Trichotillomania | |
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Other names | Trichotillosis, hair-pulling disorder, hairs-pulling disorder, [1] compulsive hair pulling |
A pattern of incomplete hair loss on the scalp of a person with trichotillomania | |
Pronunciation | |
Specialty | Dermatology, psychiatry |
Symptoms | Visible hair loss, distress [1] [2] |
Usual onset | Childhood or adolescence [2] |
Risk factors | Family history, anxiety, obsessive compulsive disorder [1] |
Diagnostic method | Based on symptoms, seeing broken hairs [1] |
Differential diagnosis | Body dysmorphic disorder [1] |
Treatment | Cognitive behavioral therapy, clomipramine [3] |
Frequency | ~2% [2] [3] |
Trichotillomania (TTM), also known as hair-pulling disorder or compulsive hair pulling, is a mental disorder characterized by a long-term urge that results in the pulling out of one's own hair. [2] [4] A brief positive feeling may occur as hair is removed. [5] Efforts to stop pulling hair typically fail. Hair removal may occur anywhere; however, the head and around the eyes are most common. The hair pulling is to such a degree that it results in distress and hair loss can be seen. [1] [2]
As of 2023, the specific cause or causes of trichotillomania are unclear. Trichotillomania is probably due to a combination of genetic and environmental factors. [6] The disorder may run in families. [7] It occurs more commonly in those with obsessive compulsive disorder (OCD). Episodes of pulling may be triggered by anxiety. People usually acknowledge that they pull their hair, and broken hairs may be seen on examination. Other conditions that may present similarly include body dysmorphic disorder; however, in that condition people remove hair to try to improve what they see as a problem in how they look. [1]
Treatment is typically with cognitive behavioral therapy. [3] The medication clomipramine may also be helpful, as will keeping fingernails clipped. [3] Trichotillomania is estimated to affect one to four percent of people. [2] [3] Trichotillomania most commonly begins in childhood or adolescence. [2] Women are affected about 10 times more often than men. [1] The name was created by François Henri Hallopeau in 1889, from the Greek θρίξ, thrix (meaning 'hair'), along with τίλλειν, tíllein (meaning 'to pull'), and μανία, mania (meaning 'madness'). [8]
Trichotillomania is usually confined to one or two sites, [9] but can involve multiple sites. The scalp is the most common pulling site, followed by the eyebrows, eyelashes, face, arms, and legs. [10] Some less common areas include the pubic area, underarms, beard, and chest. [11] The classic presentation is the "Friar Tuck" form of crown alopecia (loss of hair at the "crown" of the head, also known as the "vertex"). [12] Children are less likely to pull from areas other than the scalp. [10]
People with trichotillomania often pull only one hair at a time and these hair-pulling episodes can last for hours at a time. Some individuals may experience more satisfaction after pulling an anagen phase hair with the gel-like inner root sheath still surrounding the base of the hair. Trichotillomania can go into remission-like states where the individual may not experience the urge to "pull" for days, weeks, months, or even years. [13]
Individuals with trichotillomania exhibit hair of differing lengths; some are broken hairs with blunt ends, some new growth with tapered ends, some broken mid-shaft, or some uneven stubble. Scaling on the scalp is not present, overall hair density is normal, and a hair pull test is negative (the hair does not pull out easily). Hair is often pulled out leaving an unusual shape. Individuals with trichotillomania may be secretive of the hair pulling behavior, which is often associated with feelings of shame associated with it. [10]
An additional psychological effect can be low self-esteem, often associated with being shunned by peers and the fear of socializing, due to appearance and negative attention they may receive. [14] Some people with trichotillomania wear hats, wigs, false eyelashes, use makeup such as an eyebrow pencil, or style their hair in an effort to avoid such attention. [3] There seems to be a strong stress-related component. In low-stress environments, some exhibit no symptoms (known as "pulling") whatsoever, and this "pulling" often resumes upon leaving this environment. [15] Some individuals with trichotillomania may feel isolated, as if they are the only person with this problem, due to low rates of reporting. [16]
For some people, trichotillomania is a mild, if frustrating, problem. But for many, embarrassment about hair pulling causes isolation and results in a great deal of emotional distress, placing them at risk for a co-occurring psychiatric disorder, such as a mood or anxiety disorder. Hair pulling can lead to tension and strained relationships with family members and friends. Family members may need professional help in coping with this problem. [17]
Other medical complications include infection, permanent loss of hair, repetitive stress injury, carpal tunnel syndrome, and gastrointestinal obstruction as a result of trichophagia. [9] In trichophagia, people with trichotillomania also ingest the hair that they pull; in extreme (and rare) cases this can lead to a hair ball (trichobezoar). [10] Rapunzel syndrome is an extreme form of trichobezoar in which the "tail" of the hair ball extends into the intestines and can be fatal if misdiagnosed. [10] [18] [19] [20]
Environment is a large factor which affects hair pulling. [21] Sedentary activities such as being in a relaxed environment are conducive to hair pulling. [21] [22] A common example of a sedentary activity promoting hair pulling is lying in a bed while trying to rest or fall asleep. [21] An extreme example of automatic trichotillomania is "sleep-isolated" trichotillomania, where patients pull their hair out while asleep. [21] [23]
Anxiety, depression and obsessive–compulsive disorder are more frequently encountered in people with trichotillomania. [9] [24] Trichotillomania has a high overlap with post traumatic stress disorder,[ citation needed ] and some cases of trichotillomania may be triggered by stress. Another school of thought emphasizes hair pulling as addictive or negatively reinforcing, as it is associated with rising tension beforehand and relief afterward. [9] A neurocognitive model — the notion that the basal ganglia play a role in habit formation and that the frontal lobes are critical for normally suppressing or inhibiting such habits — sees trichotillomania as a habit disorder. [9]
In several MRI studies, it has been found that people with trichotillomania have more gray matter on average than those who do not have the disorder. [25] One study found that individuals with trichotillomania have decreased cerebellar volume on average, [9] [26] which suggests some differences between OCD and trichotillomania. [9] An fMRI study reported decreased activation in the basal ganglia, dorsolateral prefrontal cortex, and dorsal anterior cingulate cortex in people with trichotillomania. [27] Abnormalities in the caudate nucleus are noted in OCD, but there is no evidence to support that these abnormalities can also be linked to trichotillomania. [9]
It is likely that a combination of multiple genes confers vulnerability to trichotillomania. [9] Mutations in the SLITRK1, [9] [28] 5HT2A, [29] SAPAP3, [30] and FOXP1 [31] genes have been associated with trichotillomania. In addition, HOXB8 knockout mice display pathological grooming behavior similar to trichotillomania, [32] [33] although associations between trichotillomania and the HOXB8 gene have not been demonstrated in humans. [34]
Patients may be ashamed or actively attempt to disguise their symptoms. This can make diagnosis difficult as symptoms are not always immediately obvious, or have been deliberately hidden to avoid disclosure. [9] If the patient admits to hair pulling, diagnosis is not difficult; if patients deny hair pulling, a differential diagnosis must be pursued. [10] The differential diagnosis will include evaluation for alopecia areata, iron deficiency, hypothyroidism, tinea capitis, traction alopecia, alopecia mucinosa, thallium poisoning, and loose anagen syndrome. [3] [10] In trichotillomania, a hair pull test is negative. [10]
A biopsy can be performed and may be helpful; it reveals traumatized hair follicles with perifollicular hemorrhage, fragmented hair in the dermis, empty follicles, and deformed hair shafts. Multiple catagen hairs are typically seen. An alternative technique to biopsy, particularly for children, is to shave a part of the involved area and observe for regrowth of normal hairs. [35]
Diagnostic criteria from the DSM-5 provides the following criteria for trichotillomania: [36]
Trichotillomania is defined as a self-induced and recurrent loss of hair. [10] It includes the criterion of an increasing sense of tension before pulling the hair and gratification or relief when pulling the hair. [9] However, some people with trichotillomania do not endorse the inclusion of "rising tension and subsequent pleasure, gratification, or relief" as part of the criteria [9] because many individuals with trichotillomania may not realize they are pulling their hair, and patients presenting for diagnosis may deny the criteria for tension prior to hair pulling or a sense of gratification after hair is pulled. [10]
Trichotillomania may lie on the obsessive-compulsive spectrum, [3] also encompassing obsessive-compulsive disorder (OCD), body dysmorphic disorder (BDD), nail biting (onychophagia) and skin picking (dermatillomania), tic disorders and eating disorders. These conditions may share clinical features, genetic contributions, and possibly treatment response; however, differences between trichotillomania and OCD are present in symptoms, neural function and cognitive profile. [9] In the sense that it is associated with irresistible urges to perform unwanted repetitive behavior, trichotillomania is akin to some of these conditions, and rates of trichotillomania among relatives of OCD patients is higher than expected by chance. [9] However, differences between the disorder and OCD have been noted, including: differing peak ages at onset, rates of comorbidity, gender differences, and neural dysfunction and cognitive profile. [9] When it occurs in early childhood, it can be regarded as a distinct clinical entity. [9]
Because trichotillomania can be present in multiple age groups, it is helpful in terms of prognosis and treatment to approach three distinct subgroups by age: preschool age children, preadolescents to young adults, and adults. [10]
In preschool age children, trichotillomania is considered benign. For these children, hair-pulling is considered either a means of exploration or something done subconsciously, similar to nail-biting and thumb-sucking, and almost never continues into further ages. [37]
The most common age of onset of trichotillomania is between ages 9 and 13. In this age range, trichotillomania is usually chronic, and continues into adulthood. Trichotillomania that begins in adulthood most commonly arises from underlying psychiatric causes. [37]
Trichotillomania is often not a focused act, but rather hair pulling occurs in a "trance-like" state; [21] hence, trichotillomania is subdivided into "automatic" versus "focused" hair pulling. [10] Children are more often in the automatic, or unconscious, subtype and may not consciously remember pulling their hair. Other individuals may have focused, or conscious, rituals associated with hair pulling, including seeking specific types of hairs to pull, pulling until the hair feels "just right", or pulling in response to a specific sensation. [10] Knowledge of the subtype is helpful in determining treatment strategies. [10]
Treatment is based on a person's age. Most pre-school age children outgrow the condition if it is managed conservatively. In young adults, establishing the diagnosis and raising awareness of the condition is an important reassurance for the family and patient. Non-pharmacological interventions, including behavior modification programs, may be considered; referrals to psychologists or psychiatrists may be considered when other interventions fail. When trichotillomania begins in adulthood, it is often associated with other mental disorders, and referral to a psychologist or psychiatrist for evaluation or treatment is considered best. The hair pulling may resolve when other conditions are treated. [10]
Habit reversal training (HRT) has the highest rate of success in treating trichotillomania. [10] HRT has also been shown to be a successful adjunct to medication as a way to treat trichotillomania. [9] [38] With HRT, the individual is trained to learn to recognize their impulse to pull and also teach them to redirect this impulse. In comparisons of behavioral versus pharmacologic treatment, cognitive behavioral therapy (including HRT) have shown significant improvement over medication alone. [9] [10] It has also proven effective in treating children. [10] Biofeedback, cognitive-behavioral methods, and hypnosis may improve symptoms. [39] Acceptance and commitment therapy (ACT) is also demonstrating promise in trichotillomania treatment. [40] A systematic review from 2012 found tentative evidence for "movement decoupling". [41]
The United States Food and Drug Administration (FDA) has not approved any medications for trichotillomania treatment. [42]
However, some medications have been used to treat trichotillomania, with mixed results. Treatment with clomipramine, a tricyclic antidepressant, was shown in a small double-blind study to improve symptoms, [43] but results of other studies on clomipramine for treating trichotillomania have been inconsistent. [10] Naltrexone may be a viable treatment. [44] Fluoxetine and other selective serotonin reuptake inhibitors (SSRIs) have limited usefulness in treating trichotillomania, and can often have significant side effects. [45] Behavioral therapy has proven more effective when compared to fluoxetine. [10] There is little research on the effectiveness of behavioral therapy combined with medication and robust evidence from high-quality studies is lacking. [36] Acetylcysteine treatment stemmed from an understanding of glutamate's role in regulation of impulse control. [46]
A study published in March 2023 studied the application of memantine, a drug typically used to treat symptoms of Alzheimer's disease, to treat patients with trichotillomania. Similar to NAC mentioned above, memantine acts to regulate glutamate levels. [47]
Different medications, depending on the individual, may increase hair pulling. [42]
Technology can be used to augment habit reversal training or behavioral therapy. Several mobile apps exist to help log behavior and focus on treatment strategies. [48] There are also wearable devices that track the position of a user's hands. They produce sound or vibrating notifications so that users can track rates of these events over time. [49]
When it occurs in early childhood (before five years of age), the condition is typically self-limiting and intervention is not required. [9] In adults, the onset of trichotillomania may be secondary to underlying psychiatric disturbances, and symptoms are generally more long-term. [10]
Secondary infections may occur due to picking and scratching, but other complications are rare. [10] Individuals with trichotillomania often find that support groups are helpful in living with and overcoming the disorder. [10]
Although no broad-based population epidemiologic studies had been conducted as of 2009, the lifetime prevalence of trichotillomania is estimated to be between 0.6% and 4.0% of the overall population. [3] With a 1% prevalence rate, 2.5 million people in the U.S. may have trichotillomania at some time during their lifetimes. [50]
Trichotillomania is diagnosed in all age groups; onset is more common during preadolescence and young adulthood, with mean age of onset between 9 and 13 years of age, [10] and a notable peak at 12–13. [9] Among preschool children the genders are equally represented; there appears to be a female predominance among preadolescents to young adults, with between 70% and 93% of patients being female. [10] Among adults, females typically outnumber males by 3 to 1. [9]
"Automatic" pulling occurs in approximately three-quarters of adult patients with trichotillomania. [10]
Hair pulling was first mentioned by Aristotle in the fourth century B.C., [51] was first described in modern literature in 1885, [52] and the term trichotillomania was coined by the French dermatologist François Henri Hallopeau in 1889. [3] [9]
In 1987, trichotillomania was recognized in the Diagnostic and Statistical Manual of the American Psychiatric Association, third edition-revised (DSM-III-R). [53]
Support groups and internet sites can provide recommended educational material and help persons with trichotillomania in maintaining a positive attitude and overcoming the fear of being alone with the disorder. [9] [10]
A documentary film exploring trichotillomania, Bad Hair Life, was the 2003 winner of the International Health & Medical Media Award for best film in psychiatry and the winner of the 2004 Superfest Film Festival Merit Award. [54] [55] [56]
Trichster is a 2016 documentary that follows seven individuals living with trichotillomania, as they navigate the complicated emotions surrounding the disorder, and the effect it has on their daily lives. [57]
The trichotillomania of a prominent character is a key plot element in the 1999 novel Whatever Love Means by David Baddiel.[ citation needed ]
Ashley Barret, a character portrayed by Colby Minifie in the superhero fiction series The Boys, is shown suffering from it.
On the 2017 album, 20s a Difficult Age by Marcus Orelias, there is a song called "Trichotillomania". [58]
Anxiety disorders are a group of mental disorders characterized by significant and uncontrollable feelings of anxiety and fear such that a person's social, occupational, and personal functions are significantly impaired. Anxiety may cause physical and cognitive symptoms, such as restlessness, irritability, easy fatigue, difficulty concentrating, increased heart rate, chest pain, abdominal pain, and a variety of other symptoms that may vary based on the individual.
Trichophagia is a form of disordered eating in which persons with the disorder suck on, chew, swallow, or otherwise eat hair. The term is derived from ancient Greek θρίξ, thrix ("hair") and φαγεῖν, phagein. Tricho-phagy refers only to the chewing of hair, whereas tricho-phagia is ingestion of hair, but many texts refer to both habits as just trichophagia. It is considered a chronic psychiatric disorder of impulse control. Trichophagia belongs to a subset of pica disorders and is often associated with trichotillomania, the compulsive pulling out of ones own hair. People with trichotillomania often also have trichophagia, with estimates ranging from 48-58% having an oral habit such as biting or chewing, and 4-20% actually swallowing and ingesting their hair. Extreme cases have been reported in which patients consume hair found in the surrounding environment, including the hair of other people and animals. In an even smaller subset of people with trichotillomania, their trichophagia can become so severe that they develop a hair ball. Termed a trichobezoar, these masses can be benign, or cause significant health concerns and require emergency surgery to remove them. Rapunzel syndrome is a further complication whereby the hair ball extends past the stomach and can cause blockages of gastrointestinal system.
Hoarding disorder (HD) or Plyushkin's disorder, is a mental disorder characterised by persistent difficulty in parting with possessions and engaging in excessive acquisition of items that are not needed or for which no space is available. This results in severely cluttered living spaces, distress, and impairment in personal, family, social, educational, occupational, or other important areas of functioning. Excessive acquisition is characterized by repetitive urges or behaviours related to amassing or buying property. Difficulty discarding possessions is characterized by a perceived need to save items and distress associated with discarding them. Accumulation of possessions results in living spaces becoming cluttered to the point that their use or safety is compromised. It is recognised by the eleventh revision of the International Classification of Diseases (ICD-11) and the Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-5).
Rapunzel syndrome is an extremely rare intestinal condition in humans resulting from ingesting hair (trichophagia). The syndrome is named after the long-haired girl Rapunzel in the fairy tale by the Brothers Grimm. Trichophagia is sometimes associated with the hair-pulling disorder trichotillomania. This syndrome is a rare and unusual form of trichobezoar. Since 1968, there have been fewer than 40 documented cases in the literature. This syndrome occurs when the trichobezoar (hairball) reaches past the small intestine, and sometimes even into the colon producing a long tail-like extension of hair.
Clomipramine, sold under the brand name Anafranil among others, is a tricyclic antidepressant (TCA). It is used in the treatment of various conditions, most-notably obsessive–compulsive disorder but also many other disorders, including hyperacusis, panic disorder, major depressive disorder, trichotillomania, body dysmorphic disorder and chronic pain. It has also been notably used to treat premature ejaculation and the cataplexy associated with narcolepsy.
Impulse-control disorder (ICD) is a class of psychiatric disorders characterized by impulsivity – failure to resist a temptation, an urge, or an impulse; or having the inability to not speak on a thought. Many psychiatric disorders feature impulsivity, including substance-related disorders, behavioral addictions, attention deficit hyperactivity disorder, autism spectrum disorder, fetal alcohol spectrum disorders, antisocial personality disorder, borderline personality disorder, conduct disorder and some mood disorders.
Excoriation disorder, more commonly known as dermatillomania, is a mental disorder on the obsessive–compulsive spectrum that is characterized by the repeated urge or impulse to pick at one's own skin, to the extent that either psychological or physical damage is caused.
Pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections (PANDAS) is a controversial hypothetical diagnosis for a subset of children with rapid onset of obsessive-compulsive disorder (OCD) or tic disorders. Symptoms are proposed to be caused by group A streptococcal (GAS), and more specifically, group A beta-hemolytic streptococcal (GABHS) infections. OCD and tic disorders are hypothesized to arise in a subset of children as a result of a post-streptococcal autoimmune process. The proposed link between infection and these disorders is that an autoimmune reaction to infection produces antibodies that interfere with basal ganglia function, causing symptom exacerbations, and this autoimmune response results in a broad range of neuropsychiatric symptoms.
An intrusive thought is an unwelcome, involuntary thought, image, or unpleasant idea that may become an obsession, is upsetting or distressing, and can feel difficult to manage or eliminate. When such thoughts are associated with obsessive-compulsive disorder (OCD), Tourette's syndrome (TS), depression, body dysmorphic disorder (BDD), and sometimes attention-deficit hyperactivity disorder (ADHD), the thoughts may become paralyzing, anxiety-provoking, or persistent. Intrusive thoughts may also be associated with episodic memory, unwanted worries or memories from OCD, post-traumatic stress disorder, other anxiety disorders, eating disorders, or psychosis. Intrusive thoughts, urges, and images are of inappropriate things at inappropriate times, and generally have aggressive, sexual, or blasphemous themes.
Habit reversal training (HRT) is a "multicomponent behavioral treatment package originally developed to address a wide variety of repetitive behavior disorders".
The obsessive–compulsive spectrum is a model of medical classification where various psychiatric, neurological and/or medical conditions are described as existing on a spectrum of conditions related to obsessive–compulsive disorder (OCD). "The disorders are thought to lie on a spectrum from impulsive to compulsive where impulsivity is said to persist due to deficits in the ability to inhibit repetitive behavior with known negative consequences, while compulsivity persists as a consequence of deficits in recognizing completion of tasks." OCD is a mental disorder characterized by obsessions and/or compulsions. An obsession is defined as "a recurring thought, image, or urge that the individual cannot control". Compulsion can be described as a "ritualistic behavior that the person feels compelled to perform". The model suggests that many conditions overlap with OCD in symptomatic profile, demographics, family history, neurobiology, comorbidity, clinical course and response to various pharmacotherapies. Conditions described as being on the spectrum are sometimes referred to as obsessive–compulsive spectrum disorders.
Sexual obsessions are persistent and unrelenting thoughts about sexual activity. In the context of obsessive-compulsive disorder (OCD), these are extremely common, and can become extremely debilitating, making the person ashamed of the symptoms and reluctant to seek help. A preoccupation with sexual matters, however, does not only occur as a symptom of OCD, they may be enjoyable in other contexts.
Compulsive behavior is defined as performing an action persistently and repetitively. Compulsive behaviors could be an attempt to make obsessions go away. Compulsive behaviors are a need to reduce apprehension caused by internal feelings a person wants to abstain from or control. A major cause of compulsive behavior is said to be obsessive–compulsive disorder (OCD). "The main idea of compulsive behavior is that the likely excessive activity is not connected to the purpose to which it appears directed." There are many different types of compulsive behaviors including shopping, hoarding, eating, gambling, trichotillomania and picking skin, itching, checking, counting, washing, sex, and more. Also, there are cultural examples of compulsive behavior.
Exposure therapy is a technique in behavior therapy to treat anxiety disorders. Exposure therapy involves exposing the patient to the anxiety source or its context. Doing so is thought to help them overcome their anxiety or distress. Numerous studies have demonstrated its effectiveness in the treatment of disorders such as generalized anxiety disorder (GAD), social anxiety disorder (SAD), obsessive-compulsive disorder (OCD), post-traumatic stress disorder (PTSD), and specific phobias.
Obsessive–compulsive disorder (OCD) is a mental disorder in which an individual has intrusive thoughts and feels the need to perform certain routines (compulsions) repeatedly to relieve the distress caused by the obsession, to the extent where it impairs general function.
Body-focused repetitive behavior (BFRB) is an umbrella name for impulse control behaviors involving compulsively damaging one's physical appearance or causing physical injury.
The cause of obsessive–compulsive disorder is understood mainly through identifying biological risk factors that lead to obsessive–compulsive disorder (OCD) symptomology. The leading hypotheses propose the involvement of the orbitofrontal cortex, basal ganglia, and/or the limbic system, with discoveries being made in the fields of neuroanatomy, neurochemistry, neuroimmunology, neurogenetics, and neuroethology.
The delayed-maturation theory of obsessive–compulsive disorder suggests that obsessive–compulsive disorder (OCD) can be caused by delayed maturation of the frontal striatal circuitry or parts of the brain that make up the frontal cortex, striatum, or integrating circuits. Some researchers suspect that variations in the volume of specific brain structures can be observed in children that have OCD. It has not been determined if delayed-maturation of this frontal circuitry contributes to the development of OCD or if OCD is the ailment that inhibits normal growth of structures in the frontal striatal, frontal cortex, or striatum. However, the use of neuroimaging has equipped researchers with evidence of some brain structures that are consistently less adequate and less matured in patients diagnosed with OCD in comparison to brains without OCD. More specifically, structures such as the caudate nucleus, volumes of gray matter, white matter, and the cingulate have been identified as being less developed in people with OCD in comparison to individuals that do not have OCD. However, the cortex volume of the operculum (brain) is larger and OCD patients are also reported to have larger temporal lobe volumes; which has been identified in some women patients with OCD. Further research is needed to determine the effect of these structural size differences on the onset and degree of OCD and the maturation of specific brain structures.
Jonathan Stuart Abramowitz is an American clinical psychologist and Professor in the Department of Psychology and Neuroscience at the University of North Carolina at Chapel Hill (UNC-CH). He is an expert on obsessive-compulsive disorder (OCD) and anxiety disorders whose work is highly cited. He maintains a research lab and currently serves as the Director of the UNC-CH Clinical Psychology PhD Program. Abramowitz approaches the understanding and treatment of psychological problems from a cognitive-behavioral perspective.
Decoupling is a behavioral self-help intervention for body-focused and related behaviors (DSM-5) such as trichotillomania, onychophagia, skin picking and lip-cheek biting. The user is instructed to modify the original dysfunctional behavioral path by performing a counter-movement shortly before completing the self-injurious behavior. This is intended to trigger an irritation, which enables the person to detect and stop the compulsive behavior at an early stage. A systematic review from 2012 suggested some efficacy of decoupling, which was corroborated by Lee et al. in 2019. Whether or not the technique is superior to other behavioral interventions such as habit reversal training awaits to be tested. Decoupling is a variant of habit reversal training.
Even though studies have been conducted on the mouse Hoxb8 gene, no studies have directly investigated the HOXB8 gene in humans concerning TTM or ED.