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{{Short description|Compulsive habit of biting one's fingernails}}
'''Nail biting''' is the habit of [[biting]] one's [[fingernail]]s or [[toenail]]s during periods of [[nervousness]], [[stress (medicine)|stress]] or [[boredom]]. It can also be a sign of mental or emotional disorder, but is commonly seen in intellectuals. The clinical name for nail biting is '''chronic onychophagia'''.
{{Infobox medical condition (new)
| name = Nail biting
| synonyms =
| image = Nailbitebad.jpg
| caption = Fingernails of a nail-biter.
| pronounce =
| field = [[Pediatrics]], [[psychiatry]]
| symptoms =
| complications =
| onset =
| duration =
| types =
| causes =
| risks = Damaged cuticles, shortened and damaged nails, hangnails, bleeding, etc.
| diagnosis =
| differential =
| prevention =
| treatment =
| medication =
| prognosis =
| frequency =
| deaths =
}}


'''Nail biting''', also known as '''onychophagy''' or '''onychophagia''', is an [[human mouth|oral]] [[body-focused repetitive behavior|compulsive]] and unhygienic [[habit]] of biting one's [[Nail (anatomy)|fingernails]]. It is sometimes described as a [[parafunctional activity]], the common use of the mouth for an activity other than speaking, eating, or drinking.
It occurs in:
* 28% to 33% of children ages 7-10 years old,
* 44% of adolescents,
* 19% to 29% of young adults and
* 5% of older adults
*It is more common in boys


Nail biting is very common, especially amongst children, of which 25–35 percent bite nails. More pathological forms of nails biting are considered an [[impulse control disorder]] in the [[DSM-IV|DSM-IV-R]] and are classified under obsessive-compulsive and related disorders in the [[DSM-5]]. The ICD-10 classifies the practice as "other specified behavioral and emotional disorders with onset usually occurring in childhood and adolescence".<ref>{{cite web|title=Impulse control disorder|url=http://ic.steadyhealth.com/impulse_control_disorder.html|publisher=SteadyHealth|access-date=28 April 2012|date=30 December 2010}}</ref> However, not all nail biting is pathological, and the difference between harmful obsession and normal behavior is not always clear.<ref name=pmid23358880>{{cite journal|last1=Ghanizadeh|first1=A|title=Nail biting; etiology, consequences and management.|journal=Iranian Journal of Medical Sciences|date=Jun 2011|volume=36|issue=2|pages=73–9|pmid=23358880|pmc=3556753}}</ref> The earliest reference to nail biting as a symptom of anxiety was in the late sixteenth century in France.<ref>{{Cite book|date=2009|editor-last=Aboujaoude|editor-first=Elias|editor2-last=Koran|editor2-first=Lorrin M.|title=Impulse Control Disorders|doi=10.1017/cbo9780511711930|isbn=9780511711930}}</ref>
==Negative Side-Effects==
Biting the nails can result in the transportation of germs that are buried under the surface of the nail into the mouth. In fact, nail salons use tools that potentially affect a human in a similar way. “If they (nail tools such as files) are used on different people, these tools may spread nail fungi, [[staph]] bacteria or viruses,” warns Rick Lopes, a spokesperson for the California Board of Barbering and Cosmetology. In fact, over 100 bacterial skin infections in 2000 were traced to footbaths in nail salons. Thus, one can see that many pathogens have the ability to "live" inside of a nail, and because of this biting the nails can potentially cause health issues.


== Signs and symptoms ==
Nail biting also has the negative side effect of restraining the use of the hands. A compulsive nailbiter can be restricted in their ability to work(i.e. writing, typing, drawing, driving) because their hand is in their mouth. A person who bites their toenails would be totally incapacitated as well.
Nail biting may lead to harmful effects to the fingers, like infections. These consequences are directly derived from the physical damage of biting or from the hands becoming an infection [[Vector (epidemiology)|vector]]. Moreover, it can also have social consequences, such as withdrawal and avoiding handshakes.<ref name=pmid23358880/>


The ten fingernails are usually equally bitten to approximately the same degree.<ref name="pmid2276242"/> Often, the adjacent skin is bitten off, too, which is called perionychophagia, a special case of [[dermatophagia]]. Biting nails can lead to broken skin on the [[cuticle]]. When cuticles are improperly removed, they are susceptible to microbial and [[virus|viral]] [[infection]]s such as [[paronychia]]. [[Saliva]] may then redden and infect the skin.<ref name=pmid23358880/><ref name="pmid2276242">{{cite journal |vauthors=Leung AK, Robson WL |title=Nailbiting |journal=Clin Pediatr (Phila) |volume=29 |issue=12 |pages=690–2 |year=1990 |pmid=2276242 |doi=10.1177/000992289002901201|s2cid=208874278 }}</ref> In rare cases, fingernails may become severely deformed after years of nail biting due to the destruction of the nail bed.<ref name=pmid23358880/><ref name="pmid16201307">{{cite journal |author=Jabr FI |title=Severe nail deformity. Nail biting may cause multiple adverse conditions |journal=Postgrad Med |volume=118 |issue=3 |pages=37–8, 42 |date=September 2005 |pmid=16201307 |doi=10.3810/pgm.2005.09.1712|s2cid=71984361 }}</ref>
==Breaking the habit==
Various forms of [[aversion therapy]] exist to help people stop biting their nails. These include methods such as coating the nails with a bad-tasting substance (sometimes in the form of a special [[nail polish]]) or wearing a rubber band on their wrist and having friends and family members snap it (or tell the nailbiter to snap it) when they see nailbiting. Some methods (including aforementioned aversion methods) can work by making the biter aware of their actions and finding other things to do. Keeping a record of when one bites may also be helpful in finding the root of the problem.


Nail biting may have an association with oral problems, such as [[gingiva]]l injury, and [[malocclusion]] of the [[anterior teeth]].<ref name=pmid23358880/><ref name="pmid18675214"/> It can also transfer [[pinworm]]s or [[bacteria]] buried under the surface of the nail from the [[Human anus|anus]] region to the [[human mouth|mouth]].<ref name=pmid23358880/> If the bitten-off nails are swallowed, stomach problems can occasionally develop.<ref name="pmid18675214">{{cite journal |vauthors=Tanaka OM, Vitral RW, Tanaka GY, Guerrero AP, Camargo ES |title= Nailbiting, or onychophagia: a special habit |journal=Am J Orthod Dentofacial Orthop |volume=134 |issue=2 |pages=305–8 |date=August 2008 |pmid=18675214 |doi=10.1016/j.ajodo.2006.06.023}}</ref>
Some nail biters who undergo orthodontic treatment find that wearing a [[retainer (orthodontic device)|retainer]] or a bite plate makes it impossible for them to sever their nails with their teeth. This can have the unintentional [[side-effect]] of helping the individual to overcome their nail-biting habit.


Nail-biting can be a source of guilt and shame feelings in the nail biter, a reduced [[quality of life]], and increased [[Social stigma|stigmatization]] in the inner family circles or at a more societal level.<ref name=pmid23358880/><ref name=pmid24535041>{{cite journal|last1=Pacan|first1=P|last2=Reich|first2=A|last3=Grzesiak|first3=M|last4=Szepietowski|first4=JC|title=Onychophagia is Associated with Impairment of Quality of Life.|journal=Acta Dermato-Venereologica|date=Feb 17, 2014|pmid=24535041|doi=10.2340/00015555-1817|volume=94|issue=6|pages=703–6|doi-access=free}}</ref>
Some nailbiters may try [[hypnotherapy]] if other methods fail.


=== Related disorders ===
Some nail-biters, however, find the effectiveness of these remedies to be poor. For them, it may take sheer determination to break the habit. Tactics they may find helpful include making a mental note to stop, promising oneself not to bite, and making it a New Year's resolution to stop.
Other [[body-focused repetitive behavior]]s include [[onychotillomania]] (nail picking), [[excoriation disorder]] (skin picking), [[dermatophagia]] (skin biting), and [[trichotillomania]] (the urge to pull out hair), and all of them tend to coexist with nail biting.<ref name=pmid23358880/><ref name="pmid16402755">{{cite journal |vauthors=Bohne A, Keuthen N, Wilhelm S |title=Pathologic hairpulling, skin picking, and nail biting |journal=Ann Clin Psychiatry |volume=17 |issue=4|pages=227–32 |year=2005 |pmid=16402755 |doi= 10.1080/10401230500295354}}</ref> As an oral parafunctional activity, it is also associated with [[bruxism]] (tooth clenching and grinding), and other habits such as pen chewing and [[morsicatio buccarum|cheek biting]].<ref>{{cite book|vauthors=Cawson RA, Odell EW, Porter S |title=Cawson's essentials of oral pathology and oral medicine.|url=https://archive.org/details/cawsonsessential00caws |url-access=limited |year=2002|publisher=Churchill Livingstone|location=Edinburgh|isbn=0443071063|page=[https://archive.org/details/cawsonsessential00caws/page/n402 66]|edition=7th}}</ref>


In children nail biting most typically co-occurs with [[attention deficit hyperactivity disorder]] (75% of nail biting cases in a study),<ref name=pmid23358880/> and other [[psychiatric disorder]]s including [[oppositional defiant disorder]] (36%) and [[separation anxiety disorder]] (21%).<ref name=pmid23358880/> It is also more common among children and adolescents with [[obsessive–compulsive disorder]].<ref name=pmid23358880/><ref name="pmid20004481">{{cite journal |vauthors=Grant JE, Mancebo MC, Eisen JL, Rasmussen SA |title= Impulse-control disorders in children and adolescents with obsessive–compulsive disorder |journal=Psychiatry Res |volume=175 |issue=1–2 |pages=109–13|date=January 2010 |pmid=20004481 |doi= 10.1016/j.psychres.2009.04.006 |pmc=2815218}}</ref> Nail biting appeared in a study to be more common in men with [[eating disorder]]s than in those without them.<ref name="pmid20571316">{{cite journal |vauthors=Mangweth-Matzek B, Rupp CI, Hausmann A, Gusmerotti S, Kemmler G, Biebl W |title=Eating disorders in men: current features and childhood factors |journal=Eat Weight Disord |volume=15 |issue=1–2 |pages=e15–22 |year=2010 |pmid= 20571316|doi=10.1007/BF03325276 |s2cid=46664252 }}</ref>
Like other nervous habits, nail biting is sometimes a symptom of an emotional problem. In these cases, resolving the underlying problem can help to lessen or eliminate the nail-biting habit.


==Facts==
== Treatment ==
The most common treatment, which is cheap and widely available, is to apply a clear, bitter-tasting [[nail polish]] to the nails. Normally [[denatonium|denatonium benzoate]] is used, the most bitter chemical compound known. The bitter flavor discourages the nail-biting habit.<ref name="pmid8881096">{{cite journal |author=Allen KW |title=Chronic nailbiting: a controlled comparison of competing response and mild aversion treatments |journal=Behav Res Ther |volume=34 |issue=3 |pages=269–72 |date=March 1996 |pmid=8881096 |doi= 10.1016/0005-7967(95)00078-X }}</ref>


[[Behavioral therapy]] is beneficial when simpler measures are not effective. [[Habit reversal training]] (HRT), which seeks to unlearn the habit of nail biting and possibly replace it with a more constructive habit, has shown its effectiveness versus placebo in children and adults.<ref>{{cite journal|last=Bate|first=KS|author2=Malouff, JM |author3=Thorsteinsson, ET |author4= Bhullar, N |title=The efficacy of habit reversal therapy for tics, habit disorders, and stuttering: a meta-analytic review.|journal=Clinical Psychology Review|date=July 2011|volume=31|issue=5|pages=865–71|doi=10.1016/j.cpr.2011.03.013|pmid=21549664}}</ref> A study in children showed that results with HRT were superior to either no treatment at all or the manipulation of objects as an alternative behavior, which is another possible approach to treatment.<ref name=pmid24130603>{{cite journal|last1=Ghanizadeh|first1=A|last2=Bazrafshan|first2=A|last3=Firoozabadi|first3=A|last4=Dehbozorgi|first4=G|title=Habit Reversal versus Object Manipulation Training for Treating Nail Biting: A Randomized Controlled Clinical Trial.|journal=Iranian Journal of Psychiatry|date=Jun 2013|volume=8|issue=2|pages=61–7|pmid=24130603|pmc=3796295}}</ref> In addition to HRT, [[stimulus control]] therapy is used to both identify and then eliminate the stimulus that frequently triggers biting urges.<ref name="Penzel">{{cite web |url=http://westsuffolkpsych.homestead.com/skinpicking.html |title=Skin picking and nail biting: related habits |access-date=2008-03-22 |last= Penzel |first=Fred |publisher=Western Suffolk Psychological Services}}</ref> Other behavioral techniques that have been investigated with preliminary positive results are [[self-help]] techniques, such as [[Decoupling for body-focused repetitive behaviors|decoupling]]<ref>{{Cite journal|last1=Sarris|first1=Jerome|last2=Camfield|first2=David|last3=Berk|first3=Michael|date=2012|title=Complementary medicine, self-help, and lifestyle interventions for Obsessive Compulsive Disorder (OCD) and the OCD spectrum: A systematic review|url=https://linkinghub.elsevier.com/retrieve/pii/S0165032711002187|journal=Journal of Affective Disorders|language=en|volume=138|issue=3|pages=213–221|doi=10.1016/j.jad.2011.04.051|pmid=21620478}}</ref> and the use of wristbands as non-removable reminders.<ref>{{cite journal|last1=Koritzky|first1=G|last2=Yechiam|first2=E|title=On the value of nonremovable reminders for behavior modification: an application to nail-biting (onychophagia).|journal=Behavior Modification|date=Nov 2011|volume=35|issue=6|pages=511–30|pmid=21873368|doi=10.1177/0145445511414869|s2cid=16277609}}</ref> More recently, technology companies have begun producing wearable devices and smart watch applications that track the position of users' hands but no research has been published so far.{{Citation needed|date=January 2022}}
*Nail biting is, according to [[Sigmund Freud|Freudian]] theory, a symptom of [[oral fixation]].
*It is considered to be a mildly embarrassing habit in some cultures.


Another treatment for chronic nail biters is the usage of a dental deterrent device that prevents the front teeth from damaging the nails and the surrounding cuticles. After about two months, the device leads to a full oppression of the nail biting urge.<ref>{{Citation|last=Davinroy|first=Donald L.|title=Nail biting deterrent device and method|date=Oct 2, 2008|url=https://patents.google.com/patent/US20080236600|access-date=2016-09-29}}</ref>


Evidence on the efficacy of drugs is very limited, and they are not routinely used.<ref name=pmid23651231/> A small [[Blind experiment#Double-blind trials|double-blind]] [[Sampling (statistics)|randomized]] [[clinical trial]] in children and adolescents indicated that N-[[acetylcysteine]], a [[glutathione]] and [[glutamate]] modulator, could, in the short term only, be more effective than placebo in decreasing the nail-biting behavior.<ref name=pmid23651231>{{cite journal|last1=Ghanizadeh|first1=A|last2=Derakhshan|first2=N|last3=Berk|first3=M|title=N-acetylcysteine versus placebo for treating nail biting, a double blind randomized placebo controlled clinical trial.|journal=Anti-Inflammatory & Anti-Allergy Agents in Medicinal Chemistry|date=2013|volume=12|issue=3|pages=223–8|pmid=23651231|doi=10.2174/1871523011312030003}}</ref>
[[Category:Habits]]
[[da:Bide negle]]
[[de:Fingernägelkauen]]


[[Artificial nails|Nail cosmetics]] can help to ameliorate nail biting social effects.<ref name="pmid17348997">{{cite journal |vauthors=Iorizzo M, Piraccini BM, Tosti A |title=Nail cosmetics in nail disorders |journal=J Cosmet Dermatol |volume=6 |issue=1 |pages=53–8 |date=March 2007 |pmid=17348997 |doi=10.1111/j.1473-2165.2007.00290.x|s2cid=40739671 }}</ref>
==External links==
*[http://www.breakingthehabits.com/latest/nailbiting.html Stop Nail Biting Free eBook]


Independently of the method used, parental education is useful in the case of young nail biters to maximize the efficacy of the treatment programs, as some behaviors by the parents or other family members may be helping to perpetuate the problem.<ref name=pmid23358880/> For example, punishments have been shown not to be better than placebo, and in some cases may even increase the nail biting frequency.<ref name=pmid23358880/>


== Epidemiology ==
[[da:Løgn]]
[[File:Onychophagia.jpg|thumb|157x157px|Onychophagia]]
[[de:Lüge]]
While it is rare before the age of three,<ref name=pmid23358880/> about 30 percent of children between seven and 10 years of age and 45 percent of [[teenager]]s engage in nail biting.<ref name=pmid23358880/><ref name="pmid2276242"/> Finally, prevalence decreases in adults.<ref name=pmid23358880/> Figures may vary between studies, and could be related to geographic and cultural differences.<ref name=pmid23358880/> The proportion of subjects that have ever had the habit ([[Prevalence#Lifetime prevalence|lifetime prevalence]]) may be much higher than the proportion of current nail-biters ([[Prevalence#Point prevalence|time-point prevalence]]).<ref>{{cite journal|last1=Pacan|first1=P|last2=Grzesiak|first2=M|last3=Reich|first3=A|last4=Kantorska-Janiec|first4=M|last5=Szepietowski|first5=JC|title=Onychophagia and onychotillomania: prevalence, clinical picture and comorbidities.|journal=Acta Dermato-Venereologica|date=Jan 2014|volume=94|issue=1|pages=67–71|pmid=23756561|doi=10.2340/00015555-1616|doi-access=free}}</ref> Although there does not seem to be a gender correlation, results of epidemiological studies on this issue are not fully consistent.<ref name=pmid23358880/> It may be under-recognized since individuals tend to deny or be ignorant of its negative consequences, complicating its diagnosis.<ref name="pmid16402755"/> Having a parent with a mental disorder is also a [[risk factor]].<ref name=pmid23358880/>
[[es:Mentira]]
==References==
[[eo:Mensogo]]
{{Reflist}}
[[fr:Mensonge]]

[[id:Bohong]]
== External links ==
[[hu:Hazugság]]
{{Medical resources
[[nl:Leugen]]
| DiseasesDB =31465
[[ja:嘘]]
| ICD10 = {{ICD10|F|98|8|f|90}} ([[ILDS]] F98.810)
[[pt:Mentira]]
| ICD9 = {{ICD9|307.9}}
[[ru:Ложь]]
| ICDO =
[[sv:Lögn]]
| OMIM =
| MedlinePlus =
| eMedicineSubj =
| eMedicineTopic =
| MeshID=D009259
}}
* {{Commons category-inline|Onychophagia}}

{{Emotional and behavioral disorders}}
{{Mental and behavioural disorders|selected = adult}}

[[Category:Body-focused repetitive behavior]]
[[Category:Conditions of the skin appendages]]
[[Category:Fingers]]
[[Category:Habit and impulse disorders]]
[[Category:Nails (anatomy)]]
[[Category:Neurocutaneous conditions]]
[[Category:Pica (disorder)]]
[[Category:Biting]]

Latest revision as of 15:58, 11 November 2024

Nail biting
Fingernails of a nail-biter.
SpecialtyPediatrics, psychiatry
Risk factorsDamaged cuticles, shortened and damaged nails, hangnails, bleeding, etc.

Nail biting, also known as onychophagy or onychophagia, is an oral compulsive and unhygienic habit of biting one's fingernails. It is sometimes described as a parafunctional activity, the common use of the mouth for an activity other than speaking, eating, or drinking.

Nail biting is very common, especially amongst children, of which 25–35 percent bite nails. More pathological forms of nails biting are considered an impulse control disorder in the DSM-IV-R and are classified under obsessive-compulsive and related disorders in the DSM-5. The ICD-10 classifies the practice as "other specified behavioral and emotional disorders with onset usually occurring in childhood and adolescence".[1] However, not all nail biting is pathological, and the difference between harmful obsession and normal behavior is not always clear.[2] The earliest reference to nail biting as a symptom of anxiety was in the late sixteenth century in France.[3]

Signs and symptoms

[edit]

Nail biting may lead to harmful effects to the fingers, like infections. These consequences are directly derived from the physical damage of biting or from the hands becoming an infection vector. Moreover, it can also have social consequences, such as withdrawal and avoiding handshakes.[2]

The ten fingernails are usually equally bitten to approximately the same degree.[4] Often, the adjacent skin is bitten off, too, which is called perionychophagia, a special case of dermatophagia. Biting nails can lead to broken skin on the cuticle. When cuticles are improperly removed, they are susceptible to microbial and viral infections such as paronychia. Saliva may then redden and infect the skin.[2][4] In rare cases, fingernails may become severely deformed after years of nail biting due to the destruction of the nail bed.[2][5]

Nail biting may have an association with oral problems, such as gingival injury, and malocclusion of the anterior teeth.[2][6] It can also transfer pinworms or bacteria buried under the surface of the nail from the anus region to the mouth.[2] If the bitten-off nails are swallowed, stomach problems can occasionally develop.[6]

Nail-biting can be a source of guilt and shame feelings in the nail biter, a reduced quality of life, and increased stigmatization in the inner family circles or at a more societal level.[2][7]

[edit]

Other body-focused repetitive behaviors include onychotillomania (nail picking), excoriation disorder (skin picking), dermatophagia (skin biting), and trichotillomania (the urge to pull out hair), and all of them tend to coexist with nail biting.[2][8] As an oral parafunctional activity, it is also associated with bruxism (tooth clenching and grinding), and other habits such as pen chewing and cheek biting.[9]

In children nail biting most typically co-occurs with attention deficit hyperactivity disorder (75% of nail biting cases in a study),[2] and other psychiatric disorders including oppositional defiant disorder (36%) and separation anxiety disorder (21%).[2] It is also more common among children and adolescents with obsessive–compulsive disorder.[2][10] Nail biting appeared in a study to be more common in men with eating disorders than in those without them.[11]

Treatment

[edit]

The most common treatment, which is cheap and widely available, is to apply a clear, bitter-tasting nail polish to the nails. Normally denatonium benzoate is used, the most bitter chemical compound known. The bitter flavor discourages the nail-biting habit.[12]

Behavioral therapy is beneficial when simpler measures are not effective. Habit reversal training (HRT), which seeks to unlearn the habit of nail biting and possibly replace it with a more constructive habit, has shown its effectiveness versus placebo in children and adults.[13] A study in children showed that results with HRT were superior to either no treatment at all or the manipulation of objects as an alternative behavior, which is another possible approach to treatment.[14] In addition to HRT, stimulus control therapy is used to both identify and then eliminate the stimulus that frequently triggers biting urges.[15] Other behavioral techniques that have been investigated with preliminary positive results are self-help techniques, such as decoupling[16] and the use of wristbands as non-removable reminders.[17] More recently, technology companies have begun producing wearable devices and smart watch applications that track the position of users' hands but no research has been published so far.[citation needed]

Another treatment for chronic nail biters is the usage of a dental deterrent device that prevents the front teeth from damaging the nails and the surrounding cuticles. After about two months, the device leads to a full oppression of the nail biting urge.[18]

Evidence on the efficacy of drugs is very limited, and they are not routinely used.[19] A small double-blind randomized clinical trial in children and adolescents indicated that N-acetylcysteine, a glutathione and glutamate modulator, could, in the short term only, be more effective than placebo in decreasing the nail-biting behavior.[19]

Nail cosmetics can help to ameliorate nail biting social effects.[20]

Independently of the method used, parental education is useful in the case of young nail biters to maximize the efficacy of the treatment programs, as some behaviors by the parents or other family members may be helping to perpetuate the problem.[2] For example, punishments have been shown not to be better than placebo, and in some cases may even increase the nail biting frequency.[2]

Epidemiology

[edit]
Onychophagia

While it is rare before the age of three,[2] about 30 percent of children between seven and 10 years of age and 45 percent of teenagers engage in nail biting.[2][4] Finally, prevalence decreases in adults.[2] Figures may vary between studies, and could be related to geographic and cultural differences.[2] The proportion of subjects that have ever had the habit (lifetime prevalence) may be much higher than the proportion of current nail-biters (time-point prevalence).[21] Although there does not seem to be a gender correlation, results of epidemiological studies on this issue are not fully consistent.[2] It may be under-recognized since individuals tend to deny or be ignorant of its negative consequences, complicating its diagnosis.[8] Having a parent with a mental disorder is also a risk factor.[2]

References

[edit]
  1. ^ "Impulse control disorder". SteadyHealth. 30 December 2010. Retrieved 28 April 2012.
  2. ^ a b c d e f g h i j k l m n o p q r s Ghanizadeh, A (Jun 2011). "Nail biting; etiology, consequences and management". Iranian Journal of Medical Sciences. 36 (2): 73–9. PMC 3556753. PMID 23358880.
  3. ^ Aboujaoude, Elias; Koran, Lorrin M., eds. (2009). Impulse Control Disorders. doi:10.1017/cbo9780511711930. ISBN 9780511711930.
  4. ^ a b c Leung AK, Robson WL (1990). "Nailbiting". Clin Pediatr (Phila). 29 (12): 690–2. doi:10.1177/000992289002901201. PMID 2276242. S2CID 208874278.
  5. ^ Jabr FI (September 2005). "Severe nail deformity. Nail biting may cause multiple adverse conditions". Postgrad Med. 118 (3): 37–8, 42. doi:10.3810/pgm.2005.09.1712. PMID 16201307. S2CID 71984361.
  6. ^ a b Tanaka OM, Vitral RW, Tanaka GY, Guerrero AP, Camargo ES (August 2008). "Nailbiting, or onychophagia: a special habit". Am J Orthod Dentofacial Orthop. 134 (2): 305–8. doi:10.1016/j.ajodo.2006.06.023. PMID 18675214.
  7. ^ Pacan, P; Reich, A; Grzesiak, M; Szepietowski, JC (Feb 17, 2014). "Onychophagia is Associated with Impairment of Quality of Life". Acta Dermato-Venereologica. 94 (6): 703–6. doi:10.2340/00015555-1817. PMID 24535041.
  8. ^ a b Bohne A, Keuthen N, Wilhelm S (2005). "Pathologic hairpulling, skin picking, and nail biting". Ann Clin Psychiatry. 17 (4): 227–32. doi:10.1080/10401230500295354. PMID 16402755.
  9. ^ Cawson RA, Odell EW, Porter S (2002). Cawson's essentials of oral pathology and oral medicine (7th ed.). Edinburgh: Churchill Livingstone. p. 66. ISBN 0443071063.
  10. ^ Grant JE, Mancebo MC, Eisen JL, Rasmussen SA (January 2010). "Impulse-control disorders in children and adolescents with obsessive–compulsive disorder". Psychiatry Res. 175 (1–2): 109–13. doi:10.1016/j.psychres.2009.04.006. PMC 2815218. PMID 20004481.
  11. ^ Mangweth-Matzek B, Rupp CI, Hausmann A, Gusmerotti S, Kemmler G, Biebl W (2010). "Eating disorders in men: current features and childhood factors". Eat Weight Disord. 15 (1–2): e15–22. doi:10.1007/BF03325276. PMID 20571316. S2CID 46664252.
  12. ^ Allen KW (March 1996). "Chronic nailbiting: a controlled comparison of competing response and mild aversion treatments". Behav Res Ther. 34 (3): 269–72. doi:10.1016/0005-7967(95)00078-X. PMID 8881096.
  13. ^ Bate, KS; Malouff, JM; Thorsteinsson, ET; Bhullar, N (July 2011). "The efficacy of habit reversal therapy for tics, habit disorders, and stuttering: a meta-analytic review". Clinical Psychology Review. 31 (5): 865–71. doi:10.1016/j.cpr.2011.03.013. PMID 21549664.
  14. ^ Ghanizadeh, A; Bazrafshan, A; Firoozabadi, A; Dehbozorgi, G (Jun 2013). "Habit Reversal versus Object Manipulation Training for Treating Nail Biting: A Randomized Controlled Clinical Trial". Iranian Journal of Psychiatry. 8 (2): 61–7. PMC 3796295. PMID 24130603.
  15. ^ Penzel, Fred. "Skin picking and nail biting: related habits". Western Suffolk Psychological Services. Retrieved 2008-03-22.
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