Franciose Henri Hallopeau coined trichotillomania (TTM) from the Greek words for “hair + pulling + madness” in 1889 (1,2). TTM and OCD share an obvious similarity of repetitive behavior and this has led some investigators to consider whether there is more than a surface relationship between them (3,4,5,6). Some have proposed that both are part of a larger obsessive-compulsive spectrum disorder (4,7). The concept of an obsessive-compulsive spectrum disorder draws on shared characteristics of impulsive and repetitive behaviors and encompasses a wide range of conditions— obsessive-compulsive disorder, all impulse control disorders (kleptomania, pyromania, trichotillomania, intermittent explosive disorder), all the paraphilias, sexual and gambling addictions, autism, Tourette disorder, and all the DSM Cluster B (antisocial, borderline, narcissistic, histrionic) personality disorders (4,7). The merits and problems of an obsessive-compulsive spectrum disorder are beyond the scope of this chapter, but the association of TTM and OCD demand that one considers whether it is appropriate to place them together and appreciates their similarities and dissimilarities. This is especially the case for child psychiatry, since there is evidence to suggest that childhood-onset OCD is a risk factor for TTM (8,9) and that TTM often has its onset in childhood and adolescence (8,9,10,11).

The formal diagnosis of TTM in DSM-IV-TR (12) requires both behavioral and psychological components— hair pulling to the point of conspicuous hair loss accompanied by rising tension prior to hair pulling and gratification during or after it. Some investigators consider the DSM criteria to be excessively restrictive (10,13,14,15,16). The prevalence of hair pulling (HP) without psychological components is nearly 4% in the general population (13,15), compared to the 0.6–1% prevalence reported for TTM (13,15). Generally females are more common in clinical samples. The age of onset is bimodal, with incident peaks in early childhood and adolescence. Forty-five to 55% of TTM/HP patients report a childhood (before age 18) onset (17). Demonstrating that HP shows a similar course, prognosis, genetic risk, and treatment response to TTM convincingly would establish that they have a close relationship.

It appears that TTM and HP are often comorbid with OCD (15,18,19). Four to 35% of patients with OCD report lifetime histories of TTM/HP (16,19,20,21,22), while 13–16% of those with TTM/HP report lifetime histories of OCD (17,23,24). TTM and HP also are commonly associated with tic
disorders (8,10,19,21,22,25). As with tics, TTM/HP appears to be particularly associated with early-onset OCD (10,19,21). TTM/HP are also associated with hoarding (26). Most studies have relied exclusively on clinical populations at risk, producing an erroneous, biased association (27). However, two studies drawing on nonreferred, more epidemiological populations suggest an association may in fact exist (13,15).