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).

There are some indications that TTM/HP may be genetically associated with OCD (10,22,28) though the evidence gives mixed results. In an uncontrolled observational cohort study, 15% of 60 adults with TTM/HP interviewed by Christenson and coworkers (17) reported lifetime histories of OCD. Lenane and coworkers (28) interviewed 65 of 69 first degree relatives of 16 girls with OCD and similar number of parents of healthy volunteer control group. Three of 16 (19%) girls with TTM had a first-degree relative with a lifetime history of OCD, and there was overall a 6.4% lifetime prevalence rate of OCD in the first-degree relatives of girls with TTM. King and coworkers (10) described 15 clinic-referred children with TTM/HP who were assessed for comorbid diagnoses and whose parents were also assessed for lifetime histories of tics and OCD. Seven participants had comorbid disruptive behavior disorders, three had a current or past history of chronic motor tics and three had comorbid anxiety disorders. Only two participants had OCD. For the family study, 11 participants had both parents interviewed and four had only one parent directly interviewed; one participant was adopted and another was in the care of his/her father and stepmother. Among the parents, two met criteria for OCD and six had OC symptoms that were subthreshold. Two fathers had Tourette disorder and one had chronic multiple tic disorder. In contrast, a controlled family study of 88 adults with rigorously diagnosed OCD and 343 of their first degree relatives was conducted by Bienvenu and coworkers (22). Individuals were included if they has YBOCS severity scores greater than 15, and individuals with Tourette disorder were excluded. Among probands, 4% had current or past histories of TTM, but this was not statistically significant in comparison to controls, where one case was identified. Similarly, two cases (1%) of first degree relatives gave a history for TTM and this was not statistically different from controls. The scope of the Bienvenu and coworkers (22) study was wider than just TTM and included other “pathological grooming behaviors” such as pathological skin picking and nail biting. When probands were compared to healthy volunteers, the rate for TTM was not elevated, but the rates for the other pathological grooming behaviors were (25% for nail picking and 24% for skin picking, compared to 14% and 6% respectively in healthy volunteers). However, only skin picking was statistically significantly greater, and rates for all grooming behaviors were not elevated in first-degree relatives of OCD patients compared to relatives of controls (22).