A study involving 116 chimpanzees that were used in medical testing revealed 95 percent of them showed behavioral signs similar to those of humans who have post-traumatic stress disorder, the Independent reported Saturday.
The Independent said workers at a Louisiana animal center were questioned about chimps' behavior in the survey.
The study, which will be presented Monday at a primate conference in Edinburgh, Scotland, will be part of an effort to outlaw subjecting great apes to medical testing in Europe, the report said.
"There are obvious differences between species but it's obvious that these chimps are suffering chronically," Dr. Hope Ferdowsian, director of research policy for the Physicians Committee for Responsible Medicine, said. "The patterns of behavior we are seeing in these chimps are not normal and not seen in the wild."