Nov. 19 (HealthDay News) -- A large, five-year study looking at the genetic and environmental factors that may cause autism, as well as other developmental delays, has started enrolling 2,700 children and their families from six areas in the United States.

The Study to Explore Early Development -- which researchers called the largest of its kind -- will include children with autism and other developmental delays, as well as children with normal development.

Family medical history, genetics, and sociodemographic, lifestyle and environmental factors will be among the areas of focus in the study. Information will be gathered through interviews, physical examinations, medical records and cheek swab, blood and hair samples.

"We hope this will help us learn more about the factors that may lead to autism and other developmental disabilities, and how genes and the environment may affect child development," Lisa A. Croen, principal investigator at a site in California, said in a prepared statement.

"The results may also contribute to better services and treatments for affected children and to prevention strategies," said Croen, an epidemiologist with Kaiser Permanente's Division of Research in Oakland, Calif.

It's not understood why, but the incidence of autism is increasing and now affects about one in 150 children born in the U.S. The chronic disorder affects the normal functioning of the brain and affects development of communication and social skills.

SOURCE: Kaiser Permanente, news release, Nov. 14, 2007