Obsessive-Compulsive and Related Disorders

Case: Nadia, 14. Five chapters follow: the case, epidemiology, presentation, functional neuroscience, and treatment.

The case: Nadia, 14

Nadia is fourteen and in ninth grade. Her pediatric dermatologist refers her with this note: "Six-month history of patchy hair loss at the vertex and left frontal scalp. Hairs broken at differing lengths, no scale, no exclamation-point hairs, pull test negative. Findings are consistent with hair pulling rather than alopecia areata or tinea. Mother also reports very long periods at the mirror and a recent request for a procedure on her nose. Please assess for trichotillomania and for body image concern."

Nadia's own account begins with her hand rather than a decision. "I don't decide to do it. I look down and there's hair on the keyboard." That happens during homework, while scrolling, and during silent reading, usually with her left hand at the crown. She describes a second kind of pulling differently. In the bathroom, with the door locked, she runs her fingertips over the scalp to find hairs that "feel wrong, thick or kinked," and pulls those one at a time. Before she finds one there is a tightness "in my hands and behind my eyes"; after the pull, "it's done, for a second." She examines the root, sometimes bites it off, and drops the hair in the sink. She has never swallowed hair. Over the past two months she has also begun pulling her lower eyelashes.

The mirror comes up when she is asked about mornings. Part of the time she is arranging her hair to cover the patch and deciding whether the headband is enough. She estimates this at ten minutes and says it is "so nobody asks." The rest of the time, often thirty minutes or more, is spent close to the glass looking at the pores on her nose, which she describes as "huge, obviously, everyone can see them." When told that neither the dermatologist nor the interviewer sees anything unusual, she says people are being polite. She asked her mother last month whether laser treatment "fixes noses." She has photographed her nose in different lighting and deleted most of the pictures.

Nadia was born at term and met milestones on time. She was a shy child who worried about her mother leaving at kindergarten drop-off for one school year, then settled. She reads well and is on the honor roll. The pulling began in the spring of eighth grade, after a haircut she disliked and during the weeks before final exams. Her mother bites her nails and describes herself as "a worrier." Her father's brother was treated for obsessive-compulsive disorder in his twenties. Her maternal grandmother's house has two rooms that cannot be entered because of accumulated newspapers, fabric, and containers. Nadia's mother says she "has a bit of that too," and regularly clears Nadia's room of hair ties, cosmetic samples, and craft packaging that Nadia protests she was keeping "for something."

In session, Nadia wears a wide headband and makes easy eye contact. When the conversation turns to school she runs her fingers along the hairline and twirls a strand around her index finger without pulling. When the patch is mentioned directly she covers it with her palm and does not remove her hand for several minutes. She answers questions about the pores by turning her head to show her profile. She says the pulling is "my own hand, obviously," but the pores are "a fact." Asked what she wants, she says she wants the hair back and wants to swim with her friends in June without a cap.

Her mother adds that she finds hairs on the desk most evenings and in the sink each morning, that Nadia becomes angry when hurried away from the mirror, and that mornings have made her late for school four times this month. Nadia's mood has been lower for about two months. She has withdrawn from a swim team she liked and says she is "disgusting to look at." She denies thoughts of harming herself. Her homeroom teacher describes an attentive, capable student who sits with one hand at her head during independent work and who was excused from swimming in physical education at her mother's request.

Epidemiology

The reference list for this module concentrates on three related disorders rather than on OCD itself, and this chapter follows the list: trichotillomania, body dysmorphic disorder and hoarding disorder. No community prevalence for pediatric OCD is in the list, and none is given here.

Trichotillomania

Community studies suggest that trichotillomania affects between 0.5% and 2.0% of the population [28]. An imaging paper's introduction gives a lifetime prevalence of approximately 0.5% to 1% with a peak age of onset in adolescence, at 12 to 13 years [21]. A clinical reference reports a lifetime prevalence beginning in adolescence "as high as 3.5%," with the caveat that not all such adolescents meet full criteria, and a female-to-male ratio of about 9:1 with underreporting attributed to stigma [29]. Adult clinical samples reflect that imbalance: 92.1% of the 76 patients in the multi-site imaging analysis were female [21].

Younger children look different. In a retrospective series of 33 children with trichotillomania at a tertiary children's hospital, 28 were girls and 5 boys, the peak age was 3 to 4 years, the scalp was the most common site, and only 51.5% of parents had noticed the hair-pulling [31]. Triggers were identified in 16 children, including appearance, family, school and concurrent illness, and loss to follow-up was high [31]. Nadia, at 14 with a dermatology referral, is in the adolescent peak; the early-childhood form, with a prognosis described as better the younger the age of occurrence, is a different population and a different prognosis [29].

The reviews on assessment and management note the paucity of psychopathology and treatment research in pediatric populations [30]. Neuropsychological and neuroimaging findings across 30 primary studies (591 participants with trichotillomania) show group differences with effect sizes of 0.25 to 1.58 where significant, from heterogeneous methods that the reviewers call tentative [20]. The management review in the list could not be retrieved [22].

Body dysmorphic disorder

Body dysmorphic disorder is estimated to affect around 2% of young people and typically emerges during adolescence [23, 24]. Only about 15% of individuals with the disorder are actually diagnosed with it [23]. A pediatric clinical series of 172 youths aged 10 to 19 (mean 15.6) from specialist clinics in Stockholm and London, reported 136 girls, 32 boys and 4 transgender youths, a self-reported mean onset at 12.6 years (SD 2.4, range 4 to 17), current comorbidity in 71.5% (major depression or dysthymia 46.5%, social phobia 10.5%), suicidal ideation in 58.6%, self-harm in 52.1%, suicide attempts in 11.0%, a desire for cosmetic procedures in 53.7% (9.8% already received), and complete school dropout in 32.4% [24]. Girls had more severe symptoms, depression, suicidality and self-harm, with any suicidal or self-harm behavior in 73.3% versus 40.0% of boys [24]. A commentary on the field cites similar figures across the literature: suicidal ideation up to 80%, attempts 40%, self-harm up to 52%, substance misuse 44%, and about a third dropping out of school [23]. These are referred-clinic samples; the community rate is the 2% figure, and the impairment figures describe those who reach specialist care. In two retrospective clinical samples, the mean age at onset of body dysmorphic disorder was 16.7 years, and about two thirds (66.3% and 67.2%) reported onset before 18 [25]; those are referred adults recalling onset, not incidence figures.

Hoarding disorder

Hoarding disorder in youth is rare by strict criteria and more common as a behavior. In a two-stage Turkish study, 3,249 schoolchildren were screened with a parent-rated inventory and 318 with hoarding behavior were interviewed; 32 met criteria, an estimated prevalence of 0.98% (95% CI 0.7–1.4), with a female-to-male ratio of 3:1 and comorbid psychiatric disorder in 56.2% [27]. A Swedish twin-cohort follow-up illustrates the gap between screen and diagnosis: 2% of adolescents screened positive at 15, but at clinical interview a median of three years later none had clinically significant clutter and therefore none met strict DSM-5 hoarding disorder, while 28 met partial criteria and had more psychiatric disorders than their co-twins (any disorder 78.6%, current anxiety 53.6%, past major depression 50.0%), predominantly girls; the authors conclude that hoarding disorder as defined in DSM-5 "may be rare in young people" [26].

A shared liability

Twin modeling in 5,409 adult women found two latent genetic factors across the obsessive-compulsive spectrum: one loading on all five phenotypes (most on body dysmorphic and hoarding symptoms) and a second loading only on trichotillomania and skin picking, with disorder-specific genetic effects for body dysmorphic and hoarding symptoms and negligible shared environmental influence [19]. The sample is adult and female; it supports grouping these disorders in one chapter without supporting any figure for children.

What this case cannot establish

Nadia's hair-pulling places her in a disorder whose prevalence is reported anywhere from 0.5% to 3.5% depending on the source, population and threshold; the mirror behavior places a 2% disorder with high impairment in the differential. The numbers justify asking; they do not answer.

Source status

#19, #20, #28, #31 from published abstracts; #21, #23, #24, #26 from open-access full text; #27 and #30 from the publisher's abstract pages; #29 from the live StatPearls chapter. #22 and #25 recovered in the citation check of 2026-10-05 (#22 relevant text; #25 abstract).

Figures for this chapter

Presentation

Two kinds of pulling

Nadia describes pulling in two ways, and the difference is not one of degree. The first she discovers by its product: hair on the keyboard, a hand already at the crown, no memory of starting. It occurs during sedentary, low-demand activity when her attention is elsewhere. The second is deliberate in its sequence even though she does not endorse its goal. She searches for a hair with a particular texture, feels a tightness before she finds it, pulls, and experiences brief relief followed by examination of the root. The trichotillomania literature names these patterns automatic and focused pulling, and most people who pull have some of each [22, 28, 30]. Recording which pattern dominates, and when, matters because the two are maintained and treated differently.

The tightness that precedes focused pulling deserves Nadia's own words rather than the word "tension." She locates it in her hands and behind her eyes, and it has a target: a hair that "feels wrong." Tension and relief were once diagnostic criteria for trichotillomania and are no longer required, partly because many people, especially children, pull without reporting them [22, 28]. Their presence in Nadia is an observation about her, not a requirement she has met.

Twirling a strand without pulling, which she does when the conversation turns to school, looks like the start of the same act. It has no product and no urge, and she does not lose track of it. Whether it sometimes proceeds to pulling is a question for a diary.

What the scalp establishes

The dermatologist's note supplies evidence of a kind psychiatric interviews rarely get. Hairs broken at different lengths within an irregular patch, no scaling, no exclamation-point hairs, and a negative pull test point toward mechanical removal rather than alopecia areata or tinea capitis; trichoscopic features described in children who pull include broken hairs of varying length and coiled hairs [31]. The examination does not say who pulled or why. It says the loss is consistent with pulling, which is what the psychiatric assessment has to explain.

Trichotillomania requires recurrent pulling that results in hair loss, repeated attempts to reduce or stop, distress or impairment, and the exclusion of a medical cause or a better psychiatric explanation [22, 28, 29]. Nadia satisfies each element. Eyelash pulling is a second and recent site, so the behavior is extending. She has never swallowed hair; trichophagia can produce a gastric trichobezoar, and the question must be asked because it is rarely volunteered [28, 29, 31].

Two kinds of mirror

Nadia's mornings contain two behaviors that share a location and look identical to her mother. In the first, she covers a patch that exists, checks whether the covering works, and stops when it does. The time is short, the goal is concrete, and the concern is proportionate to a visible consequence of pulling. This is concealment, and it belongs to the impairment produced by trichotillomania, with the swim team and the excused physical education class.

In the second, she inspects a feature that the dermatologist, the interviewer, and her mother do not see as abnormal, holds that it is obvious to everyone, discounts contrary evidence as politeness, photographs it under different lighting, and has asked about a procedure. This is the pattern of body dysmorphic disorder: preoccupation with a perceived defect not observable or slight to others, repetitive checking or comparing, and distress or impairment [23, 24]. In a series of 172 children and adolescents with the disorder, skin, hair, and nose were among the most common concerns, depression and anxiety were frequent, school functioning was often affected, and suicidal thoughts were common [24]. Onset is typically in adolescence, and earlier onset has been associated with more comorbidity and a higher rate of suicide attempts [25].

The two need separate descriptions because they have different endpoints. The first resolves when the hair regrows. The second does not, because the perceived flaw is not a consequence of anything she can stop doing.

Insight is the third thing the mirror shows. "My own hand, obviously" represents the pulling as her behavior. "A fact" is a belief held with enough conviction that reassurance is reinterpreted rather than absorbed. Recording the degree of conviction, and whether it shifts with mood or setting, is more useful than deciding at a first visit whether it is delusional; poor insight is common in adolescents with body dysmorphic disorder and does not by itself indicate psychosis [23, 24].

Convention matters here. Hair removal done to improve a perceived appearance defect is attributed to body dysmorphic disorder rather than trichotillomania [22, 28]. Nadia removes scalp hairs because they feel wrong, not because they look wrong, and hides the result. On the current account the two problems co-occur rather than one explaining the other.

The obsessive-compulsive question

Focused pulling has the surface of a compulsion: an aversive internal state, a repetitive act, relief. An uncle treated for obsessive-compulsive disorder adds family history, and twin research supports shared genetic liability across spectrum dimensions [19]. Neither establishes the disorder in Nadia. Compulsions in obsessive-compulsive disorder typically follow obsessions, intrusive thoughts with a feared consequence, and are performed to neutralize the threat. Nadia's pulling follows a sensory cue with no feared outcome, and the pens she lines up on her desk are a preference she shrugs about when they are moved. The interview still asks directly about intrusive thoughts, mental rituals, checking, and avoidance, because sensory-driven "not just right" compulsions occur within obsessive-compulsive disorder and cannot be told from focused pulling by the act alone [22, 28]. The question is answered by content, not by resemblance.

Keeping things: hoarding as a related pattern

The grandmother's unusable rooms and the mother's "a bit of that too" describe accumulation in two generations. Nadia keeps hair ties, samples, and packaging "for something" and protests when they are cleared. Hoarding disorder requires persistent difficulty discarding, a perceived need to save, distress at discarding, and clutter that compromises living areas; the last criterion is often unmet in young people because parents control the space and remove what accumulates [26]. Hoarding behaviors in children and adolescents commonly occur alongside other psychopathology rather than alone [27]. What can be recorded now is modest: Nadia assigns future use to objects most people would discard, and her protest is brief. Whether discarding would become impairing in a space she controlled is not something this history can show. It is a pattern to note, not a diagnosis.

Mood, function, and safety

Nadia's mood has been lower for two months, she has left a team she liked, and she calls herself disgusting. These symptoms may be consequences of the pulling and the preoccupation, an independent depressive episode, or both. The order of onset is consistent with the first, but sequence is not cause. She denied self-harm after a direct question. Given the suicidal ideation reported in adolescents with body dysmorphic disorder [24, 25], the question is repeated at each visit.

Perception, interpretation, and action side by side

Observation	What Nadia perceives	How she interprets it	What she does
Automatic pulling	Nothing until hair is in view	"I didn't decide"	Continues the task; shame later
Focused pulling	A hair with the wrong texture; tightness	"It has to come out"	Searches, pulls, examines the root
Patch concealment	A visible patch	"So nobody asks"	Arranges hair, stops when covered
Pore scrutiny	Pores at close range	"Everyone can see them"	Inspects, photographs, seeks a procedure
Keeping items	Objects with possible use	"For something"	Protests clearing, then moves on

What this case cannot establish

The history establishes hair pulling that produces loss, a second behavior that fits body dysmorphic disorder, a family with several spectrum phenotypes, and recent low mood. It cannot establish whether these are three disorders, one liability expressed several ways, or a primary problem with secondary consequences, nor what the family history means for Nadia. It cannot determine from one visit how fixed the conviction about her nose is, whether the low mood would persist if pulling stopped, or whether keeping objects would become hoarding in a room her mother did not clear. A pulling diary, a repeated safety question, and structured questions about obsessions would narrow these uncertainties.

Figures for this chapter

Functional neuroscience

Part 1. The functional layer

Two routes to the same hand movement

An action can be selected in more than one way. Goal-directed control is a process that selects an action according to the represented value of its outcome; if the outcome loses value, the action stops. Habitual control is a process that selects an action according to an association between a cue and a response, strengthened by repetition and relatively insensitive to what the action currently produces. Both run in a healthy brain, and which one governs a given act depends on practice, attention, and state.

Nadia's two pulling patterns map onto this distinction with unusual clarity. Automatic pulling has the profile of a habit. The cue is a posture and a context (hand near the head, sedentary task, attention absorbed elsewhere), the response runs without a represented goal, and she learns of it from its product. Focused pulling has the structure of a goal-directed act even though the goal is not one she endorses: she searches for a specific tactile target, acts on it, and evaluates the result. The distinction is functional, not moral. It predicts that reducing cue exposure will change the first pattern more than the second, and that the second will change when the relationship between the urge and the act changes.

This mapping is an interpretation of behavior, not a measurement of two control systems in Nadia. Laboratory tasks that separate habitual from goal-directed responding have been applied to obsessive-compulsive disorder and have reported a bias toward habitual responding under some conditions [185]. In trichotillomania, a systematic review of neuropsychological and neuroimaging studies found a small, methodologically heterogeneous literature with inconsistent findings [20]. The vocabulary is useful for describing Nadia; it does not carry a demonstrated group deficit with it.

One observation needs the capacity-versus-access distinction the casebook uses throughout. Nadia stops pulling when her mother enters the room. That shows access to inhibition under a strong external cue. It does not show that the same inhibition is available when she is alone, absorbed, and holding a hair that feels wrong.

The urge: a state, and a representation of what would end it

The tightness Nadia feels in her hands and behind her eyes is a premonitory urge state: a bodily condition that changes access to inhibition and biases action toward whatever has ended it before. A state is not a decision. It can be present with little content, as it seems to be when her hand drifts to her head during homework, or it can carry a precise urge representation, the content "this hair is wrong and should come out." Focused pulling has both; automatic pulling has mostly the first.

Perceiving that one hair is coarser than its neighbors is not abnormal. Most people can feel it. What differs is what follows the perception: in Nadia the difference is registered as something to be corrected. Error signaling is the process by which a mismatch between an expected and an actual state is flagged and given priority. Exaggerated error signals have been studied in obsessive-compulsive disorder using electrophysiological markers of performance monitoring [186]. Whether the same process is at work in trichotillomania is not established. What the vocabulary does for Nadia is separate the sensation (a hair feels different), the signal (this is wrong), and the act (pull), so that treatment can aim at the middle term.

The urge in trichotillomania also differs in content from an obsession. An obsession is propositional: a thought about contamination, harm, or blame with a feared consequence. Nadia's urge is sensory and has no feared consequence. That is why the obsessive-compulsive differential turns on content rather than on the resemblance between pulling and a compulsion.

Negative reinforcement: how relief teaches

Negative reinforcement is a learning process in which an action that removes an aversive state becomes more likely in that state. Nadia's relief "for a second" is the reinforcing event. Its brevity does not weaken the learning; short, reliable relief is an effective teacher, and the return of the aversive state supplies the next occasion. Examining and biting the root may add a second, positive reinforcer, a sensory consequence that is itself sought. Automatic pulling is likely reinforced differently, by the relief of boredom or by low-level tactile stimulation during an under-stimulating task. The functional analysis of pulling in terms of its antecedents and consequences is the basis of the assessment instruments and the behavioral treatments described in the trichotillomania reviews [22, 28, 30].

The learning account explains why willpower is a poor predictor. Each pull is followed by relief and each act of restraint is followed by the persistence of the urge. The contingencies favor pulling until something changes either the urge state or what happens after it.

Motor inhibition

Motor inhibition capacity is the ability, under good conditions, to cancel a prepared or ongoing movement. Studies of adults with trichotillomania have reported slower stopping on stop-signal tasks, which the reviews interpret as a difficulty with motor inhibition [20, 28]. The finding is a group difference on a laboratory task, obtained mostly in adults, in a literature the systematic review describes as small and inconsistent [20]. It says nothing about Nadia's stop-signal performance and would not, even if she were tested, establish that a stopping deficit causes her pulling. The clinical relevance is narrower: if a competing response is to be trained, it is easier to insert a new action before the pull than to cancel the pull once begun.

Body-image representation and perceptual over-focus

A body-image representation is a model of one's own appearance built from perception, memory, comparison, and the reactions of others. Everyone has one; it is usually updated by evidence. Nadia's representation of her nose has two properties that matter. It is held with high conviction, and it resists updating: the dermatologist's judgment and the interviewer's are reinterpreted as politeness rather than absorbed.

Local-detail bias is an attentional and perceptual process in which processing favors local features over global configuration. Small laboratory studies of adults with body dysmorphic disorder have reported abnormal local and global processing of faces and houses [187, 188]. Those are task findings in adult samples, and they do not show how Nadia, at fourteen, processes her own face. Nadia's behavior supplies the local detail without any need to assume an altered retina. At close range and under strong light, pores are large. Photographing under varied lighting samples the feature under conditions that maximize it. Each sample enters the representation as evidence, and the representation is updated from what she inspects rather than from what others see at conversational distance. This is a description of the inputs, not a demonstration of an abnormal perceptual system.

Insight belongs at this level. The difference between "my own hand, obviously" and "a fact" is the difference between a representation tagged as a belief about oneself and one tagged as a property of the world. The tag can vary with mood and setting. It is a variable to track, not a fixed trait.

Assigning value to objects

Keeping objects "for something" involves object-value assignment, a process that attaches expected use or emotional significance to an item and makes discarding it a loss. In adolescents the environment is largely controlled by parents, so the behavior is often visible only as protest [26]. Nadia's protest is brief. Nothing in this history shows that discarding is aversive enough to organize her behavior, which is what distinguishes hoarding from keeping.

Part 2. Circuits, development, and genes

Circuits that select and stop actions

Action selection and its inhibition depend on loops connecting frontal cortex, striatum, and thalamus. Alterations in these loops are widely reported in obsessive-compulsive disorder [189]. In trichotillomania, the systematic review found structural reports involving striatal, cerebellar, and white-matter regions that were not consistently replicated across small samples [20]. A multi-site analysis of cortical thickness in trichotillomania, in an adult sample, reported reduced thickness in frontal regions including the right inferior frontal gyrus, an area implicated in stopping movements [21]. That finding connects a structural group difference to the inhibitory-control account above. It is cross-sectional, so it cannot separate cause from consequence, and it describes a distribution across participants rather than any one of them.

Group imaging studies have examined visual and affective networks in body dysmorphic disorder in relation to detail-focused processing [187, 188]. No imaging study is needed for Nadia, and none would change the formulation.

Development

Trichotillomania most often begins around the transition into adolescence, and pulling that begins in early childhood tends to run a different, often self-limiting course [28, 29, 30, 31]. Nadia's onset at thirteen, after a disliked haircut and during examinations, fits the typical age. The haircut and the examinations are context, not cause; a change in the feel of the hair and a period of sedentary study supplied cues and occasions for a behavior that then acquired its own maintenance.

Body dysmorphic disorder also typically begins in adolescence, and onset before adulthood has been associated with more comorbidity and a higher rate of suicide attempts in adult samples assessed retrospectively [25]. The adolescent series adds that impairment at school and suicidal thoughts are common at this age [24]. Hoarding symptoms can begin in childhood and adolescence, but full disorder is rarely diagnosed in young people, in part because parents limit accumulation [26].

Genes

A twin study of dimensional obsessive-compulsive spectrum phenotypes, covering obsessive-compulsive symptoms, body dysmorphic concerns, hoarding, hair pulling, and skin picking, found a common genetic factor influencing all of them together with genetic factors specific to individual dimensions, and environmental influences that were mostly not shared within families [19]. That structure is what Nadia's family history looks like from the inside: an uncle with obsessive-compulsive disorder, a grandmother with accumulation, a mother who bites her nails, and a daughter who pulls and checks. Shared liability predicts that several phenotypes will appear in one family. It does not predict which one a given child will show, and it does not make any one of Nadia's behaviors a consequence of the others.

Moving between levels of evidence

A learning account describes how pulling could be maintained. A stop-signal study describes a group's performance on a task. A cortical-thickness study describes a distribution of anatomy. A twin study describes the sources of variation in a population. Each is evidence at its own level. None identifies the mechanism in Nadia, and the formulation that guides her treatment is built from her observed antecedents and consequences, with these findings as background.

What this case cannot establish

The functional account separates automatic from focused pulling, describes the urge as a state with content, and identifies negative reinforcement as a plausible maintaining process. It cannot establish that Nadia has a measurable deficit in motor inhibition, a bias toward habitual control, or an exaggerated error signal; those are constructs drawn from group studies she has not been part of. It cannot establish that her nose preoccupation reflects a perceptual abnormality rather than a representation updated from close-range sampling. It cannot say what her family history contributes to her own biology. It can say what to change and what to measure.

Figures for this chapter

Treatment

What the plan targets

Nadia's care has five targets that the presentation and the functional account keep apart: focused pulling, which runs on an urge-pull-relief loop; automatic pulling, which runs on cues; the preoccupation with her nose, which runs on a representation that resists updating; her mood and her withdrawal from swimming; and her safety, which is asked about at every visit. The patch concealment is not a target. It is a proportionate response to a visible consequence, and it will resolve when the hair does.

Her own goals are stated plainly: hair back, swimming in June without a cap. Both are measurable, and the second gives the plan a date.

Behavior therapy for pulling

The best-supported treatment for trichotillomania is behavior therapy built around habit reversal training, with stimulus control added for automatic pulling [22, 28, 30]. Habit reversal has three parts. Awareness training teaches Nadia to notice the earliest links of the chain, the hand rising, the fingertips searching, the tightness. A competing response is an action incompatible with pulling, such as clenching the fists or gripping the chair, held for a minute when the urge or the early movement is noticed. Social support enlists her mother to prompt and praise the competing response without commenting on pulling itself. Stimulus control changes the cues: gloves or a bandana during homework and scrolling, a fidget object in the pulling hand, a different seat, shorter sedentary stretches, and a bathroom mirror that is not used with the door locked.

The pediatric evidence is small but direct. A randomized trial of behavior therapy against a minimal-attention control in children and adolescents found greater reduction in pulling severity with behavior therapy, with gains maintained at short-term follow-up [30]. Adult trials of habit reversal, including versions augmented with acceptance-based or dialectical skills for urge tolerance, support the same core components [22, 28]. The reviews also report that relapse after treatment is common, which argues for booster sessions and for treating the June deadline as a milestone rather than an endpoint [22, 28].

The two pulling patterns are treated differently within one program, and this is where the functional account earns its place. Stimulus control acts on automatic pulling by removing the cue and blocking the response. For focused pulling, the target is the link between the urge state and the act. Awareness plus a competing response inserts a new action at that link, and acceptance-based components teach Nadia to hold the tightness without acting on it long enough for it to pass. Neither component claims to remove the sensation of a coarse hair. Progress is measured with a pulling diary, a standardized severity scale, and scalp photographs taken under the same conditions each month [22, 30]. Regrowth is slow, so the diary and the scale will move before the photographs do.

Medication for pulling

Pharmacotherapy for trichotillomania is a clear example of mechanism and outcome failing to line up. Selective serotonin reuptake inhibitors, the first-line medications for obsessive-compulsive disorder, have not shown consistent benefit over placebo for hair pulling in controlled trials [22, 28]. A small early trial found clomipramine superior to desipramine, but its size limits the conclusion [28]. Olanzapine reduced pulling in one small adult trial, at the cost of the metabolic and sedative effects that make it a poor choice for a fourteen-year-old with mild symptoms [22, 28].

N-acetylcysteine is the most instructive case. Its rationale is modulation of glutamate signaling in circuits involved in compulsive behavior. A randomized trial in adults found it superior to placebo for hair pulling; a subsequent randomized trial in children and adolescents did not [22, 28]. The rationale was the same in both trials, and the outcomes diverged. A mechanism that is plausible at the level of a transmitter does not predict the outcome in a particular age group, and the pediatric result is the one that applies to Nadia. The pediatric review published before that trial could only note adult data [30]; the later reviews carry the negative pediatric finding [22, 28].

For Nadia, no medication is started for pulling. If a medication is later considered for depressive symptoms or for body dysmorphic disorder, its effect on pulling is observed rather than assumed.

The nose: a separate problem with its own evidence

Body dysmorphic disorder is not treated by treating the pulling, and the temptation to fold it into "an OCD spectrum thing" and hope should be resisted. Cognitive behavioral therapy developed for body dysmorphic disorder and adapted for young people has been tested in a randomized trial in adolescents, with benefit over a control condition [23]. Its components differ from habit reversal. They include psychoeducation that does not argue about the pores, exposure to situations she avoids (being seen close up, being photographed by someone else, swimming), response prevention for checking and photographing, mirror retraining that practices looking at the whole face at conversational distance without inspection, and work with the family to reduce reassurance. Reassurance is the family's natural response and it does not work, because each "you look fine" is a data point she has already learned to discount.

Medication evidence for body dysmorphic disorder is stronger in adults than in adolescents; serotonin reuptake inhibitors have controlled-trial support in adults, and adolescent evidence is largely uncontrolled [23]. Cosmetic and dermatologic procedures do not relieve the preoccupation and are sought by a proportion of young people with the disorder [23, 24]. The laser question is answered with that fact, and the dermatologist is asked to hold the same line.

Safety monitoring is part of this arm of treatment rather than an add-on. Suicidal thoughts were common in the adolescent series and suicide attempts were more frequent with early onset in adult samples [24, 25]. Nadia's denial is recorded and the question is repeated.

Insight is handled as a variable. Nadia is not asked to agree that her nose is normal before treatment begins; she is asked whether the time at the mirror and the deleted photographs are costing her things she wants, which she has already said they are. If the conviction does not shift at all with mood or setting over several weeks, that is noted, and the mood assessment is revisited.

The open differentials

If structured questioning establishes obsessions with feared consequences and neutralizing compulsions, obsessive-compulsive disorder is treated on its own evidence base, cognitive behavioral therapy with exposure and response prevention and, where indicated, a serotonin reuptake inhibitor [190]. The pulling would still be treated with habit reversal, because the medication evidence for the two conditions differs.

The keeping of objects is not treated. It is monitored, and Nadia's mother is asked to involve her in decisions about what leaves the room rather than clearing it while she is at school. That is not a treatment for hoarding disorder, which she does not have; it preserves the opportunity for Nadia to practice discarding rather than only to lose things. A 2016 review described the evidence on treating hoarding in children and adolescents as sparse [191].

Mood and participation

Her lower mood is followed alongside the pulling and the preoccupation rather than treated separately at the outset. If it lifts as the behaviors change, the sequence supports the account that it was secondary. If it persists or deepens, it is assessed and treated as a depressive episode according to the evidence set out in the Depressive Disorders module (Jonah), and the safety question rises in priority. Swimming is scheduled as a graded exposure that serves both arms of treatment: a cap in June, then a practice without one when the photographs show regrowth.

Sequence and review

Assessment of safety and mood comes first and is repeated. Behavior therapy for pulling begins in the first weeks, since it is the intervention with the most direct evidence and the least risk. Cognitive behavioral therapy for body dysmorphic disorder runs alongside it once the criteria are confirmed, with the same clinician where possible. Medication is considered only for the appearance preoccupation or for depression, on their own evidence, and not for pulling. Review at eight weeks asks four questions: has focused pulling changed, has automatic pulling changed, has mirror time changed, and is she planning to swim.

What this case cannot establish

The plan rests on trial evidence for outcomes: pulling severity after behavior therapy, appearance-related symptoms after cognitive behavioral therapy for body dysmorphic disorder, and the absence of a pediatric benefit from N-acetylcysteine. It cannot establish which component of behavior therapy will help Nadia, whether reduced pulling will lift her mood, or whether her conviction about her nose will change with treatment. It cannot establish that the medications that failed in trials would fail in her, only that there is no evidence they would help. The functional account tells the clinician where to intervene; the trials tell the clinician how much to expect; Nadia's diary and photographs tell everyone what actually happened.

Figures for this chapter

---