Volkmar said the study is consistent with a prevailing theory that genes are a cause of autism, but he said the results need to be tested to prove the fathers' age was a culprit. For example, the study lacked information on whether the fathers themselves had autism.

Autism is a developmental disorder that involves an impaired ability to socialize and communicate. Symptoms can include repetitive behaviors such as head-banging; avoidance of physical or eye contact with others, and communicating with gestures rather than words. It is more common in boys than in girls and typically is diagnosed in the first few years of life.

Many researchers believe impaired genes are a cause or trigger of autism. Most studies have failed to find evidence to support a persistent belief among some parents that mercury-containing childhood vaccines are to blame.

---

On the Net:

www.archgenpsychiatry.com

National Institutes of Health:

www.nichd.nih.gov/