Autism, schizophrenia and manic-depressive disorder may be linked to several of the same genes, scientists said in a study that may spark a search to identity such genes as a prelude to seeking new treatments.

About 20 percent to 60 percent of gene variants that raise people's risk of autism, a mysterious brain disorder, also increase vulnerability to manic-depressive illness, according to the study, released today. Autism risk may be linked just as closely to schizophrenia, said the authors, led by Andrey Rzhestky, a University of Chicago computational biologist.

The findings, to be published this week in the Proceedings of the National Academy of Sciences, come from a statistical analysis of the symptoms and characteristics of 1.5 million patients with 161 diseases. The study may also guide researchers who are trying to find the underpinnings of conditions such as diabetes, heart disease and Alzheimer's disease.

"We're currently throwing out a lot of information in our genetic studies because it's not related to the specific disease we're interested in," Rzhetsky said today in a telephone interview. "By studying the interrelatedness of disease, we can use more of that information and get more precise information about the genetic variations associated with diseases."

Rzhetsky said other researchers have expressed interest in "using the approach to help them" look for genes linked to diseases.

The study also showed that the nerve diseases are often related to illnesses in which the immune system attacks the patients' organs, such as diabetes and psoriasis. Certain infectious diseases, such as viral encephalitis, tuberculosis, and infection from staph bacteria, also appeared to be linked to the nervous-system disorders, Rzhestky said.

"The presence of these autoimmune disorders and infectious diseases may be relevant," he said. "By looking at them jointly, we may be able to get more information from the same set of observations or patient records."