Stress, stereotypies and welfare.

Stereotypies have been attributed various functions ranging from coping with conflict and frustration to self narcotization via activation of endogenous opioids. However, the evidence in favor of these postulated functions is far from conclusive. Stereotypies are more likely to represent the outward expression of disturbances in brain neural structures controlling persistence of behaviour in response to environmental precipitating factors interacting with individual predisposing factors.