Severe hair-pulling is characteristic of trichotillomania, an impulse control disorder not otherwise classified. Other pathological habits, including severe nail-biting and skin-picking, are also prevalent and are potentially diagnosable as stereotypic movement disorder. There is increasing awareness of the morbidity associated with these kind of habit disorders but, to date, relatively few randomized controlled trials of pharmacotherapy or psychotherapy have been undertaken. Advances in the understanding of the underlying cognitive-affective mechanisms driving stereotypies in animals and humans may ultimately lead to new approaches. An affect regulation, behavioral addiction, and cognitive control (A-B-C) approach is outlined to conceptualizing and managing these conditions.
Kathy is a 38-year-old woman who presented for treatment after reading a newspaper article about research on hair-pulling. She had first begun pulling hairs from her head at 12 years of age. Kathy also pulled hairs from her pubic area. She often chewed her pulled hairs, biting off and swallowing the roots. These were behaviors she was deeply embarrassed about; she had not told her family or sought professional help. The newspaper article had indicated that pubic hair-pulling and trichophagy were quite common. Therefore, Kathy had decided to come in for a psychiatric assessment. As she analyzed her hair-pulling behaviors, it became apparent that these were often precipitated by negative affect, and were positively reinforced by the pleasurable sensation that hair-pulling provided. By using habit reversal techniques, Kathy was able to gradually control her impulses to pull. Over time, her hair began to grow back.
Hair-pulling is precipitated by states of hypoarousal (eg, sedentary activities) and hyperarousal (eg, negative affect).1
There is some evidence that early adversity may contribute toward the pathogenesis of this disorder.2
While the psychobiology of stress is complex, there is certainly data that brain regions involved in mediating the effects of negative emotion and early traumas include the amygdala and hippocampus, and dopaminergic circuits (Figure 1).3
The phenomenology and psychobiology of hair-pulling and other impulse control disorders seem different from that of anxiety disorders in that the former conditions often involve positive reinforcement, while the latter conditions often involve negative reinforcement. Mechanisms involved in positive reinforcement and reward are likely to overlap with those involved in addiction to substances.4
The nucleus accumbens and serotonergic circuits, for example, play a key role in such phenomena (Figure 2).5
Hair-pulling and other kind of motoric habits can also be conceptualized as the inappropriate release of chunks of grooming behavior.6
Hair-pulling and other habits can be performed in a highly automatic fashion,7
and trichotillomania is associated with impaired inhibition of motor responses.8
In animal models, motoric stereotypies are predicted by the extent to which activation in striosomes exceeds activation in the extrastriosomal matrix.9
Such activation could potentially be driven by decreased cortical control or increased striatal activity,10
although other structures, such as the cerebellum, may also play a role (Figure 3).11
These considerations suggest an affect regulation, behavioral addiction, and cognitive control (A-B-C) model of habits. At the same time, there may be considerable overlap in the various mechanisms discussed here. Early adversity and other stressors, for example, result in dopaminergic sensitization12,13
and striatal reorganization.14
There are close links between cortico-striatal circuitry and limbic regions, and amino acids (eg, glutamate) as well as monoamine (eg, serotonin [5-HT], noradrenaline, and dopamine) neurotransmitters are crucial in such circuitry and in habit formation.15-17
Both genes and environments shape habits. Although there is relatively little data on habit disorders, there is some evidence that similar considerations would apply. Thus, pathological grooming behaviors (eg, skin-picking) are more common in familial than sporadic obsessive-compulsive disorder,19
and are more common in relatives of obsessive-compulsive disorder probands than in relatives of controls.20
Particular genes that may play a role in pathological grooming behaviors include 5-HT receptor genes,21 hoxB8
The role of genes, environments, and their interaction is increasingly being delineated in affect regulation. Thus, for example, variation in the 5-HT transporter gene is associated with differential activation to negative, positive, and neutral stimuli in cortical, striatal, and limbic regions (Figure 1).3
Similarly, this genotype contributes to anatomical and functional variation in cingulate-amygdala circuitry, perhaps accounting for some variance in susceptibility to psychopathology.24
Grooming behaviors have been evolutionarily conserved across a range of species.25
Although grooming may serve residual evolutionary functions, excessive grooming in humans can be regarded as pathological due its deleterious effect on quality of life and functioning. The extent to which similar mechanisms are involved across species is unclear, but there is notable overlap in the phenomenology and pharmacotherapy of certain human habit disorders (eg, trichotillomania) and particular grooming disorders in animals (eg, acral lick dermatitis).26-28
In the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition-Text Revision
, trichotillomania is found in the category of impulse control disorders not otherwise classified, while stereotypic movement disorder is found in the category of disorders usually first diagnosed in infancy, childhood, or adolescence. There is no specific diagnostic category for a number of other prevalent habit disorders, including severe skin-picking and nail-biting. These may be diagnosed as impulse control disorders not otherwise specified.
There is a clear argument for including habit disorders, such as trichotillomania and compulsive skin-picking in a section on obsessive-compulsive disorders in a revised nosology.29
There is a lack of clarity about terminology (eg, compulsive skin-picking has also been termed psychogenic or neurotic excoriation), perhaps contributing to lack of awareness despite high prevalence.30-32
There is significant overlap in phenomenology33
and perhaps also in psychobiology across the conditions.34,35
The inclusion of trichotillomania in the official nomenclature and the initial suggestion that it responded selectively to serotonergic agents, encouraged research on the assessment of this disorder. A number of psychometrically sound instruments for its evaluation now exist.36,37
Measures for the assessment of skin-picking severity have also been developed.38
There is, however, significant literature39,40
on the assessment of habits in subjects with intellectual disability exists. Crucial components of the evaluation of habit disorders include the assessment of psychiatric comorbidity, of medical sequelae, of associated shame, and of resulting disability.”41,42
Habit-reversal therapy is the best studied psychotherapy for habit disorders, and selective serotonin reuptake inhibitors are effective in some but not all studies.34,37,43,44
A recent study45
suggests that a combined approach may be particularly useful. An A-B-C model may be used to speculate that some agents improve affect regulation (eg, selective serotonin reuptake inhibitors),44
that others are useful for the component of behavioral addiction (eg, dopamine blockers),45
while a third group may be useful for enhancing cognitive control (eg, topiramate).46
Grooming is an evolutionary conserved behavior that is shaped by genes and environments. In animals, there are increasingly sophisticated studies of the neuronal and molecular basis of motoric habits and stereotypies. In humans, there is growing awareness of the prevalence of abnormal grooming behaviors. More work needs to be done to develop a comprehensive translational understanding of these behaviors, to advance their nosology, and to find effective treatments. In the interim, an A-B-C model, although undoubtedly an over-simplification, may be a useful schema for approaching the habit disorders. Additional randomized controlled trials are needed to develop evidence-based pharmacologic treatment algorithms for trichotillomania and related habit disorders.
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2. Lochner C, du Toit PL, Zungu-Dirwayi N, et al. Childhood trauma in obsessive-compulsive disorder, trichotillomania, and controls. Depress Anxiety
3. Canli T, Omura K, Haas BW, Fallgatter A, Constable RT, Lesch KP. Beyond affect: a role for genetic variation of the serotonin transporter in neural activation during a cognitive attention task. Proc Natl Acad Sci U S A
4. Volkow N, Li TK. The neuroscience of addiction. Nat Neurosci
5. Knutson B, Fong GW, Adams CM, Varner JL, Hommer D. Dissociation of reward anticipation and outcome with event-related fMRI. Neuroreport
6. Graybiel AM. The basal ganglia and chunking of action repertoires. Neurobiol Learn Mem
7. du Toit PL, van Kradenburg J, Niehaus DH, Stein DJ. Characteristics and phenomenology of hair-pulling: an exploration of subtypes. Compr Psychiatry
8. Chamberlain SR, Fineberg NA, Blackwell AD, Robbins TW, Sahakian BJ. Motor inhibition and cognitive flexibility in obsessive-compulsive disorder and trichotillomania. Am J Psychiatry
9. Canales JJ, Graybiel AM. A measure of striatal function predicts motor stereotypy. Nat Neurosci
10. Chamberlain SR, Blackwell AD, Fineberg NA, Robbins TW, Sahakian BJ. The neuropsychology of obsessive compulsive disorder: the importance of failures in cognitive and behavioural inhibition as candidate endophenotypic markers. Neurosci Biobehav Rev
11. Keuthen NJ, Makris N, Schlerf JE, et al. Evidence for reduced cerebellar volumes in trichotillomania. Biol Psychiatry
. 2006 Aug 29; [Epub ahead of print].
12. Thierry AM, Tassin JP, Blanc G, Glowinski J. Selective activation of mesocortical DA system by stress. Nature
13. Matthews K, Robbins TW. Early experience as a determinant of adult behavioural responses to reward: the effects of repeated maternal separation in the rat. Neurosci Biobehav Rev
14. Martin LJ, Spicer DM, Lewis MH, Gluck JP, Cork LC. Social deprivation of infant monkeys alters the chemoarchitecture of the brain: I. Subcortical regions. J Neurosci.
15. Ridley RM. The psychology of perseverative and stereotyped behaviour. Prog Neurobiol
16. Cardinal RN, Winstanley CA, Robbins TW, Everitt BJ. Limbic corticostriatal systems and delayed reinforcement. Ann NY Acad Sci
17. Everitt BJ, Robbins TW. Neural systems of reinforcement for drug addiction: from actions to habits to compulsion. Nat Neurosci
18. Yin HH, Knowlton BJ. The role of the basal ganglia in habit formation. Nat Rev Neurosci
19. Hanna GL, Fischer DJ, Chadha KR, Himle JA, Van Etten M. Familial and sporadic subtypes of early-onset obsessive-compulsive disorder. Biol Psychiatry.
20. Bienvenu OJ, Samuels JF, Riddle MA, et al. The relationship of obsessive-compulsive disorder to possible spectrum disorders: results from a family study. Biol Psychiatry
21. Hemmings SMJ, Kinnear CJ, Lochner C, et al. Genetic correlates in trichotillomania–a case-control association study in the South African Caucasian population. Isr J Psychiatry Relat Sci
22. Greer JM, Capecchi MR. Hoxb8 is required for normal grooming behavior in mice. Neuron
23. Zuchner S, Cuccaro ML, Tran-Viet KN, et al. SLITRK1 mutations in trichotillomania. Mol Psychiatry
24. Pezawas L, Meyer-Lindenberg A, Drabant EM, et al. 5-HTTLPR polymorphism impacts human cingulate-amygdala interactions: a genetic susceptibility mechanism for depression. Nat Neurosci
25. Colbern DL, Twombly DA. ACTH-induced grooming behaviors and body temperature. Temporal effects of neurotensin, naloxone, and haloperidol. Ann N Y Acad Sci.
26. Rapoport JL, Ryland DH, Kriete M. Drug treatment of canine acral lick. Arch Gen Psychiatry
27. Hugo C, Seier J, Mdhluli C, et al. Fluoxetine decreases stereotypic behavior in primates. Prog Neuropsychopharmacol Biol Psychiatry
28. Garner JP, Weisker SM, Dufour B, Mench JA. Barbering (fur and whisker trimming) by laboratory mice as a model of human trichotillomania and obsessive-compulsive spectrum disorders. Comp Med
29. Stein DJ, Simeon D. The nosology of compulsive skin picking. J Clin Psychiatry
30. Woods DW, Miltenberger RG. Are persons with nervous habit nervous? A preliminary examination of habit function in a nonreferred population. J Appl Behav Anal
31. Niehaus CJ, Emsley RA, Brink RA, Stein DJ. Stereotypies: prevalence and association with compulsive and impulsive symptoms in college students. Psychopathology
32. Keuthen NJ, Deckersbach T, Wilhelm S, et al. Repetitive skin-picking in a student population and comparison with a sample of self-injurious skin-pickers. Psychosomatics
33. Lochner C, Simeon D, Niehaus DJH, Stein DJ. Trichotillomania and skin-picking: a phenomenological comparison. Depress Anxiety.
34. Castellanos FX, Ritchie GF, Marsh WL, Rapoport JL. DSM-IV stereotypic movement disorder: persistence of stereotypies of infancy in intellectually normal adolescents and adults. J Clin Psychiatry
35. Simeon D, Stein DJ, Gross S, Islam N, Schmeidler J, Hollander E. A double-blind trial of fluoxetine in pathologic skin picking. J Clin Psychiatry
36. Keuthen NJ, O’Sullivan RL, Ricciardi JN, et al. The Massachusetts General Hospital (MGH) Hairpulling Scale: I. development and factor analyses. Psychother Psychosom
37. Woods DW, Flessner C, Franklin ME, et al. Understanding and treating trichotillomania: what we know and what we don’t know. Psychiatr Clin North Am.
38. Keuthen NJ, Wilhelm S, Deckersbach T, et al. The Skin Picking Scale: scale construction and psychometric analyses. J Psychosom Res
39. Stein DJ, Niehaus DJH, Seedat S, Emsley RA. Phenomenology of stereotypic movement disorder. Psychiatr Ann
40. Jones RSP, Walsh PG, Sturmey P. Stereotyped Movement Disorders
. Chichester, United Kingdom: John Wiley & Sons; 1995.
41. Bouwer C, Stein DJ. Trichobezoars in trichotillomania: case report and literature review. Psychosom Med
42. Woods DW, Flessner CA, Franklin ME, et al. The Trichotillomania Impact Project (TIP): exploring phenomenology, functional impairment, and treatment utilization. J Clin Psychiatry
. In press.
43. O’Sullivan R, Christenson GA, Stein DJ. Pharmacotherapy of trichotillomania. In: Stein DJ, Christenson GA, Hollander E, eds. Trichotillomania
. Washington, DC: American Psychiatric Press; 1999;93-124.
44. Leonard HL, Lenane MC, Swedo SE, Rettew DC, Rapoport JL. A double-blind comparison of clomipramine and desipramine treatment of severe onychophagia (nail biting). Arch Gen Psychiatry
45. Stein DJ, Hollander E. Low-dose pimozide augmentation of serotonin reuptake blockers in the treatment of trichotillomania. J Clin Psychiatry
46. Lochner C, Seedat S, Niehaus DJH, Stein DJ. Topiramate in the treatment of trichotillomania: an open-label pilot study. Int Clin Psychopharmacol
Dr. Stein is professor and chair of the department of mental health and psychiatry at the University of Cape Town in South Africa, and is also on faculty at Mount Sinai School of Medicine in New York City. Mr. Chamberlain is researcher in the department of psychiatry and a student doctor on the Cambridge MB/PhD programme at the University of Cambridge in the United Kingdom. Dr. Fineberg is professor of psychiatry at the University of Hertfordshire in the United Kingdom.
Disclosures: Dr. Stein receives grant support/honoraria from AstraZeneca, Eli Lilly, GlaxoSmithKline, Lundbeck A/S, Orion, Pfizer, Pharmacia, Roche, Servier, Solvay, Sumitomo, and Wyeth. Mr. Chamberlain does not have an affiliation with or financial interest in any organization that might pose a conflict of interest. Dr. Fineberg receives grant support from GlaxoSmithKline, is a consultant to AstraZeneca, Lundbeck A/S, and Wyeth, and is on the speaker’s bureaus of Bristol-Myers Squibb, GlaxoSmithKline, and Lundbeck A/S.
Funding/Support: Dr. Stein receives support from the Medical Research Council of South Africa.
Authors’ note: This case is based on an amalgam of the authors’ experience.