The DSM is full of curious and non-intuitive disorders like Dissociative Fugue (sudden, unexpected travel away from home, with inability to recall one's past), Voyeurism (recurrent, intense sexually arousing fantasies involving the act of observing an unsuspecting person in the process of disrobing or sexual activity), and Factitious Disorder (intentional production or feigning of physical or psychological signs or symptoms, with external incentives).
Trichotillomania (TTM) is another one. This DSM diagnosis is characterized by repetitive pulling out of one's own hair, accompanied by pleasure, relief, or gratification at the time of pulling, but also usually accompanied by longer term or global distress about the behaviour. This is not the cliched image of the frustrated person pulling out clumps of hair; rather, hairs are selected and plucked one by one from any area of the body, but most often from the scalp, eyebrows, eyelashes, or beard. People with TTM might pull out their hair in front of the bathroom mirror, on the phone, or on the bus; they might use their fingers or a pair of tweezers; they might do it when they are relaxed or when they feel stressed.
Why do people pull out their hair?
In some ways, hair-pulling is a bad habit akin to biting your nails or picking at your skin. You know that pain/relief/pleasure/regret you feel when you pull off a scab or yank out a hangnail? People with TTM will tell you that there's something similarly satisfying about feeling around in your hair until you find a perfect one--usually a hair with a weird colour or texture--and yanking it out of your head. It's rewarding and it feels good to fulfill the urge to pull.
In other ways, TTM is more than just a bad habit. It seems to cause more distress than do nail-biting and skin-picking--significant enough distress to land TTM a spot in the DSM, where it is currently listed as an impulse-control disorder, along with Pyromania, Kleptomania, and Pathological Gambling, among others. In the new version of the DSM (DSM-V, to be published in 2013), TTM will be listed as an Obsessive-Compulsive Spectrum Disorder instead, in recognition of the overwhelming urge that precedes hair-pulling, and the repetitive and compulsive nature of the behaviour.
Some research has found that people with TTM are most likely to pull out their hair when they're bored or during sedentary activities like watching TV or reading, while other research has shown that hair-pulling happens the most when people are anxious, depressed, stressed, or angry. Some research has shown that people with TTM are often perfectionists who have very high standards; when they fail to meet their own elevated standards, they become frustrated and impatient and that's when they pull out their hair. Still other research suggests that there are two types of hair-pulling: one that is habit-like and happens without conscious intent and one where the person with TTM consciously and deliberately grabs the tweezers and heads for the bathroom mirror. None of this research, however, explains why people start pulling out their hair in the first place.
Trichotillomania is not a trivial disorder. A lot of people with TTM feel a great deal of shame, frustration, and distress about their hair-pulling and go to great lengths to hide the behaviour and its consequences--going on pulling sprees when they're home alone, wearing a wig, and avoiding swimming, hairdressers, and windy days. TTM can create relationship issues (e.g., your partner doesn't understand and keeps frustratedly batting your hands away from your hair or demanding that you stop it) and problems at work (you can't focus because your hands drift up to your head every time you sit down at your computer).
If you suffer from TTM, know that there are treatments for this problem. Some are behavioural (i.e., they focus mostly on just plain stopping the behaviour, mostly through increasing awareness of the habit and introducing an alternative habit, kind of like gum chewing instead of smoking), and others focus on mindfully accepting the urge to pull and dealing with the difficult emotions that often precede and follow hair-pulling. These treatments help a lot of people decrease their hair-pulling or stop altogether.