Trichotillomania, the compulsive urge to pull out one’s own hair, is recognised as a disorder leading to noticeable hair loss, distress, and social or functional impairment. It is often chronic and difficult to treat.
Trichotillomania may be present in infants, but the peak age of onset is 9 to 13. It may be triggered by depression or stress. Due to social implications the disorder is often unreported and it is difficult to accurately predict its prevalence; the lifetime prevalence is estimated to be between 0.6% (overall) and may be as high as 1.5% (in males) to 3.4% (in females).
The name, coined by French dermatologist François Henri Hallopeau, derives from the Greek: trich- (hair), till(en) (to pull), and mania (“an abnormal love for a specific object, place, or action”).
Trichotillomania is usually confined to one or two sites, but can involve multiple sites. The scalp is the most common pulling site, followed by the eyebrows, eyelashes, face, arms, legs, and pubic hairs. The classic presentation is the “Friar Tuck” form of vertex and crown alopecia. Children are less likely to pull from areas other than the scalp.
Individuals with trichotillomania exhibit hair of differing lengths; some are broken hairs with blunt ends, some new growth with tapered ends, some broken mid-shaft, or some uneven stubble. Scaling on the scalp is not present, overall hair density is normal, and a hair pull test is negative (the hair does not pull out easily). Hair is often pulled out leaving an unusual shape; individuals with trichotillomania may be secretive or shameful of the hair pulling behavior.
An additional psychological effect can be low self-esteem, often associated with being shunned by peers and the fear of socializing due to appearance and negative attention they may receive. Some people with TTM wear hats, wigs, wear false eyelashes, eyebrow pencil, or style their hair in an effort to avoid such attention. There seems to be a strong stress-related component. In low-stress environments, some exhibit no symptoms (known as “pulling”) whatsoever. This “pulling” often resumes upon leaving this environment. Some individuals with TTM may feel they are the only person with this problem due to low rates of reporting.
-Content from http://en.wikipedia.org/wiki/Trichotillomania