Amid reports from neighbors and classmates that the gunman in the shooting rampage in, Newtown, Conn., had an autism variant known as Asperger syndrome, adults with the condition and parents of children with the diagnosis are fighting what they fear may be a growing impression that it is associated with premeditated violence.

Individuals with autism spectrum disorders, who are often bullied in school and in the workplace, frequently do suffer from depression, anxiety and suicidal thoughts. A divorce mediator who met with the parents of Adam Lanza, the gunman, during their divorce told The Associated Press that the couple had said that their son’s condition had been diagnosed as Asperger syndrome.

But experts say there is no evidence that they are more likely than any other group to commit violent crimes.

"Aggression in autism spectrum disorders is almost never directed to people outside the family or immediate caregivers, is almost never planned, and almost never involves weapons," said Dr. Catherine Lord, director of the Center for Autism and the Developing Brainat NewYork-Presbyterian hospital. "Each of these aspects of the current case is more common in other populations than autism."

Lord said that in an unpublished review of data tracking several hundred adults with autism over at least the past five years, she and fellow researchers had found no use of weapons. Among more than 1,000 older children and adolescents in that study, only 2 percent were reported by parents to have used an implement aggressively toward a nonfamily member — fewer than in a control group. That finding was repeated in another set of data that she analyzed over the weekend at the request of The New York Times.

But some of the Twitter messages, electronic postings and media reports in the aftermath of the massacre that has horrified the nation have not reflected that characterization of autism.

"Try curing the real disease, Autism, not the N.R.A.," one individual on Twitter wrote Sunday night in response to calls for tighter gun control laws.

"Something’s missing in the brain, the capacity for empathy, for social connection, which leaves the person suffering from this condition prone to serious depression and anxiety," one psychologist said on CNN’s "Piers Morgan Tonight."

In a widely circulated defense of the empathic powers of her 11-year-old son, who has an Asperger diagnosis, Emily Willingham, a science blogger, wrote that "he can’t bear to watch people crack tree nuts, like pecans, because being something of a tree nut himself, he feels pain on behalf of the nuts."

On the DailyKos, a blogger who identified himself as having Asperger syndrome worried that the actions of Lanza, 20, who killed 20 young children and seven adults, including his mother, and was described by a classmate as having a "very flat affect," might be how "people with this disability are defined in the popular imagination."

His own flat affect, he explained,does not mean that he has no feelings.

"Our emotions don’t naturally show on our faces," he wrote. "This is perhaps the most frustrating part of the Asperger experience, because people think you’re not feeling when you may be feeling even more strongly than they are."

The roots of autism, a developmental condition characterized by social impairment, communication difficulty and repetitive patterns of behavior, are not well understood. But it is a problem in processing social information, not an intrinsic inability to empathize, that underlies the condition, experts said.

"The media’s continued mention of a possible diagnosis of Asperger syndrome implies a connection between that and the heinous crime committed by the shooter," said Lori S. Shery, president of the Asperger Syndrome Education Network, an advocacy group in New Jersey. "They may have just as well said, ‘Adam Lanza, age 20, was reported to have had brown hair."’

According to themost recent Centers for Disease Control and Prevention estimate, 1 in 88 U.S. children have an autistic spectrum disorder, whose symptoms range in severity. For a time, it seemed almost faddish to be diagnosed with Asperger syndrome, or high-functioning autism, a condition in which individuals have normal or above-average language skills and intelligence but struggle to observe social rules, like when to make eye contact or to ask a reciprocal question, and to intuit the feelings of others.

Some young adults with the condition proudly branded themselves "Aspies." Temple Grandin, the renowned animal scientist who has the condition, was played by Claire Danes in a 2010 HBO biopic; Craig Newmark, the founder of CraigsList, speculated that he would qualify for the diagnosis; and armchair diagnoses were frequently made of Bill Gates and Sheldon Cooper, the theoretical physicist star of the CBS sitcom "The Big Bang Theory."

The term, saidNew York Magazine in a recent issue, has come to denote anyone who is "some murky hybrid of egghead and aloof."

But if there has been some easing of stigma for people with autism in a world that places a high premium on being socially adept, autism advocates worry that affected individuals may now have another reason to avoid disclosing their condition to teachers, employers and community members — often the first step in raising awareness and obtaining helpful accommodations.

"When I tell someone I’m on the autism spectrum, there’s always a fear that they will judge me in a negative way because of it," said Alex Plank, founder ofWrongPlanet.net, a website where many individuals with Asperger syndrome have poured out their concerns in recent days. "Fortunately, people think ‘Temple Grandin’ or even ‘Bill Gates’ and make a connection in their mind. I’d hate to have someone think ‘Adam Lanza."’

Some of the commenters on Plank’s site reflected an insider’s knowledge of life with an autism spectrum disorder: One wondered why the public school system was not providing Lanza with a "transition to adulthood" program through age 21, as required by federal law.

One young man worried about spending Christmas with distant relatives who might have new prejudices about autism. Others used the outlet to express a sentiment that superseded all others.

"Words cannot express the depth of the pain I feel for those left behind who have to bear this loss," wrote Lee Anderson, 20, of Cookeville, Tenn., whose WrongPlanet profilelists his diagnosis as "Have Aspergers" and his occupation as "Homeschool Student/Paintball Player."

"I wish there was some greater way I could help."

© 2012 The New York Times Company