"A person may want to get even for some loss. He or she may blame the disabled person for some personal miseries, such as getting passed over for a job."
"Since the ADA was enacted, those who have disabilties are seen as costing us a lot of money," Levin added. "Many Americans see them as a threat to their economic well-being."
And people may simply be motivated by the thrill of killing and see the disabled as easy targets, Levin said.
Experts have different opinions on the best ways to address the problem, but they do agree that a solution will not be easy to come by.
While the study identifies a trend of abuse against people with disabilities, more research is needed to determine the cause-and-effect relationship.
"It's not yet clear whether violence comes first, or the disability in some cases," said Sobsey. "Violence is a major cause of psychiatric symptoms and disabilities."
In an accompanying editorial, Esme Fuller-Thomson and Sarah Brennenstuhl of the University of Toronto wrote that health care providers need better tools to screen for and identify violence among their patients.
"In addition to improved identification of victims is the need for appropriate care and support services," they wrote.
Levin believes that the first step should be better recognition of the violence against the disabled.
"We don't need any more laws," he said. "We need to change the thinking of ordinary Americans who are unaware that people with disabilities are being targeted. If Americans recognized the harm that was being done, they might be more likely to intervene."
The Associated Press contributed to this report.