Hair pulling: a review.

Hair pulling has been reported in humans, six different non-human primate species, mice, guineapigs, rabbits, sheep and muskox, dogs and cats. This behaviour seems to occur only in subjects who are confined in an artificial environment. It has been classified as a mental disorder in humans, as a behavioural pathology in animals. The hair is not only pulled but also, in most species, ingested. Hair pulling can be both self-directed and partner-directed, contains elements of aggression, manifests more often in females than in males, is associated with psychogenic distress, and resists treatment. Research data collected from affected animals are probably not normative, hence scientifically unreliable. The preemptive correction of husbandry deficiencies causing long-term stress may prevent the development of this bizarre behaviour in healthy subjects.