A comparison of women with TTM and with OCD found significant differences in clinical variables; OCD patients had more comorbidity, greater disability, increased childhood interpersonal trauma (specifically sexual abuse) and more maladaptive schemas. Fewer TTM patients, however, reported having responded to treatment.
The gender ratio findings in both OCD and TTM groups were similar to other surveys where a mean female:male ratio of 1.5:1.0 in OCD [11,32,33] and approaching 10:1 in TTM [34] were documented. OCD patients' mean total score on the YBOCS (i.e. 20.1 ± 8.0) puts them in the "moderate" severity category [22]. The mean hair-pulling severity score on the MGHHPS (16.1 ± 6.5) was similar to that reported in other studies [35,36]. Taken together, these data suggest that our patients are not dissimilar from those assessed at other sites.
Our comorbidity findings are consistent with existing data suggesting that depressive and anxiety disorders are highly prevalent in both OCD and TTM, and significantly more prevalent in OCD [3,16,18]. Indeed, compared to TTM, comorbidity in OCD is greater across a range of different diagnostic categories including mood (MDD, dysthymia), anxiety (panic disorder), OCD-related (hypochondriasis) and personality disorders (OCPD). Such comorbidity appears to extend also to impulse control disorders (intermittent explosive disorder), a finding which argues against the current classification of trichotillomania as a member of this spectrum of conditions.
Our findings of increased disability in OCD is consistent with studies on OCD suggesting it is one of the most impairing of all medical disorders [37]. A number of clinical studies have emphasized the burden of OCD across different domains, including higher rates of divorce and separation than in subjects without OCD [13] and significantly impaired instrumental functioning (work, school, home making and family life) [38-41]. However, the impairment and distress due to TTM should not be underestimated: TTM can be associated with serious sociological and psychological effects (e.g. strong feelings of shame and embarrassment [42], as well as avoidance behaviour including potentially dangerous avoidance of medical care [43]) resulting in a significant decline in quality of life (QOL) for patients, their family members and significant others [44,45].
OCD patients reported significantly more sexual abuse than TTM patients (p = .04). This finding differs from our previous data suggesting similar rates of childhood interpersonal trauma (CIT) in OCD and TTM [46]. However, the current sample size is much increased, resulting in more power to detect smaller differences. Indeed, increased rates of OCD (and other anxiety disorders) have previously been linked with a history of physical and sexual abuse during childhood [47,48]. Nevertheless, in both OCD and TTM, dissociative symptoms – which are present in a minority of patients in both conditions – are positively correlated with a history of childhood interpersonal trauma [49], so that a potential role for CIT in some TTM patients should not be ignored [50].
TTM patients had significantly more novelty seeking (NS) than OCD patients, whereas OCD patients scored significantly higher on harm avoidance (HA) compared to TTM. Our findings are consistent with previous work on temperament / character in OCD, showing increased HA and decreased NS [51-53]. Of note, compared with mean temperament scores obtained in a normal community sample [30], both TTM and OCD scored high on HA. NS scores in the TTM sample were higher than in the OCD sample, but compared to normal controls, these fell in the "medium" range. The higher NS in TTM may however point to greater dopaminergic involvement in this disorder, and might also be used to argue that TTM lies closer to the more impulsive risk-/novelty-seeking pole of an impulsive-compulsive (IC) spectrum of disorders [54].
OCD patients had more maladaptive cognitive schemas than TTM, i.e. mistrust / abuse, social isolation, shame / defectiveness, subjugation and emotional inhibition. The schemas that OCD and TTM patients differed on are included in 2 of the 4 higher order factors (i.e. "impaired autonomy" and "disconnection") described by Lee and colleagues' YSQ factor model [55]. While schemas are thought to represent responses to life experience, including the experience of a disorder, they may also reflect underlying symptoms. Given that maladaptive schemas in OCD were not reminiscent of its characteristic symptoms, it is likely that they at least partly reflect life experience. An increased number of maladaptive schemas in OCD is consistent with higher rates of comorbidity, disability, and functional impairment. Nevertheless, further empirical investigation is needed to assess the relationship between schemas and illness course.
Hormonal influences have previously been investigated in OCD [56] and TTM [57]. For example, it has been noted that menarche, premenstruum, pregnancy [58], and menopause [59] may be related to onset or relapse in OCD. Similarly, in a study that investigated the relationship of the menstrual cycle and pregnancy to compulsive hair-pulling, premenstrual symptom exacerbation was reported for actual hair-pulling, urge intensity and frequency, and ability to control pulling [57]. In that study the impact of pregnancy on TTM was less clear. Our findings suggest that significantly more OCD patients than TTM patients report an association between pregnancy/puerperium and the onset of illness. This finding is in part consistent with previous work suggesting that the postpartum may constitute a risk for the onset of OCD in women [60]. Taken together our data suggest both similarities and differences in the role of sexual hormones in the mediation of OCD and TTM.
Although rare, brain injury may play a role in some cases of OCD [61,62]; in only one OCD patient (and none of the TTM patients), head injury was associated with onset of obsessive-compulsive symptoms. No data could be found on the potential role of brain injury in the etiology of hair-pulling.
A number of patients associated the onset of their OCD onset with an infection, possibly bacterial pharyngitis. This finding is consistent with a body of data suggesting post-streptococcal disease is a cause of OCD in children and adolescents [63], and perhaps also adults [64,65]. There is less work demonstrating a role for autoimmune factors in TTM [66]. Notably, the data on bacterial pharyngitis were based on retrospective assessment and could have been contaminated by memory bias.
In our study, more OCD patients reported a positive response to treatment (with CBT or SRI's) than TTM patients. These data should be interpreted cautiously given the retrospective assessments. Nevertheless, there is evidence that SRI's in TTM may not be as effective over the long-term as in OCD [2]. About 40–60% of OCD patients respond to the first trial of an SRI [67], with a proportion of non-responders to a single SRI responding to administration of a second SRI [68]. In comparison, it has been suggested that TTM patients judge their treatment (including pharmacotherapy, psychotherapy, and behaviour modification) to be relatively ineffective [69]. The usefulness of SRI's in TTM has been investigated in a number of studies with results so far being equivocal. For example, Christenson et al [70] were unable to document efficacy for fluoxetine in a placebo-controlled trial in which patients received 6 weeks of the active agent in doses of up to 80 mg/day. Anecdotal evidence also suggests that the effectiveness of SRI's in TTM may wane with time [71].
Although there is evidence for the usefulness of behaviour therapy in both OCD [72] and TTM [73], the focus of the treatment differs in the two disorders (exposure and response prevention in OCD versus habit reversal in TTM). Keuthen et al [74] have suggested that "state-of-the-art" behavioral and pharmacological treatments offer substantial clinical benefit to patients with TTM, but in general clinics there may be relatively little experience with highly specialized interventions.
Several limitations of the current study should be acknowledged. First, interviewers were not blind to the patients' psychiatric diagnosis, so potentially biasing clinician's assessments. Nevertheless, a structured diagnostic instrument ensures a reasonable degree of reliability. Second, instruments employed in the current study are intended for use in adults rather than younger subjects. However, in the case of children and adolescents, the SCID-I was supplemented with a clinical interview of parents or guardians, and self-report data was included only when it was clear that questionnaires had been completed meaningfully. Third, source of referral, and the duration of OCD/TTM, were not controlled for in the analysis, so potentially biasing the analyses. However, given the chronicity of both conditions, this is unlikely to have materially affected the findings. Fourth, males, as well as patients with comorbid OCD and TTM were excluded from the investigation; so that the results here may not be generalizable to all OCD or TTM subjects. Given evidence that the phenotype of OCD [75] and of TTM [10] varies with gender, additional work on male subjects should be undertaken in the future.
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