While an official has said that the 20-year-old gunman in the Connecticut school shooting had Asperger's syndrome, experts say there is no connection between the disorder and violence.
Asperger's is a mild form of autism often characterized by social awkwardness.
"There really is no clear association between Asperger's and violent behavior," said psychologist Elizabeth Laugeson, an assistant clinical professor at the University of California, Los Angeles.
Little is known about Adam Lanza, identified by police as the shooter in the Friday massacre at a Newtown, Conn., elementary school. He fatally shot his mother before going to the school and killing 20 young children, six adults and himself, authorities said.
A law enforcement official, speaking on condition of anonymity because the person was not authorized to discuss the unfolding investigation, said Lanza had been diagnosed with Asperger's.
High school classmates and others have described him as bright but painfully shy, anxious and a loner. Those kinds of symptoms are consistent with Asperger's, said psychologist Eric Butter of Nationwide Children's Hospital in Columbus, Ohio, who treats autism, including Asperger's, but has no knowledge of Lanza's case.
Research suggests people with autism do have a higher rate of aggressive behavior — outbursts, shoving or pushing or angry shouting — than the general population, he said.
"But we are not talking about the kind of planned and intentional type of violence we have seen at Newtown," he said in an email.
"These types of tragedies have occurred at the hands of individuals with many different types of personalities and psychological profiles," he added.
Autism is a developmental disorder that can range from mild to severe. Asperger's generally is thought of as a mild form. Both autism and Asperger's can be characterized by poor social skills, repetitive behavior or interests and problems communicating. Unlike classic autism, Asperger's does not typically involve delays in mental development or speech.
Experts say those with autism and related disorders are sometimes diagnosed with other mental health problems, such as depression, anxiety, bipolar disorder or obsessive-compulsive disorder.
"I think it's far more likely that what happened may have more to do with some other kind of mental health condition like depression or anxiety rather than Asperger's," Laugeson said.
She said those with Asperger's tend to focus on rules and be very law-abiding.
"There's something more to this," she said. "We just don't know what that is yet."
After much debate, the term Asperger's is being dropped from the diagnostic manual used by the nation's psychiatrists. In changes approved earlier this month, Asperger's will be incorporated under the umbrella term "autism spectrum disorder" for all the ranges of autism.
AP Writer Matt Apuzzo contributed to this report.