Review

Behavioral treatment of chronic skin-picking in individuals withdevelopmental disabilities: A systematic review

Russell Lang a,*, Robert Didden b, Wendy Machalicek c, Mandy Rispoli d, Jeff Sigafoos e,Giulio Lancioni f, Austin Mulloy g, April Regester a, Nigel Pierce g, Soyeon Kang g

a The Eli and Edythe L. Broad Center for Asperger Research, University of California at Santa Barbara, USAb Radboud University Nijmegen, The Netherlandsc University of Wisconsin-Madison, USAd Texas A&M University, College Station, USAe Victoria University of Wellington, New Zealandf University of Bari, Italyg The Meadows Center for Preventing Educational Risk, The University of Texas at Austin, USA

Contents

1. Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306

1.1. Search procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306

1.2. Inclusion and exclusion criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306

1.3. Data extraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306

1.4. Inter-rater agreement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311

Research in Developmental Disabilities 31 (2010) 304–315

A R T I C L E I N F O

Article history:

Received 30 September 2009

Accepted 27 October 2009

Keywords:

Self-excoriation

Skin-picking

Self-injury

Developmental disability

Autism

Prader–Willi

Systematic review

A B S T R A C T

Skin-picking is a type of self-injurious behavior involving the pulling, scratching, lancing,

digging, or gouging of one’s own body. It is associated with social impairment, and

increased medical and mental health concerns. While there are several reports showing

that skin-picking is common in individuals with developmental disabilities, knowledge

about effective treatment approaches is sparse. We therefore reviewed studies involving

the treatment of chronic skin-picking in individuals with developmental disabilities.

Systematic searches of electronic databases, journals, and reference lists identified

16 studies meeting the inclusion criteria. These studies were evaluated in terms of: (a)

participants, (b) functional assessment procedures and results, (c) intervention

procedures, (d) results of the intervention, and (e) certainty of evidence. Across the 16

studies, intervention was provided to a total of 19 participants aged 6–42 years. Functional

assessment procedures included direct observations, analog functional analyses, and

functional assessment interviews. The most commonly identified function was automatic

reinforcement. Treatment approaches included combinations of differential reinforce-

ment, providing preferred items and activities stimuli (e.g., toys), wearing protective

clothing (e.g., helmets or gloves), response interruption and redirection, punishment, and

extinction. Improvements in behavior were reported in all of the reviewed studies.

Suggestions for future intervention research are offered.

� 2009 Elsevier Ltd. All rights reserved.

* Corresponding author at: The Eli & Edythe L. Broad Asperger Research Center, Koegel Autism Center, Graduate School of Education, UC Santa Barbara, CA

93106-9490, USA. Tel.: +1 254 716 1508.

E-mail address: russlang@education.ucsb.edu (R. Lang).

Contents lists available at ScienceDirect

Research in Developmental Disabilities

0891-4222/$ – see front matter � 2009 Elsevier Ltd. All rights reserved.

doi:10.1016/j.ridd.2009.10.017

2. Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311

2.1. Participants. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311

2.2. Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311

2.3. Functional assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311

2.4. Intervention procedures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312

2.5. Outcomes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313

2.6. Certainty of evidence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313

3. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 314

Skin-picking (also called neurotic excoriation, psychogenic excoriation, dermatotillomania, or self-excoriation) is arepetitive self-injurious behavior involving the pulling, scratching, lancing, digging, or gouging of one’s own body usingfingers or tools (e.g., paper clip or tweezers) in the absence of a relevant dermatological condition (Arnold, Auchenbach, &McElroy, 2001; Deckersbach, Wilhelm, Keuthen, Baer, & Jenike, 2002; Hayes, Storch, & Berlanga, 2009). A wide array ofbehavioral topographies and patterns are associated with skin-picking. However, the most common body areas affected arethose which are easily reached (e.g., facial features) (Arnold et al., 1998). Some individuals engage in skin-picking brieflymultiple times a day and others engage in episodes of skin-picking which may last for hours (Arnold et al., 2001).

Studies have examined the prevalence of skin-picking in individuals without disabilities and individuals withdevelopmental disabilities. Among a sample of non-disabled adults (n = 345) Hayes et al. (2009) found that up to 63%engaged in some form of skin-picking and 5.4% reported severe levels of skin-picking behavior. Prevalence of skin-picking iscommonly higher in samples of individuals with developmental disabilities, such as Prader–Willi syndrome (Didden,Korzilius, & Curfs, 2007) and Smith–Magenis syndrome (Edelman et al., 2007). For example, Didden et al. (2007) found thatskin-picking was present in as many as 85% of a sample of 119 children and adults with Prader–Willi syndrome.

Skin-picking has been directly associated with social, occupational, and academic impairment, increased medical andmental health concerns (i.e., anxiety, depression, obsessive–compulsive disorder) (Didden et al., 2007; Hayes et al., 2009;Odlaug & Grant, 2008), and financial burden (Flessner & Woods, 2006; Hayes et al., 2009). Additionally, many individualswho engage in skin-picking report feelings of shame, guilt, and embarrassment because of visible scars, open sores, andwounds (Deckersbach et al., 2002; Didden, Proot, Lancioni, Van Os, & Curfs, 2008). Concern regarding personal appearancecan be severe enough to warrant diagnosis of body dismorphic disorder (BDD; Phillips & Taub, 1995). Skin-picking inchildren with developmental disabilities has been reported to result in severe tissue damage, scars, ulcerations, andinfections (e.g., Hyman, Fisher, Mercugliano, & Cataldo, 2001). When areas around and within the eyes or rectum are targeted(often called eye gouging and rectal digging) blindness and prolapsed rectum have been reported (e.g., Heidorn & Jensen,1984; Stokes & Luiselli, 2009).

Arnold et al. (2001) reviewed 18 studies involving the pharmacological treatment of skin-picking and found that selectiveserotonin reuptake inhibitors, doxepin, clomipramine, naltrexone, pimozide, and olanzapine may be effective in reducingskin-picking. However, methodological limitations across pharmacological studies (e.g., no large double-blind studies)preclude definitive statements regarding the effects of pharmacological treatment. Shapira, Lessig, Murphy, Driscoll, andGoodman (2002) evaluated the use of Topiramate (an anti-epileptic medication) on the skin-picking behavior of three adultswith Prader–Willi syndrome. In an 8-week-open-label trial, Topiramate was found to reduce skin-picking enough for lesionsto heal. However, the mechanism by which Topiramate reduces skin-picking in Prader–Willi is still unknown and double-blind studies are therefore warranted.

Another treatment option is behavioral intervention. A small number of studies have investigated behavioral treatments forskin-picking in individuals without disabilities (Hayes et al., 2009). Specifically, Twohig and Woods (2001) reported theeffectiveness of habit reversal in reducing skin-picking in two adolescents. Treatment was implemented in 1-h sessions andconsisted of awareness enhancement and competing response training. The competing response involved the participantsmaking a closed fist for 1 min contingent on picking or an antecedent stimulus associated with picking. Positive results withhabit reversal were also reported by Teng, Woods, and Twohig (2006) in the treatment of skin-picking exhibited by 19 femaleadults. Finally, Deckersbach et al. (2002) reported positive results of a cognitive–behavioral approach that included habitreversal.

However, it is an empirical question as to whether behavioral treatments alone would be effective in the treatment ofskin-picking among individuals with developmental disabilities. For example, individuals with autism spectrum disordersmay lack the communicative or cognitive ability to participate fully in cognitive–behavioral therapy (Lang et al., in press).Given the prevalence of skin-picking in individuals with developmental disabilities and the potential of skin-picking toexacerbate other medical and mental health concerns associated with developmental disabilities, a systematic review ofbehavioral treatments of skin-picking for this population is warranted.

To facilitate evidence-based practice in this important area, we herein provide a systematic review of studies on thebehavioral treatment of skin-picking among individuals with developmental disabilities. The objective of this review is todescribe the characteristics of these studies (e.g., participants, assessment procedures, intervention procedures), evaluateintervention outcomes, and appraise the certainty of the evidence for the existing corpus of intervention studies. A review ofthis type is primarily intended to guide and inform practitioners in the assessment and treatment of skin-picking inindividuals with developmental disabilities. A secondary aim is to identify gaps in the existing database so as to stimulate

R. Lang et al. / Research in Developmental Disabilities 31 (2010) 304–315 305

future research efforts aimed at developing new and more effective assessments and interventions for this debilitating andharmful behavior.

1. Method

This review involved a systematic analysis of studies that focused on the treatment of skin-picking in individuals withdevelopmental disabilities. Each study that met pre-determined inclusion criteria was analyzed and summarized in termsof: (a) participants, (b) functional assessment procedures and results, (c) intervention procedures, (d) results of intervention,and (e) certainty of evidence. To assess the certainty of evidence, we critically appraised each study’s design and relatedmethodological details (e.g., procedural descriptions and reliability of data).

1.1. Search procedures

Systematic searches were conducted in four electronic databases: Education Resources Information Center (ERIC),MEDLINE, Psychology and Behavioral Sciences Collection, and PsychINFO. Publication year was not restricted, but the searchwas limited to English-language peer-reviewed studies. On all four databases, the terms ‘‘excoriation’’, ‘‘picking’’, ‘‘gouging’’,‘‘lancing’’, ‘‘scratching’’, ‘‘self-injury’’ plus either ‘‘developmental disability’’, ‘‘autism’’, ‘‘mental retardation’’, ‘‘intellectualdisability’’, ‘‘developmental disorder’’, or ‘‘syndrome’’ were inserted as free-text terms into the keyword search field. Thisinitial search yielded a sample of 223 studies. The abstracts of the 223 studies were reviewed to identify studies for inclusion(see Section 1.2). The reference lists for studies meeting these criteria were also reviewed to identify additional articles forpossible inclusion. Hand searches, covering January to September 2009, were then completed for the journals that hadpublished the included studies to identify recent studies that would not yet be listed in aforementioned databases. Finally, alist of authors publishing studies regarding skin-picking was created and each of these names was searched individually toidentify other potentially relevant work from the researchers in this area. This systematic search occurred during August andSeptember 2009.

1.2. Inclusion and exclusion criteria

To be included in this review articles had to meet two inclusion criteria. First, operational definitions of skin-picking hadto involve the use of fingers or a hand-held object (e.g., pen or paper clip) to self inflict tissue damage by pulling, scratching,lancing, digging, or gouging anywhere on the body, including inside the eye socket, mouth, nose, and rectum. Second, thearticle had to contain a behavioral intervention for skin-picking for at least one person with a developmental disability (e.g.,autism spectrum disorder, Prader–Willi syndrome, intellectual disability). Behavioral intervention was defined as theimplementation of one or more therapeutic or educational procedures involving the manipulation of environmentalantecedents (triggers) or consequences (reinforcement or punishment). Studies that focused only on assessment,description, or prevalence of skin-picking were not included (e.g., Arnold et al., 2001; Didden et al., 2007; Flessner & Woods,2006; Hayes et al., 2009; Keuthen, Wilhelm, et al., 2001; Keuthen, Deckersbach, et al., 2001; Odlaug & Grant, 2008). Studiescontaining only medication treatments with no behavioral intervention components were also excluded (e.g., Sandmanet al., 2007; Shapira, Lessig, Lewis, Goodman, & Driscoll, 2004). The end result was the identification of 16 studies that metthe inclusion criteria.

1.3. Data extraction

Each identified study was first assessed to determine if it met the inclusion criteria. After this, each included study wassummarized in terms of the following features: (a) participant characteristics, (b) assessment procedures and results, (c)intervention procedures, (d) results of the intervention, and (e) certainty of evidence. Various procedural aspects were alsonoted, including experimental design, inter-observer agreement, implementation setting, and maintenance of effects. Mainfindings were summarized in terms of the extent to which participants were reported to have shown a decrease in somedimension of skin-picking (e.g., frequency or intensity) or in some measure of tissue damage (e.g., number of open sores).Because none of the included studies contained group designs, main findings were summarized for the single-caseexperimental designs by calculating the percentage of non-overlapping data (PND; Scruggs, Mastropieri, & Casto, 1987).Certainty of evidence was evaluated by considering main findings in light of the research design and other methodologicaldetails. The ability of a study to provide certainty of evidence was rated as either ‘‘inconclusive’’ or ‘‘conclusive’’ (Millar, Light,& Schlosser, 2006). This classification system was used in this review in an effort to provide an overview of the quality ofevidence across the corpus of reviewed studies (Schlosser & Sigafoos, 2007).

Appraising the certainty of evidence followed a two-stage process. First, only studies that included an experimentaldesign (e.g., multiple baseline or ABAB) could be considered as having the potential to provide conclusive evidence. Thus anystudy that lacked a recognized experimental design was automatically classified as providing inconclusive results. Thisincluded descriptive studies and studies using A–B or intervention-only designs. Second, studies that employed anexperimental design also had to meet four additional standards to be classified as providing conclusive evidence. First, thedata had to provide a convincing demonstration of an intervention effect. This determination was based on visual inspection

R. Lang et al. / Research in Developmental Disabilities 31 (2010) 304–315306

Table 1

Summary of reviewed studies.

Citation Participant characteristics Functional Assessment

Procedures: results

Intervention procedures Results and certainty of evidence

Azrin et al. (1975) 2 females, 26 and 32 years old,profound intellectual disability

NRa DRIb: Reinforced for postures incompatible withskin-picking or eye gouging (i.e., hands at side)

Results: Skin-picking and eye gougingreduced (PNDc = 100%) also noted increasesin social interactions and responsiveness

Engaged in skin scratching andeye gouging that resulted inswelling, scabs, and open sores

Inconclusive: AB design

Blankenship andLambarts (1989)

1 female, 42 years old, profoundintellectual disability

Narrative ABCd descriptions:Automatic reinforcement

Contingent helmet restraint: A hard plastic helmet with abubble-like face shield and retention strap to prevent

removal by participant was placed on participantcontingent upon cheek gouging for 5 min

Results: Cheek gouging reduced from Mf of21 to M of 1.6 occurrences per hour

(PND = 100%). Effects were maintained for 6months

Engaged in cheek gouging thatresulted in two round openlesions

DROe: Starting with 3 min and gradually increasing to30 min over 2 days using praise and edibles as reinforcers

Conclusive: ABAB design, M IOA> 80%, andclinically significant improvement

Conley andWolery (1980)

1 female, 7 years old, profoundintellectual disability andblindness

NR Overcorrection: Contingent upon eye gouging, thetherapist said, ‘‘No’’ and 5 min of arm exercise wasrequired

Results: Eye gouging reduced from M of 12occurrences per session to M< 3occurrences (PND = 100%). Effects weremaintained at 30 weeks

Engaged in skin-picking aroundand within eye socket

Inconclusive: AB design

Dorsey et al. (1980) 1 female, 25 years old, profoundintellectual disability

NR Punishment: Water mist sprayed in face Results: Skin tearing reduced from M of 50%of intervals to M< 10% of intervals

(PND = 100%)Engaged in skin tearing resultingin removal of flesh from lips andforearms

Conclusive: ABAB design, M IOA> 80%, andclinically significant improvement

Dorsey et al. (1982) 1 male and 1 female, 14 and 16years old, severe intellectualdisability

NR DRO: Reinforced appropriate toy play on a 30 s fixedinterval schedule

Results Experiment 1: Contingent protectiveequipment + DRO was the most effective forboth participants (PND = 100%) across twosettings. Results Experiment 2:Nonprofessional staff implemented theintervention and eye gouging was reduced inboth participants (PND = 100%). Effects were

maintained for 104 days with 1 participant(other participant moved prior to collectionof maintenance data)

Engaged in eye gouging resultingin scar tissue around face and eyes

Verbal reprimand: Stating ‘‘No’’ contingent on eye gouging Conclusive: Experiment 1: MBLg acrosssettings, Experiment 2: MBL acrossparticipants, M IOA in bothexperiments> 80%, clinically significantimprovement

Continuous protective equipment: Padded helmet and foamgloves worn during whole session

Contingent protective equipment: Helmet and gloves wornfor 2 min contingent on eye gouging

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Table 1 (Continued )

Citation Participant characteristics Functional AssessmentProcedures: results

Intervention procedures Results and certainty of evidence

Heidorn andJensen (1984)

1 male, 27 years old, profoundintellectual disability

Analysis of the participant across12 h (2 sessions 6 h each)suggested skin-picking functionedto obtain attention and escapetask demands. However, the exact

procedures used to make thisdetermination were not stated

DRI: Reinforced sitting on hands with attention (verbaland physical) and preferred edibles

Results: Skin-picking was initially reduced toa low frequency following intervention butthen returned to high levels whenmedication dosage was changed and aftermoving to a new residential facility. Low

levels were restored after training the newstaff to implement intervention procedures.This low frequency of skin-picking was thenmaintained for 35 months. PND frombaseline to follow-up at 35 months was100%

Engaged in skin-picking on faceresulting in lose of cartilage innose, a 3 cm� 3.8 cm openwound on forehead, and

blindness in both eyes. Whenrestrained he vigorously rubbedhead against restraints tocontinue self-injury

Escape extinction: Graduated guidance used to preventescape form task demands

Inconclusive: AB design

Ladd et al. (2009) 1 female, 9 years old, autism MASh: Automatic reinforcement Competing activities: Participant was given choice of smallitems (e.g., Koosh Ball �, Silly Puddy �) that he couldmanually manipulate instead of engaging in skin-picking

Results: Skin-picking reduced from M 55% toM 10% (PND = 100%) parents reported themaintenance of effects

Engaged in whole body skin-picking that resulted in multipleopen sores and scars

Conclusive: ABAB design, M IOA> 80%,clinically significant improvement

Lane et al. (2006) 1 male, 9 years old, ADHDi,borderline intellectual disability

(IQ = 77), and a speech languagedelay

Functional assessment interview:Automatic reinforcement

Competing activities: Participant was given choice of smallitems (e.g., malleable plastic shapes) that she could

manually manipulate instead of engaging inskin-picking

Results: Competing activity + Adderallresulted in lower levels of skin-picking

reduced from M 67% to M 15% (PND = 92%).Medication alone and behavioralintervention alone did not result in clinicallysignificant improvement

Engaged in whole body skin-picking with hands and objectsthat resulted in multiple opensores and scars

Narrative ABC descriptions:Automatic reinforcement

Adderall: 10 mg/day Conclusive: ABCBAB design comparedmedication only, competingactivity + medication, and competingactivity only, M IOA> 80%, clinicallysignificant reduction in combined condition

Lang et al. (2009) 1 female, 17 years old, Aspergersyndrome and borderlineintellectual difficulty

Functional assessment interview:Automatic reinforcement

Bandages: Bandages were placed on the participantcovering areas commonly picked to prevent tactile andvisual antecedents and consequences

Results: Number of open sores decreasedfrom M 37 to M 3 (PND = 100%) effectsmaintained after intervention was

withdrawn for 4 monthsEngaged in whole body skin-picking that resulted in multipleopen sores and scars

QABFj: Automatic reinforcement DRI: The participant was given a choice of special dessertsif bandages remained undisturbed between meals

Conclusive: ABAC design, M IOA> 80%,clinically significant improvement

Fading: Reinforcement schedule was gradually reducedand bandages were gradually faded in size until allintervention components were ceased

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Luiselli (1989) 1 male, 18 years old, deaf, severevisual impairment, and moderateintellectual disability

NR Contingent glove wearing: Soft cotton gloves were placedon participant contingent upon skin-picking. Participantput gloves on independently and wore them for 1 min

Results: Skin-picking reduced from 68% ofintervals to 16% of intervals in morning(PND = 100%) and 62% of intervals to 17% inthe afternoon (PND = 100%) effects weremaintained for 6 months

Engaged in skin-picking on handsthat resulted in multiple opensores

DRO: With no specifically programmed time intervalsusing praise

Conclusive: MBL across daily scheduledesign, M IOA> 80%, clinically significantimprovement

Mulick et al. (1978) 1 male, 22 years old, profoundintellectual disability

NR Competing activities: Toys the participant was observedplaying with were made available. Participant was taughtto select toy and exchange old toys for new toys.Reinforcement (praise and edibles) was given contingenton toy exchange

Results: Skin-picking ranged from 0% to 50%of intervals (M = 36%) in baseline and ranged0–25% of intervals (M = 3%) duringintervention. PND could not be calculateddue to a 0 value in baseline

Engaged in skin-picking on handsparticularly around finger tips

Conclusive: ABAB design, M IOA> 80%,clinically significant improvement

Richman et al. (1998) 1 female, 27 years old, profoundintellectual disability

Brief functional analysis:Automatic reinforcement

Escape extinction: Task demands were regardless of skin-picking

Results: After escape extinction was shownto be ineffective, sensory extinction plus

DRA immediately suppressed finger picking(PND = 100%). When DRA alone wasimplemented finger picking increased

Engaged in skin-picking onfingers resulting in multiplelacerations and scabs

DRAk: Praise contingent upon independent toy play Conclusive: Compared the effects of sensoryextinction + DRA (A phase) to DRA alone (Bphase) in an ABAB design, M IOA> 80%,clinically significant improvement design

Sensory extinction: Blocked finger picking by redirectingher hands to toys

Slifer et al. (1984) 1 male, 6 years old, profoundintellectual disability, congenital

rubella syndrome, severe visualimpairment

Analog functional analysis:Automatic reinforcement and

demonstrated less eye gougingwhen play materials wereavailable and therapist providedattention

Response interruption: Contingent upon eye gouging,therapist firmly stated ‘‘No’’ and manually restrained the

participant’s hands for 10 s

Results: Eye gouging was substantiallyreduced (PND = 100%) effects were

maintained for 9 months

Engaged in skin-picking aroundand within eye socket

Competing activities: Participant was given small preferredtoys and prompted by guiding his hands to toys every 15 sMatched stimulation: Bright light source from a 60 W bulbwas shown near the participant’s face in an effort to matchthe hypothesized sensory stimulation obtained via eyegouging

Conclusive: MBL across settings design, M

IOA> 80%, clinically significantimprovement

DRO: Consisting of praise and physical contact wasavailable contingent upon eye gouging, praise was ceased,light source was turned off, and toys were removedDRI: Light source was turned on contingent uponmanipulation of the toysFading: Light source was eventually faded fromintervention by gradually moving the light source awayfrom the participant

Stokes andLuiselli (2009)

1 male, 26 years old, Type IIPrader–Willi syndrome

MAS and FASTl: Attention fromstaff, escape nonpreferredactivities, and automatic

reinforcement as tactilestimulation

Limited access to high probability environment: Rectalpicking occurred most often in the bathroom so bathroomvisits were limited to 5 min

Results: Rectal picking reduced from M 3.8times per week with 90% of incidentsresulting in hospital visit to only 6 times in

30-week period with no hospitalizationrequired (PND = 74%)

Engaged skin-picking aroundrectum that resulted in aprolapsed rectum

Analog functional analysis:Automatic reinforcement andto obtain attention

Functional Communication Training: Participant wastaught to request additional time away from taskdemands when in the bathroom

Inconclusive: AB design with No IOA

DRO: Consisting of praise and small preferred items

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Table 1 (Continued )

Citation Participant characteristics Functional AssessmentProcedures: results

Intervention procedures Results and certainty of evidence

Tiger et al. (2009) 1 male, 19 years old, Aspergersyndrome

Analog functional analysis:Automatic reinforcement

Awareness training: Participant was sat in front ofmirror and prompted to notice when he wasengaging inskin-picking

Results: Skin-picking reduced from M 48% ofintervals in baseline phases to 0% intreatment phases (PND = 100%) both self-monitored intervention and therapistdelivered intervention were effective

Engaged in skin-picking onforehead, hands, mouth, and noseresulting in multiple open soresand scars

Competing response: Involved teaching participant toplace hands in lap or pockets

Conclusive: ABABC design, M IOA> 80%,clinically significant improvement

DRO: Participant earned tokens worth .10 US cents forgradually increasing periods of time without skin-pickingSelf-management: Participant was taught to implementhis own intervention

Wesolowski andZawlocki (1982)

2 female identical twins, 6 yearsold, profound intellectualdisability and blindness

NR Auditory time out: Ear muffs which blocked most soundwere placed on the participants for 2 min contingent uponeye gouging

Results: Experiment 1, For both participantstime out + DRO was the most effectiveintervention combination resulting in theelimination of eye gouging (PND = 100%).Effects were maintained at 2 months.Experiment 2, For both participantsovercorrection + DRO eliminated eye gouging

(PND = 100%)Engaged in eye gouging resultingin bruising and tissue damagearound eyes and in sockets

DRO: Delivery of small quantities of apple juice contingentupon 2 min interval without eye gouging

Inconclusive: Experiment 1, Combinations ofintervention components were compared inan ABACAD design, but possible carry overeffects were not controlled for

Response interruption: Hands were blocked from eyegouging and therapist yelled ‘‘No’’

Conclusive: Experiment 2, MBL acrossparticipants, M IOA> 80%, clinicallysignificant improvement

Overcorrection: Participants were required to perform armexercises for 3–5 min contingent upon eye gouging

a Not reported.b Differential reinforcement of incompatible behavior.c Percent non-overlapping data.d Antecedent behavior consequence.e Differential reinforcement of other behavior.f Mean.g Multiple baseline.h Motivational Assessment Scale.i Attention deficit hyperactivity disorder.j Questions About Behavioral Functions Scale.k Differential reinforcement of alternative behavior.l Functional Analysis Screening Tool.

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of data trends within and across phases using criteria described by Kennedy (2005). For example, there had to be a clinicallysignificant decrease of skin-picking when intervention was introduced. Second, if relevant, there had to be adequate inter-observer agreement data (e.g., agreement observations conducted across 20% of the sessions and agreement at or exceeding80%). Third, the dependent and independent variables had to be operationally defined. And finally, the procedures had to bedescribed in sufficient detail to enable replication.

1.4. Inter-rater agreement

The first, third, fourth, and tenth author made an initial determination as to whether each study identified in the searchmet the inclusion criteria. After this, the seventh through tenth authors repeated the search and independently assessed eachof the studies against the inclusion/exclusion criteria. Agreement as to whether a study should be included or excluded wasobtained on 16 of 17 studies (94%). Rojahn, Schroeder, and Mulick (1980) was originally included in the review, but wassubsequently excluded because a behavioral intervention to reduce skin-picking was not implemented.

The first author extracted information to develop an initial summary of the 16 included studies. The accuracy of thesesummaries was independently checked by one of the remaining co-authors using a checklist that included the initialsummary of the study and a number of questions regarding various details of the study (i.e., Is this an accurate description ofthe participants in terms of age, diagnosis, and sex?, Is this an accurate description of the skin-picking and damage caused?,Is this an accurate description of the functional assessment and results?, Is this an accurate description of interventionprocedures?, Is this an accurate description of the results of intervention?, and Is this an accurate description of the certaintyof evidence?). Co-authors were asked to read the study and the summary and then complete the checklist. In cases where thesummary was not considered accurate, co-authors were asked to edit the summary to improve its accuracy.

This approach was intended to ensure accuracy in the summary of studies, but it also provided a measure of inter-rateragreement on data extraction and analysis. Specifically, there were 96 items on which there could be agreement ordisagreement (i.e., 16 studies with six questions per study). Agreement was obtained on 89 items (93%). In the seveninstances where aspects of the summaries were considered inaccurate, changes were made to more accurately summarizethe studies.

2. Results

Table 1 summarizes the (a) participants, (b) functional assessment procedures and results, (c) intervention procedures,(d) results of the intervention, and (e) certainty of evidence for the 16 included studies.

2.1. Participants

Collectively, the 16 studies provided intervention to a total of 19 participants. Most studies contained only oneparticipant, but three studies contained two participants (Azrin, Gottlieb, Hughart, Wesolowski, & Rahn, 1975; Dorsey, Iwata,Reid, & Davis, 1982; Wesolowski & Zawlocki, 1982). Some studies contained multiple participants, but only one participantfrom each engaged in skin-picking (e.g., Blankenship & Lambarts, 1989). Eight (42%) of the participants were male and 11(58%) were female. The mean age was 18 years (range, 6–42). Participants were diagnosed with various types of disabilities,including profound intellectual disability (n = 10), severe intellectual disability (n = 2) moderate intellectual disability (n = 1),borderline intellectual disability (n = 2), autism (n = 1), ADHD (n = 1), sensory impairment (i.e., vision or hearing) (n = 4),Asperger’s syndrome (n = 2), congenital rubella syndrome (n = 1), and Prader–Willi (n = 1). Five participants had multipledisabilities.

The participants targeted multiple body locations when engaging in skin-picking including cheeks, hands, rectum, eyesocket, forehead, mouth, and nose. Three studies reported skin-picking covering the whole body (Ladd, Luiselli, & Baker,2009; Lane, Thompson, Reske, Gable, & Barton-Arwood, 2006; Lang et al., 2009). Participants’ skin-picking had resulted indamage ranging from minor (e.g., superficial tissue damage to hands; Luiselli, 1989) to severe (e.g., prolapsed rectumrequiring multiple hospitalizations; Stokes & Luiselli, 2009).

2.2. Settings

All of the studies reviewed provided descriptions of the intervention setting. Intervention was implemented in residentialor institutional facilities (e.g., Blankenship & Lambarts, 1989; Luiselli, 1989), community or vocational settings (e.g., Stokes &Luiselli, 2009), classrooms (Lane et al., 2006), and therapy rooms within hospitals or clinics (e.g., Tiger, Fisher, & Bouxsein,2009). Slifer, Iwata, and Dorsey (1984), conducted intervention in an individual therapy room and also in a group therapyroom both within a clinical setting.

2.3. Functional assessment

Nine studies (56%) conducted some form of functional assessment in order to identify potential maintainingconsequences for skin-picking and to guide the development of intervention (Sigafoos, Arthur, & O’Reilly, 2003). Narrative

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descriptions of antecedents, behaviors, and consequences (ABC) were recorded in written form by researchers andresidential facility staff (e.g., Blankenship & Lambarts, 1989; Lane et al., 2006). In an ABC assessment, the assessor takes noteof changes in the participant’s environment immediately prior to the behavior and contingent upon the behavior.

Some form of functional assessment interview was conducted in four studies. Similar to direct observation methods,functional assessment interviews are designed to identify maintaining environmental contingencies by interviewingcaregivers. These interviews were conducted without a formal set of questions or scoring system in two studies (Lane et al.,2006; Lang et al., 2009) and using structured formal interview procedures in three studies (Ladd et al., 2009; Lang et al., 2009;Stokes & Luiselli, 2009). The structured interviews included the Motivational Assessment Scale (MAS; Durand & Crimmins,1988), the Questions About Behavioral Function Scale (QABF; Paclawskyj, Matson, Rush, Smalls, & Vollmer, 2001), and theFunctional Analysis Screening Tool (FAST; Iwata & DeLeon, 1996). Lang et al. (2009) conducted an informal functionalassessment interview with the participant and the QABF with the participant’s mother.

Four studies conducted analog functional analyses of skin-picking (Richman, Wacker, Asmus, & Casey, 1998; Slifer et al.,1984; Stokes & Luiselli, 2009; Tiger et al., 2009). This methodology involves exposing participants who engage in problembehavior to multiple test conditions in which potential reinforcing consequences (e.g., escape from demands or the deliveryof adult attention) are withheld and delivered only following problem behavior (Iwata, Dorsey, Slifer, Bauman, & Richman,1982/1994; Northup et al., 1991). The levels of problem behavior in each test condition are then compared to a controlcondition in which the same reinforcers are delivered independent of problem behavior. Test conditions that result inelevated levels of problem behavior relative to the control condition indicate that problem behavior is sensitive to thatparticular reinforcer and thus treatment decisions can be directed towards the identified behavioral function. Mostmethodologies for assessing function rely on observing behavior and noting the correlation between environmentalconditions and behavior (e.g., ABC assessments and functional interviews). However, the analog functional analysis movesbeyond correlation and is able to demonstrate a functional relation through systematic manipulations (Hanley, Iwata, &McCord, 2003).

Heidorn and Jensen (1984) stated that skin-picking for their participant functioned to obtain attention from caretakersand escape task demands. This determination was made from reviewing the participant’s medical records and by analyzingvideo tapes. However, the exact manner in which tapes were analyzed and the nature of the information drawn from medicalrecords was not provided. Therefore, a definitive statement regarding how function was determined in that study was notpossible.

Across the nine studies in which some method of functional assessment was used, eight reported that skin-picking wasmaintained, at least in part, by automatic reinforcement (e.g., sensory stimulation or contingent arousal reduction). Forexample, Slifer et al. (1984) hypothesized that participant’s eye gouging was maintained by automatic reinforcement in theform of visual stimulation (i.e., appearance of bright flashes when gouging eyes). Two studies reported skin-picking to bemaintained by socially mediated consequences. Stokes and Luiselli (2009) hypothesized that rectal skin-picking wasmaintained by escape from work and attention from staff as well as automatic reinforcement. Heidorn and Jensen (1984)reported skin-picking to be maintained by escape from work and obtaining attention from staff, but did not report thepotential for an automatic or self stimulatory function.

2.4. Intervention procedures

A variety of behavioral interventions were used to treat skin-picking. Four studies involved some form of protectiveclothing or equipment that physically prevented the participants from engaging in skin-picking (Blankenship & Lambarts,1989; Dorsey et al., 1982; Lang et al., 2009; Luiselli, 1989). This included the use of a helmet, face mask, cotton gloves, andcovering areas commonly picked with bandages (see Table 1). Protective equipment was either used contingently (placed onparticipant following skin-picking) or noncontingently (worn by participant at all times).

Differential reinforcement was used in 13 studies. Differential reinforcement of other behavior (DRO) was used in sevenstudies (see Table 1). In a DRO system, reinforcement is given following a period of time in which the target behavior (i.e.,skin-picking) is absent. Five studies used differential reinforcement of incompatible behavior (DRI). DRI involves reinforcinga target behavior that cannot physically occur at the same time as the problem behavior. For example, Heidorn and Jensen(1984) reinforced the participant for sitting on his hands. Differential reinforcement of alternative behavior (DRA) was usedin two studies. DRA involves reinforcing a specific behavior that is not necessarily incompatible with the target behavior.When this alternative behavior serves the same social function (e.g., obtaining attention or requesting a break from work) asthe problem behavior it is called Functional Communication Training (Carr & Durand, 1985).

Four studies provided participants with preferred items or competing activities as an antecedent approach. For example,Ladd et al. (2009), Lane et al. (2006), and Mulick, Hoyt, Rojahn, and Schroeder (1978) allowed participants to select preferredtoys from an array and then maintain access to these items or exchange them for new items. Participants in these studiesengaged in less skin-picking when they had access to toys.

Five studies used some form of punishment. Overcorrection in the form of contingent arm exercises was used in twostudies. Verbal reprimands and response interruption was (e.g., firmly stating or yelling ‘‘NO’’ contingent upon skin-picking)was used in four studies. Wesolowski and Zawlocki (1982) implemented an ‘‘auditory time out’’ for two females withprofound intellectual disability and blindness. Auditory time out involved placing headphones on the participants thatblocked almost all noise as a punishment for skin-picking. Dorsey, Iwata, Ong, and McSween (1980) sprayed a fine mist of

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water in the face of a 25-year-old female with profound intellectual disability contingent upon skin-picking. Otherintervention components included awareness training, limiting access to environments associated with skin-picking, self-management, matched stimulation, and extinction (see Table 1).

2.5. Outcomes

In terms of reducing skin-picking, outcomes across studies were judged to be positive. The mean PND across studies was97% (range, 75–100%). For Mulick et al. (1978), however, the PND could not be calculated due to a zero quantity in baseline.Across studies, improvement in skin-picking was measured by frequency count of skin-picking behavior, partial intervaldata collection, counting hospitalizations, and counting the number of open sores. Nine studies collected maintenance dataand demonstrated persistent treatment effects following intervention from 2 to 35 months.

2.6. Certainty of evidence

All studies identified for review utilized single-subject designs, specifically, some form of withdrawal or reversal design(e.g., ABAB), some form of multiple baseline design (e.g., multiple baseline across participants or settings), or an ABintervention-only design. The certainty of evidence for an intervention effect was rated as conclusive for all but three of thereviewed studies (Azrin et al., 1975; Conley & Wolery, 1980; Stokes & Luiselli, 2009). In all three cases the reason why theresults were judged to be inconclusive was because of the use of a pre-experimental A–B design.

3. Discussion

Our systematic search yielded 16 studies involving the treatment of skin-picking in individuals with developmentaldisabilities. Summaries of these studies revealed that the existing literature base is perhaps best described as limited.Currently, none of the reviewed treatments would qualify as ‘‘well established’’ according to criteria described by Odom et al.(2005). In terms of scope, the current database must be considered limited because of the sheer paucity of studies and thesmall number of participants (n = 19). Definitive statements regarding the effects of any individual intervention component(e.g., DRO, punishment, protective equipment) are further limited due to the research designs utilized in the reviewedstudies and the fact that most studies (n = 10) implemented multiple treatment components simultaneously. However, interms of the main aim of this review (i.e., to guide and inform practitioners in the assessment and treatment of skin-picking)the reviewed studies do provide preliminary evidence that behavioral treatments may be effective for skin-pickingtopographies.

Several of the reviewed studies implemented intervention components designed to be aversive (e.g., auditory time out forblind children) or restrictive (e.g., wearing helmets or straightjackets). Although these intervention components wereevaluated and found to be effective, there exists a clear trend over time within the reviewed studies towards the use of lessrestrictive procedures, antecedent interventions, and differential reinforcement. For example, all of the studies usingaversive procedures were published before 1982 and, although restrictive clothing and equipment has been incorporated inrecent treatment packages, its use has changed from continuous (i.e., restrictive equipment worn at all times) to contingent(i.e., worn briefly following skin-picking). A few well designed studies have directly compared continuous protective(restrictive) equipment to contingent protective equipment and found that contingent use may be more effective and/oreasier to fade from the intervention than continual use (e.g., Dorsey et al., 1982; Luiselli, 1989).

We found evidence in this review to support the use of antecedent- and reinforcement-based interventions. Severalstudies reported elimination or near elimination of skin-picking behavior using only antecedent manipulations. For example,several studies demonstrated that merely providing free access to preferred items and activities as an antecedentintervention was sufficient to reduce skin-picking (e.g., Ladd et al., 2009; Lane et al., 2006; Mulick et al., 1978). Furthermore,the single most common intervention component was differential reinforcement.

The most common hypothesis regarding skin-picking is that it is elicited by an elevated arousal level induced bycontextual events and in the absence of adaptive coping behavior. Specifically, persons who engage in skin-picking oftenreport high levels of tension, anxiety, or stress prior to or during skin-picking and a reduction in these emotions during andfollowing skin-picking (Deckersbach et al., 2002). In these cases, skin-picking likely serves a nonsocial function and may bemaintained by automatic reinforcement (i.e., the regulation or reduction of an aversive internal state) (Deckersbach et al.,2002; Didden et al., 2007). All of the reviewed studies that implemented some form of functional assessment reported thatskin-picking appeared to be maintained by automatic reinforcement, which would seem to provide some support for thisarousal reduction hypothesis.

In some cases functional assessments suggested the automatic reinforcement maintaining skin-picking may be in theform of sensory stimulation in addition to (or opposed to) arousal reduction. For example, Lang et al. (2009), hypothesizedthat the skin-picking of a 17-year-old woman with Asperger’s may have been in part maintained by tactile stimulation (e.g.,smoothing out irregularities around lesions, bug bites, or acne). This hypothesis is consistent with Arnold et al.’s (2001)assertion that some patients are obsessed about skin irregularities and then engage in skin-picking in response to thosethoughts. In a second example, Slifer et al. (1984), hypothesized that the skin-picking around and within the eye sockets of a6-year-old boy with profound intellectual disability and visual impairment may have been maintained by the appearance of

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bright light resulting from picking or gouging eyes. Treatment in this case involved matching this proposed stimulation byshining an actual bright light in the face of the child within a DRO and DRI treatment package.

In regards to our second aim, to identify gaps in the existing database so as to stimulate future research efforts, severalsuggestions for future research have arisen from this review. Most importantly, more intervention research involvingrigorous experimental designs and larger numbers of participants is warranted. Given the exceptionally high prevalence ofskin-picking for persons with Prader–Willi and Smith–Magenis syndromes, additional studies that include participants withthese diagnoses are warranted.

The participants in the reviewed studies engaged in a variety of skin-picking behaviors ranging from mild to severe (e.g.,requiring hospitalization). Interventions appropriate for mild cases of skin-picking might not be appropriate in more severecases. Practitioners looking to the literature to guide their selection of appropriate treatment might be assisted by studiesreporting the severity of skin-picking using a standardized format. Although the reviewed studies provided descriptions ofthe type and extent of skin-picking, none of the studies reported using a standardized assessment of severity. The Skin-Picking Impact Scale (SPIS; Keuthen, Wilhelm, et al., 2001; Keuthen, Deckersbach, et al., 2001) and The Milwaukee Inventoryfor the Dimensions of Adult Skin-picking (MIDAS; Walther, Flessner, Conelea, & Woods, 2008) both have reliability andvalidity data and may be appropriate with adults and those capable of accurate self-report. The Self-Injury Trauma Scale (SIT;Iwata, Pace, Kissel, Nau, & Farber, 1990) may be more appropriate with children and individuals with severe developmentaldisability.

It has been hypothesized that internal states (e.g., arousal) may set the occasion for skin-picking and that skin-pickingmay function to reduce or eliminate these states (see above). This theory seems to suggest two potential treatmentapproaches. First, when the presence of a co-morbid psychiatric condition (e.g., anxiety disorder) is identified perhaps itmight be more effective to focus treatment on that condition as opposed to solely targeting skin-picking. Thus,diagnostically, skin-picking might be a symptom of an underlying psychiatric condition that needs treatment. However,complications regarding the treatment and diagnosis of anxiety in populations of individuals with developmentaldisabilities may preclude the effectiveness of this approach for individuals with more severe disabilities. An alternativeapproach, also requiring future research, is to develop methods for identifying environmental stimuli likely to producearousal/anxiety and, using this information, then attempt to alter the individual’s environment to reduce the presence ofthese stimuli and/or to teach the individual skills which function to remove these stimuli.

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