While more and more Americans regard mental illness as a disease rooted in the brain, that doesn't mean they are getting more tolerant of those who suffer from it.

That's according to a new report comparing national surveys from 1996 and 2006.

In recent decades, both the government and the medical community have tried to reduce the social stigma shrouding psychiatric conditions like schizophrenia and depression -- in large part by stressing their biological underpinnings.

But those efforts appear to have failed, according to the new findings in the American Journal of Psychiatry.

"Americans continue to get more sophisticated in their understandings of what causes mental illness," said Bernice A. Pescosolido, who led the new research.

"But that did not translate into greater tolerance," Pescosolido, a sociologist at Indiana University in Bloomington, said in an e-mail to Reuters Health. "In fact, in some cases, it looked like it backfires."

She and her colleagues tapped into data from nearly 2,000 Americans, who had been interviewed about their attitudes toward mental illness as part of the General Social Survey conducted every two years by University of Chicago researchers.

From 1996 to 2006, the number of people who thought depression was rooted in brain biology climbed from just over half to nearly two-thirds; for schizophrenia, the number rose from 76 to 86 percent.

Most people also thought these illnesses should be treated by a doctor and with prescription medicine. However, in the case of drinking, two-thirds of people chalked the problem up to "bad character" in 2006, up from half in 1996.

There was little change in social stigma. For example, most people said they wouldn't want a person with schizophrenia or depression to marry into their family.

"People with mental illness often face rejection -- in friendships, in jobs, and in family situations," Pescosolido said.

While the reasons aren't clear, a scientific understanding didn't appear to help.

"If people think it is biological or genetic, they are seeing people in a different 'class' and with some permanence that could impact their 'family line,'" Pescosolido told Reuters Health.

"We need to think about new ways to think about 'difference' and tolerance," she added. "The focus should not be on 'disease like any other' but competencies and community integration, the fact that 'everybody has something' that they live with and have successful lives."