The evolved behaviors that humans engage in to avoid contact with infectious diseases could help explain pervasive stigma……
“In response to the recurrent threat of infectious disease, a variety of species appear to have evolved behavioral adaptations to counter pathogen threat…Among humans, [and proto humans] it is believed that infectious disease was perhaps the single greatest contributor to morbidity and mortality ancestrally. In response, there exists a behavioral immune system – a psychological system designed to promote the avoidance of potential pathogen carriers.”
Animals, including humans, tend to over perceive disease cues and frequently commit false-positive errors….it is better to accidentally avoid someone who isn’t diseased than accidentally approach someone who is. This heightened sensitivity to disease threats “has been used to explain prejudice towards immigrants and foreigners, the physically disabled, the elderly, and the obese,”
“Given the physiological and behavioral similarities between normal immune responses and mental disorders, it is plausible that an oversensitive behavioral immune system would misperceive mental illness cues as physical illness,”
…people were more likely to associate mental illness with sickness than with aggressive behavior or danger. The association between mental illness and disease was strengthened among those who had recently been sick and those who had been warned about a recent epidemic disease threat.
“The present findings suggest that the stigma against the mentally ill is due, in part, to people associating mental illness with disease cues…”