conditions.

Smoller's team, a compilation of researchers who looked at the genetics of more than 33,000 psychiatric patients and compared them to nearly 28,000 people without mental illness, scanned their DNA in a genome-wide association study.

Researchers linked a considered number to four places in the genome, which was not a complete surprise as they have noted the overlapping of many symptoms previously. "Autism was once known as childhood schizophrenia and the two disorders were not clearly differentiated until the 1970s," the team wrote.

Researchers are hoping that this will lead to better treatments."We are finally starting to make inroads where we have actual physiological mechanisms that we can target," Dr. Bruce Cuthbert, who is director of the National Institute of Mental Health's division of Adult Translational Research. "We can really start to understand the biology instead of having to guess at it."