identifying empirically supported treatments for phobic avoidance in individuals with intellectual...

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Behavior Therapy 39 (2008) 151–161www.elsevier.com/locate/bt

Identifying Empirically Supported Treatments for PhobicAvoidance in Individuals With Intellectual Disabilities

Heather K. Jennett, Louis P. HagopianKennedy Krieger Institute and Johns Hopkins School of Medicine

This paper reviews the literature regarding the treatment ofphobic avoidance in individuals with intellectual disabilities.Criteria for classifying interventions as empirically supported,developed by the American Psychological Association (APA)Division 12 Task Force on Promotion and Dissemination ofPsychological Procedures, were used. For studies employingsingle case experimental designs, criteria developed by APADivision 16 (Kratochwill & Stoiber, 2002; Shernoff, Kratoch-will, & Stoiber, 2002) were used to supplement Division 12criteria. Results indicate that behavioral treatment can bedesignated as a well-established treatment for phobic avoid-ance in individuals with intellectual disabilities.

THERE IS SOME EVIDENCE to suggest that indivi-duals with intellectual disabilities may be at in-creased risk for several types of psychiatric dis-orders, including anxiety disorders. For example,Dekker and Koot (2003) found that approximately22% of a Dutch community sample of 474individuals (age 7 to 20 years) with intellectualdisabilities met Diagnostic and Statistical Manualof Mental Disorders (DSM-IV-TR; American Psy-chiatric Association, 2000) criteria for some formof anxiety disorder, with 17.5% of this samplemeeting the diagnostic criteria for a specific phobia.Another study found that 13.6% of a Canadiansample of children with autism and Asperger'ssyndrome were found to experience “generalized

Address correspondence to Heather K. Jennett, Ph.D., Depart-ment of Behavioral Psychology, Kennedy Krieger Institute, 707 N.Broadway, Baltimore, MD 21205; e-mail: [email protected]/08/151–161$1.00/0© 2008 Association for Behavioral and Cognitive Therapies. Published byElsevier Ltd. All rights reserved.

anxiety” (Kim et al., 2000). As a point ofcomparison, the 1-year prevalence of an anxietydisorder in the general population was found to be18.1%, whereas the 1-year prevalence of a specificphobia was found to be 8.7% (Kessler et al., 2005).These statistics suggest that individuals withintellectual disabilities experience anxiety at leastas much as the general population, if not more.Unfortunately, there is relatively little research on

the treatment of anxiety in intellectual disabilities.Of the studies that describe interventions targetinganxiety in individuals with intellectual disabilities,most do not apply DSM or other formal diagnosticcriteria to document the presence of an anxietydisorder. Therefore, in the current review, we willuse the term “phobic avoidance” to refer to clinicalproblems involving the avoidance of particularsituations or stimuli that were characterized byauthors as associated with anxiety or fear. We choseto use the term phobic avoidance instead of termssuch as “fear” or “anxiety” based, in part, on howthe target problem was assessed. Except for onestudy which used a self-report measure of fear, all ofthe studies reviewed exclusively obtained measuresof overt behavior (avoidance/approach). Therefore,due to the behavioral nature of the assessment, wefelt that a behavioral term was most appropriate fordescribing the phenomena involved in these cases.Nevertheless, we thought using the term “phobic”avoidance was important to clarify that avoidancewas coupled with responses universally consideredas indicators of anxious and fearful states (e.g.,crying, screaming, physical resistance, runningaway, shaking, wide eyes, grimacing, and aggres-sive or other problem behavior). Studies included inthe current review describe phobic avoidance of thetype and magnitude characteristic of specificphobia or other anxiety disorders for which aspecific stimulus/situation is avoided or

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152 j ennett & hagop i an

encountered with great distress. In light of thisissue, comparisons between studies on the treat-ment of formally diagnosed specific phobias intypically developing individuals should be madewith some caution. Nevertheless, there are enoughsimilarities to make this a reasonable point ofreference.Chambless and her colleagues (1998) employed

APA Division 12 criteria for empirically supportedtreatments for a range of disorders in adults, in-cluding specific phobias. Exposure was classified as“well-established” and systematic desensitizationas “probably efficacious” for the treatment ofspecific phobias in adults. For children andadolescents diagnosed with specific phobias, Ollen-dick and King (1998) identified reinforced practiceand participant modeling as well-established treat-ments. Additionally, systematic desensitization,modeling (in vivo and filmed), and cognitivebehavior therapy met the criteria for “probablyefficacious” treatments for specific phobias basedon existing studies.In a more recent review of the literature on the

treatment of specific phobias in children, Davis andOllendick (2005) proposed a more comprehensivemethod for defining treatment efficacy of interven-tions targeting anxiety that extends the originalDivision 12 criteria. The approach described isbased on bioinformational theory, which assertsthat behavior, physiology, and verbal responses/cognition are separate response components thatcollectively comprise the emotional response (in thecase of specific phobia, the phobic response alsoincludes “subjective fear”). The authors make areasoned case that interventions for specific pho-bias can be most effective when designed to targeteach of these response components but acknowl-edge that this model requires empirical substantia-tion. Using this conceptual framework, Davis andOllendick evaluated the efficacy of interventions forspecific phobia with consideration of the extent towhich outcomes included measures of each of theemotional response components relevant to anxiety(behavior, physiology, verbal responses/cognition,and subjective fear). Studies were also evaluatedwith regard to correspondence between the specificresponse components each intervention presumedto target and the response components used as theoutcome measures.Their review of the literature revealed that most

studies failed to include measures of all the responsecomponents and that there was little correspon-dence between putative response component targetsand outcome measures. Nearly all studies used abehavioral outcome measure, and most included ameasure of subjective fear. However, very few in-

cluded measures of physiology or cognition.Reinforced practice and participant modelingwere the interventions for which there was thehighest level of correspondence between the re-sponse component targets and outcome measures.These interventions, along with one-session treat-ment (Öst, 1997), were classified as “well-estab-lished” for addressing the behavior responsecomponent, as “probably efficacious” for thecognitive response component, and “experimental”for the physiology component.The purpose of the current review was to critically

examine the existing literature on the efficacy oftreatments for phobic avoidance in persons withintellectual disabilities. Specifically, criteria describedby Divisions 12 (Clinical) and 16 (School) of theAmerican Psychological Association (APA) for eval-uating the empirical support for interventions(Kratochwill and Stoiber, 2002; Task Force, 1995)were used to examine the literature on the treatmentof phobic avoidance in individuals with intellectualdisabilities. Studies also were evaluated using theframework proposedbyDavis andOllendick (2005).

Methodarticle selection

Articles were initially located by reviewing pub-lished studies listed in the PsycINFO and PubMeddatabases between 1970 and February 2007. Twosearch terms, one from each category, were alwayscombined and each term was combined with everyother term in the other category. The terms were asfollows: (a) mental retardation, intellectual disabil-ity, developmental disability, developmental disor-der, autism, or autistic disorder; and (b) avoidantbehavior, avoidance, anxiety, anxiety disorder,anxious, phobia, phobic, or fear. Following thisinitial step, the abstracts of the articles meeting theabove criteria were reviewed to determine if theauthors had implemented a psychological treatmentfor the avoidance or fear of a specific stimuluscharacteristic of specific phobia. All articles usingmedication as treatment or focused solely on theassessment or diagnosis of anxiety in individualswith developmental disabilities were excluded. Thereferences of the remaining articles were thenreviewed to ensure that no relevant articles hadbeenmissed in the PsycINFO and PubMed searches.In the final step, the abstracts of all initially includedarticles were reviewed and studies were eitherincluded or excluded in the current review basedon the criteria described above. Included articleswere subsequently coded to determine the efficacyof interventions for phobic avoidance in individualswith intellectual disabilities.

153phob ic avo idance in the inte ll ectually d i sabled

article review and coding

This search yielded 38 articles: 4 were group studies,13 were single-case designs, and 21 were nonexper-imental designs (e.g., AB designs) or uncontrolledcase reports. The group studies and single-casedesigns were retained and reviewed in more detailby the first author (H.K.J). All the articles werecoded in accordance with Division 12 and 16criteria (see below) with regard to the specificationof participant characteristics, study characteristics(number of participants, use of treatment manual,etc.), and analysis of experimental control. Reliabil-ity of coding was evaluated by having a secondperson independently code all the group studies and38% of the single-case studies. To more easilydetermine agreement between readers, a codingsystem, adapted from the Division 16 codingmanual (see below), was developed for the single-case studies such that numeric codes were assignedto qualitative variables (e.g., stability of baselinephase, change in behavior with treatment) andquantitative variables (e.g., number of participants)were entered as is. All data were entered into aMicrosoft Excel database.

interobserver agreement

A second independent reader coded 100% of thegroup studies and 38% (5 of 13) of the single-casestudies. Interobserver agreement was calculatedusing the exact agreement formula [number ofagreements/(number of agreements+number ofdisagreements)]*100. For group design studies, anagreement was defined as both observers recordingthe same response (e.g., yes/no) for each character-istic of the Division 12 Task Force criteria. Forsingle-case studies, an agreement was defined asboth coders assigning the same numeric code, and adisagreement was defined as each coder assigning adifferent numeric code. The average reliabilitycoefficient was 100% for group studies and 91%(range: 83% to 97%) for single-case studies.

criteria for determining empiricallysupported treatments

Division 12 (Task Force, 1995) classifies empiricallysupported treatments as “well-established,” “prob-ably efficacious,” and “experimental” treatments.For treatments to be classified as well-establishedthere must be at least two good between-groupdesigns or more than nine single-case studies thathave been found to be statistically significantlysuperior to another treatment, pill, or placebo, orequivalent to an already established treatment. Ex-periments must be conducted using treatmentmanuals or contain clear descriptions of the treat-ment procedures; characteristics of the sample must

be specified; and the effects must be replicated byindependent research groups such that at least twodifferent research teams have found the treatment tobe efficacious. Treatments may be classified asprobably efficacious if: (a) at least two experimentsusing group designs show that the treatment is statis-tically significantly superior to a wait-list controlgroup; or (b) at least one group design experimentmeets the well-established criteria; or (c) at least threewell-controlled single-case design experiments meetthe well-established criteria. Treatments that do notmeet the criteria for either of these categories areconsidered experimental.Division 12's requirements for empirically sup-

ported treatments include criteria for single-case aswell as group designs. Although the criteria forgroup designs are based on well-establishedprinciples of experimentation, the criteria forsingle-case designs lack sufficient detail to permitreliable classification of these studies with regardto determination of treatment efficacy and exper-imental control. Division 16 also has describedcriteria for identifying evidence-based interven-tions in schools (Kratochwill and Stoiber, 2002).Whereas the Division 12 criteria are most appro-priate for evaluating research on the treatment ofclinical disorders employing group designs, theDivision 16 criteria are designed to evaluate abroader range of prevention and interventionprograms for school-based problems and providespecific criteria appropriate for both group andsingle-case designs.Given that the current review focuses on the

treatment of a significant clinical problem, most ofthe articles employed single-case designs, and mostinvolve direct observation of behavior, neither of theclassification schemes was completely applicable. Inthe current study, we categorize interventions intothe Division 12 categories of well-established,probably efficacious, and experimental treatments.We apply the Division 12 criteria for evaluating thestudies using group designs; however, for studiesemploying single-case designs, we supplement theDivision 12 criteria with criteria derived from thecoding procedures of Division 16. Furthermore, weadapt some of the Division 16 criteria based on thenature of the problem of phobic avoidance andexclude a small number of the criteria that we feltwere not applicable to evaluating treatment studiesfor a clinical problem. On the whole, we believethese adaptations to be consonant with the princi-ples underlying the criteria developed by bothDivisions 12 and 16—and based onwell-establishedand accepted principles and procedures for the useof single-case designs (e.g., Barlow and Hersen,1984; Kazdin, 1982; Morgan and Morgan, 2001).


However, we do not advocate broader applicationof these adaptations in the absence of additionaldiscussion.

adaptations of division 16 criteriafor coding single-case designs

As noted, Division 16 criteria provide moreguidance with regard to determining the quality ofexperimentation and determination of experimen-tal control for single-case studies. Thus, criteria forjudging the quality of baseline, appropriate use ofmeasurement, and evaluation of treatment outcomethrough visual analysis were applied. Criteria forevaluating the quality of baseline consisted ofexamining the length of the baseline (which shouldbe at least three data points), the stability of thedata, whether there is an overlap of data with thetreatment phases, if the level of behavior was severeenough to warrant intervention, and if the trends inthe data were stable or in the opposite direction of adesired treatment effect. Studies were also evaluatedfor appropriate use of measurement, such as thecollection of interobserver agreement data andwhether the measures used reflected the goals ofthe intervention. Treatment outcomes were assessedthrough visual analysis of graphically depicted datawith consideration of the following factors: changein the level of behavior relative to baseline, changein the trend of the data to the desired direction, thelength of the treatment phase (which should be atleast three data points), the stability of data, andminimal overlap in the level of behavior betweenthe baseline phase and the treatment phase.With regard to the determination of treatment

efficacy, theDivision 16manual provides criteria forclinical (or educational) significance. It is broadlydefined as a change in the diagnostic criteria, out-comes assessed through continuous variables (e.g., asignificant percentage of participants who fall in the“normal range”), and through social validation ofthe intervention. In the case of treatment for phobicavoidance, approach responses (though they mayvary in their form across participants) represent auniformly applicable and objective index of treat-ment efficacy that would fall in the category of an“outcome assessed through a continuous variable.”Although this outcome measure represents only oneof the response components (i.e., behavior) de-scribed by Davis and Ollendick (2005), it was notpossible to evaluate outcomes with respect to otherresponse components because those were notmeasured in most studies. For the purposes of thecurrent review, we adapted the Division 16 criteriarelated to outcomes of “educational/clinical signif-icance” by objectively defining treatment efficacy asthe participant displaying at least 90% of the

targeted approach response (i.e., the participantsuccessfully completes 9 out of 10 steps in ahierarchy or remains in proximity to the fearedstimulus for 90%of the time targeted for treatment).In the case of multiple participants, at least two-thirds of participants had to meet this criterion. Assuggested by Davis and Ollendick (2005), we alsoexamined the extent to which each study obtainedmeasures within each of the emotional responsecomponents (physiology, verbal response/cognition,behavior, and subjective fear) and the extent towhich outcome measures corresponded to putativeresponse component targets.

Resultssingle-case experiments

Each study was coded for experimental control aswell as whether the participants attained thetreatment goal (based on the criteria describedabove). Twelve of 13 studies using single-casedesigns demonstrated treatment efficacy throughthe use of good experimental design (see Table 1). Itshould be noted that, although all of the studiescompared the treatment to a baseline condition, onestudy (Conyers et al., 2004) also compared twotreatments (for 2 of 6 participants) after the firsttreatment did not prove to be efficacious. These 12articles were published between 1981 and 2006.

Participant characteristics. Participant character-istics in the 12 studieswere coded for the variables ofage, primary diagnosis, level of mental retardation,and gender (see Table 2). Half of the participants inthese studies were adults, whereas the other halfwere younger than 21 years of age. The majoritywere male (68%) and had a primary diagnosis ofmental retardation (71%). All participants, includ-ing those with autism as a primary diagnosis (29%),had some cognitive impairment, ranging from mildto profound, with the largest proportion of partici-pants falling into the severe range (39%).

Study characteristics. The included studies werealso coded for number of participants, type ofsingle-case design, whether interobserver agreementor treatment integrity data were collected, and thesetting and therapist for the treatment beinginvestigated (see Table 3). The average number ofparticipants per study was 2.3 (range: 1 to 6). Themost frequently used single-case design was a mul-tiple baseline design across participants or settings(67%). All multiple baseline designs were includedif the majority of participants benefited from thetreatment. This included a minimum of 2 partici-pants or settings. Two studies used mixed designs,indicated separately in Table 3. The treatments tookplace in a variety of settings and were administered

Table 1Empirically supported treatment criteria and the status of studies employing single-case designs to evaluate the treatment of phobicavoidance in individuals with intellectual disabilities

Demonstration of experimental control Determinationof efficacy

Treatment manual Clientcharacteristics

Good experimentaldesign

Treatment superiorto baseline w/replications

Attainmentof 90% oftreatment goal

Description oftreatment equivalentto treatment manual

Clearlyspecified

Burgio et al. (1986) Yes Yes Yes Yes YesConyers et al. (2004) Yes Yes Yes Yes YesEfranian and Miltenberger (1990) Yes Yes Yes Yes YesHagopian et al. (2001) Yes Yes Yes Yes YesLove et al. (1990) Yes Yes Yes Yes YesLuscre and Center (1996) Yes Yes Yes Yes YesMaguire et al. (1996) Yes Yes Yes Yes YesMatson (1981a,b) Yes Yes Yes Yes YesRapp et al. (2005) Yes Yes Yes Yes YesRiccardi et al. (2006) Yes Yes Yes Yes YesRunyan et al. (1985) Yes Yes Yes Yes YesShabani and Fisher (2006) Yes Yes Yes Yes YesWaranch et al. (1981) No Yes Yes No Yes


by a variety of therapists, with the highest percent-age being conducted in community settings (42%)and implemented by advanced degree professionals(42%); those that were implemented by therapistswithout an advanced degree were superviseddirectly by advanced degree professionals. All butone of the studies (92%) assessed interobserveragreement on the dependent variables, and only onestudy collected procedural reliability data ontreatment implementation. None of these studiesused a treatment manual but all described proce-dures with sufficient detail to permit replication.

Phobic stimuli and avoidant behaviors. In thestudies meeting criteria, the phobic or avoidedstimuli included water (Love et al., 1990; Rapp

Table 2Participant characteristics in single-case studies meeting criteria

Category Percentage (numberof participants)

AgeChildren (age b12) 32% (9)Adolescents (age 12 – 21) 18% (5)Adults (age N21) 50% (14)

Primary diagnosisMental retardation 71% (20)Autism 29% (8)

Level of mental retardationMild 7% (2)Moderate 21% (6)Severe 39% (11)Profound 21% (6)Unspecified 11% (3)

GenderMale 68% (19)Female 32% (9)

Total 100% (28)

et al., 2005), dogs (Efranian and Miltenberger,1990), strangers (Matson, 1981a), animatronicobjects (Riccardi et al., 2006), medical procedures(Hagopian et al., 2001; Shabani and Fisher, 2006),dental procedures (Conyers et al., 2004; Luscre andCenter, 1996; Maguire et al., 1996), going outside(Love et al., 1990), riding escalators (Runyan et al.,1985), and climbing stairs (Burgio et al., 1986). Ineach study, target behaviors were referred to usingat least one the following terms: avoidance, fear,phobia, or anxiety. Every article provided an ob-servable operational definition of avoidant beha-viors for each individual participant. In general,avoidant behaviors included a cluster of responsesfrom among the following: crying, screaming,

Table 3Characteristics of single-case studies meeting criteria

Category Percentage (number of studies)

Type of designMultiple baseline 67% (8)Changing criterion 25% (3)Reversal 25% (3)

Interobserver agreement 92% (11)Procedural reliability 8% (1)SettingCommunity 42% (5)School 17% (2)Home 17% (2)Inpatient 25% (3)Outpatient 17% (2)

TherapistStudy Author 42% (5)Parent 17% (2)Teacher 8% (1)Other/not reported 33% (4)

Total 100% (12)


physical resistance, running away, shaking, wideeyes, grimacing, aggressive behavior, disruptivebehavior, self-injurious behavior, and refusal toapproach feared stimulus or related stimuli. In mostcases, anxiety was assessed through direct observa-tion of behavior, facilitated by a BehavioralAvoidance Test (BAT; e.g., Efranian and Miltenber-ger, 1990) or through caregiver report, or based ona referral interview or measures such as theLouisville Fear Survey (Miller et al., 1972, as citedin Matson, 1981a). Only two cases referred to theDSM criteria for specific phobias (Hagopian et al.,2001: the participant was diagnosed with blood-injury-injection phobia; Riccardi et al., 2006: theparticipant met criteria for specific phobia).

Dependent variables. Across studies, the reduc-tion of phobic avoidance was measured by differentdependent variables; however, all of the studies useddirect observation of behavior to collect data on theprimary dependent variable. Similar to the resultsreported by Davis and Ollendick (2005) in theirreview of interventions for specific phobias inchildren, we found that all studies measured thebehavior response component (and none includedmeasures of physiology or verbal responses/cogni-tion). Only two studies (Love et al., 1990; Matson,1981a) obtained measures of subjective fear usingrating or Likert-type scales, such as self-ratings orothers' ratings of fear experienced by the participant.The main dependent variables included number ofapproach steps taken (Love et al., 1990), number oftask analysis/hierarchy steps completed (Conyerset al., 2004; Hagopian et al., 2001; Luscre andCenter, 1996; Runyan et al., 1985), distance fromthe feared stimulus (Efranian and Miltenberger,1990; Matson, 1981a), level of resistance (Maguireet al., 1996), percent compliance (Burgio et al.,1986; Shabani and Fisher, 2006), percentage ofintervals at criterion level (Riccardi et al., 2006), andrate of problem behavior (Rapp et al., 2005).

Treatment components. The components com-prising each treatment package implemented in thestudies reviewed were described separately. Thiswas necessary because the terms used by authorsto describe the treatment components or treatmentpackages varied from article to article. In somecases, the components comprising each packagealso differed slightly despite being labeled thesame. Therefore, a definition of each componentwas created and each treatment package wasreviewed to determine what components itcontained. Seven main treatment componentswere identified:

1. In vivo exposure: The participant was ex-posed to the actual feared stimuli or situation.

2. Hierarchy: The task of engaging with orapproaching the feared stimulus was brokendown into small steps, with gradualincreases in requirements. Steps were brokendown either chronologically (i.e., task anal-ysis) or based on a dimension, such as timeexposed to stimulus, size of stimulus, ordistance to stimulus (i.e., stimulus fading).An increase in the requirement was usuallydependent on the participant's performanceat the previous step. In behavioral literature,this may also be referred to as shaping orstimulus fading.

3. Contingent Reinforcement: Contingent socialpraise or a tangible reward (e.g., money, to-kens) was given when the participant engagedin approach behavior (toward the fearedstimulus) or complied with a feared taskwithout refusal behaviors (e.g., cooperatedwith a dental procedure without resisting).

4. Prompting: Verbal prompting or physicalguidance was used to assist the participantto engage appropriately with the feared stim-ulus. The prompts may or may not have beenfaded throughout treatment.

5. Modeling: Another individual engaged withthe feared stimulus appropriately (either liveor on video) while the participant observed.This may include the model moving throughsteps of a hierarchy and/or receiving rein-forcement for appropriate behavior.

6. Extinction/Blocking: The participant was notpermitted to escape or stop the current stepdue to avoidance or problem behaviors. Thiswas typically done through physically guidingthe participant to engage in a step or blockingthe participant from escaping.

7. Use of Distracting Stimuli: The participanthad noncontingent access to stimuli to en-courage appropriate or incompatible behavior(e.g., to help the participant relax or provide adistraction). This stimulus was typicallysomething rewarding to the participant andaccess may have been given before or duringexposure to the feared stimulus.

As shown in Table 4, every treatment packageincluded in vivo exposure to the avoided stimulusand reinforcement for appropriate behavior (e.g.,approach). Eight of 12 studies (67%) also used ahierarchy for structuring graduated exposure to thefeared stimulus. Other components used in sometreatment packages include modeling (58%),prompting (67%), use of distracting stimuli (33%),and escape extinction or blocking (17%). Somestudies (33%) also used additional components, such

Table 4Treatment components in single-case studies meeting criteria

Article Authors' name Treatment componentsfor procedure In vivo

exposureReinforcement Prompting Modeling Hierarchy Distraction Extinction

Burgio et al. (1986) Operant basedprocedures

X X X X

Conyers et al.(2004)

In-vivo desensitization X X X X

Efranian andMiltenberger(1990)

Contact desensitization X X X X X X

Hagopian et al.(2001)

Multicomponent operantbased procedures

X X X X X

Love et al. (1990) Participant modeling withreinforcement

X X X X X

Luscre and Center(1996)

Systematicdesensitization

X X X X X X

Maguire et al.(1996)

Behavioral intervention X X X

Matson (1981a,b) Participant modeling X X X X XRapp et al. (2005) Operant based

proceduresX X X X

Riccardi et al.(2006)

Contact desensitization X X X

Runyan et al.(1985)

Contact desensitization X X X X X

Shabani andFisher(2006)

Operant basedprocedures

X X X


as extra practice between sessions, frequent breaks,manipulation of medical equipment prior to expos-ing the participant to using it in a real situation, andoccasional use of anti-anxiety medication (e.g.,alprazolam).Although a number of different treatment com-

ponents were employed in these studies and dif-ferent authors referred to their treatment packageusing various names, we chose to characterize treat-ment packages containing these components withinthe broader class of behavioral treatment. Specifi-cally, these interventions are: (a) based on learningprinciples; (b) focused on directly exposing theindividual to the feared stimulus while reinforcingapproach responses; (c) routinely used in combi-nation with other behavioral treatment componentsincluding prompting and hierarchies; and (d) donot involve procedures aimed at targeting any-thing other than overt behaviors—such as cogni-tions, underlying conflicts or issues, or physiologicalstates.

group designsIn addition to the single-case studies describedabove, four group studies were identified, but nonemet the criteria for empirically supported treat-ments (see Table 5). Only one included a placebocontrol condition with random assignment toexperimental groups (Peck, 1977). The Peck

study compared three types of desensitizationprocedures (contact desensitization, vicarious sym-bolic desensitization, and systematic desensitiza-tion) with a placebo-attention control conditionand a no-treatment control condition for treating afear of rats or heights in adults with mildintellectual disabilities. All three desensitizationprocedures involved gradually exposing the parti-cipants to the feared stimulus, but the mode ofpresentation differed (e.g., in vivo, videotaped, andimagined). However, there were no statisticallysignificant differences between the groups withregard to pulse rate, self-ratings of fear, observedfear, or approach toward the feared stimulus aftertreatment; although there were trends towardsignificance for the contact desensitization group.In addition, this study had a relatively small samplesize (n=20) for the particular design used, whichlimits its power.An additional study (Altabet, 2002) used a wait-

list control group as the comparison for the exper-imental group in treating the avoidance of dentalprocedures in individuals with severe to profoundintellectual disabilities. However, neither randomassignment to groups nor participant matching wasused. The groups were not equivalent prior totreatment as the treatment group exhibited greaterresistance to the dental procedures prior to treat-ment than did the control group. Treatment

Table 5Empirically supported treatment criteria and the status of group studies evaluating the treatment of phobic avoidance in individuals withintellectual disabilities

Superior to pill,placebo, or othertreatments

Equivalent toestablishedtreatment

Superior towaitlist control

Treatment manual orequivalent description

Clientcharacteristicsspecified

Altabet (2002) No No Yes Yes NoMatson (1981a,b) No No No Yes YesObler and Terwilliger (1970) No No No Yes YesPeck (1977) No No No Yes Yes


consisted of gradual exposure to dental proceduresusing a hierarchy, modeling, shaping, paired relax-ation, and reinforcement. Following treatment, theexperimental group successfully achieved signifi-cantly more hierarchy steps than the control group,but therewas little difference in the need for restraintor sedation between the groups.The other two group studies (Matson, 1981b;

Obler and Terwilliger, 1970) found significantdifferences after behavioral treatment was imple-mented with their experimental groups, but only ascompared to no-treatment control groups. Specif-ically, Obler and Terwilliger (1970) implementedreinforced practice (termed modified systematicdesensitization by the authors), which consisted ofin vivo exposure and reinforcement. Matson(1981b) implemented participant modeling, whichconsisted initially of rehearsal and observation ofpeers engaging in the feared behaviors, followed bygraduated exposure with prompting as well astraining on coping skills. Although none of thesefour group studies used a treatment manual, theprocedures were described with sufficient detail topermit replication.

DiscussionAlthough there is an extensive body of research onthe treatment of anxiety in typically developingindividuals, a relatively small number of studieshave been published describing the treatment ofphobic avoidance in individuals with intellectualdisabilities. Based on our adaptation of criteriadescribed by Divisions 12 and 16 for determiningwhether an intervention can be characterized as anempirically supported treatment, we concluded thatthere is sufficient empirical support to characterizebehavioral treatment as a well-established treat-ment for phobic avoidance displayed by individualswith intellectual disabilities. In contrast to theresults of this review, the literature on the treatmentof specific phobias in typically developing childrenand adults describes other classes of interventions inaddition to behavioral treatment (e.g., cognitivebehavioral therapy [CBT], systematic desensitiza-

tion). Although CBT and systematic desensitizationboth target behavioral response components, theyalso target cognitive and physiological responsecomponents, respectively. Of the two studies wefound that described CBT in individuals withintellectual disabilities, neither was sufficientlycontrolled to meet Division 12 Task Force criteria.Thus, there is insufficient information to concludewhether other treatments for phobias designated asprobably efficacious (i.e., systematic desensitiza-tion, CBT) for typically developing children andadults may be effective for the treatment of phobicavoidance in individuals with intellectual disabil-ities. Therefore, CBT and systematic desensitizationmust be deemed as experimental for this populationbased on the current literature.All of the studies described that had good exper-

imental designs and were shown to be efficaciousincluded some form of live exposure to the fearedstimulus plus reinforcement for appropriate beha-viors (e.g., approach or absence of avoidance),suggesting that these are important components oftreatment. Thus, these findings are generally con-sistent with results of previous reviews whichindicated that reinforced practice and exposuremeet criteria as well-established treatments forspecific phobia in typically developing children(Davis and Ollendick, 2005; Ollendick and King,1998) and adults (Chambless et al., 1998), respec-tively. Although live exposure to the feared stimulusand reinforcement for appropriate behavior werecomponents of each treatment package, severalother behavioral treatment components commonlyused in concert with exposure and reinforcementalso were used. For example, some studies also useda hierarchy to structure the progression of exposurefrom lesser to more feared stimuli. Prompting wasused in some studies to occasion approach responsestargeted for reinforcement. Extinction of escape oravoidance was used in some studies, as were dis-traction and modeling.As indicated in Table 4, the terminology used to

describe interventions was not consistent acrossstudies reviewed (or relative to research in thebroader anxiety literature). For example, some


studies described their interventions as systematicdesensitization (e.g., Luscre and Center, 1996);however, careful inspection of their proceduressuggest this term may not have been entirelyappropriate. Rather than using relaxation to inducereciprocal inhibition, it appears that alternativestimuli were used simply to distract participantsduring exposure. Further, it appears that modelingwas conducted in different ways and for differentpurposes across studies. In some studies, it appearsthat modeling was used simply for instruction(perhaps to compensate for verbal deficits amongparticipants with intellectual disabilities). In threeof these studies, the intended purpose of modelingappeared to be for the more traditional purpose ofsocial learning (e.g., Love et al., 1991; Matson,1981a,b). Although these interventions did involveparticipant modeling as defined in previous reviewarticles, it appears that modeling was employed as aprocedure designed to facilitate exposure andincrease contact with reinforcement.Exposure and reinforcement were components

common to all the studies reviewed and couldarguably be characterized as the primary treatmentcomponents. Although additional research aimed atexamining the relative contribution of the varioustreatment components is needed, these findings aregenerally consistent with the findings of similarstudies indicating that exposure and reinforcementare key components in the treatment of anxiety.Consequently, we believe there is sufficient evidenceto support including exposure and reinforcement ascomponents in any intervention for phobic avoid-ance in individuals with intellectual disabilities.Other components should be included based onindividual client and parent/caregiver factors, suchas the individual's ability to learn via verbal instruc-tions versus modeling, to tolerate mild anxiety thatmay occur during exposure, and to respond to im-mediate versus delayed reinforcement.Within the framework provided by Davis and

Ollendick (2005), behavioral treatment can bemore specifically designated as well-established fortreating only the behavioral component of phobicavoidance in individuals with intellectual disabil-ities. None of the studies reviewed in this paperincluded measures of the cognitive and physiolog-ical components of the phobic response—which issimilar to what Davis and Ollendick reported intheir review of the research on the treatment ofspecific phobias in typically developing children.However, in contrast to their findings thatreinforced practice is also well-established fortreating subjective fear in children without intel-lectual disabilities, only two single-case studiesidentified in the current review included measures

of subjective fear and therefore it can only beclassified as experimental.Davis and Ollendick (2005) argue that interven-

tions that target only one component of the fearresponse associated with specific phobia may notproduce maximally effective outcomes. They sug-gest that eliminating the behavioral avoidancecomponent does not necessarily treat the fullemotional network associated with specific phobia.That is, although a participant may be able toapproach the feared stimulus with treatment, thefear may still be present until the cognitive andphysiological components of the response aretargeted as well. Espousing an entirely differenttheoretical framework, Friman, Hayes, and Wilson(1998) also argued that behavioral interventions foranxiety displayed by “language-able persons”should address not only overt behaviors but alsoprivate verbal events (cognitions, subjective fear)associated with behavioral avoidance. AlthoughDavis and Ollendick's conceptualization of anxietyas a multifaceted response warranting interventionsthat address each response component is elegant,logical, and, most importantly, testable, this modelawaits empirical validation. Moreover, a number ofpractical issues need to be resolved with respect tothe application of this model to individuals withsevere intellectual disabilities. That is, for personswho have severe communication deficits or who areuncooperative with measurement of physiologicalresponses, assessment of cognitions, subjective fear,and physiological responses may be not be feasible.Although a number of questions remain, the

results of our review suggest that phobic avoidancedisplayed by individuals with intellectual disabilitiesis amenable to treatment. One limitation of thisreview, however, is that the description of clinicalproblems we have collectively termed “phobicavoidance” differed between studies. As describedat the outset, we use the term “phobic avoidance” torefer to clinical problems involving the avoidance ofparticular situations or stimuli that were character-ized by authors as associated with anxiety or fear.The variation in the descriptions of clinical targetsand limited use of DSM diagnoses in this literaturelikely stems from the difficulty in assessing anddifferentially diagnosing anxiety disorders withinthis population. There are few instruments forassessing anxiety in this population, particularlyfor individuals with limited verbal skills, and littleresearch has been conducted to determine whetherthe common instruments for typically developingpopulations are valid for assessing anxiety withinthis population. In order for treatment outcomeresearch to specify the population or specificproblem for which the treatment is efficacious,


Chambless and Hollon (1998) suggest that samplesbe described in terms of a diagnostic system usingstandardized measures. Because of the difficulty indiagnosing anxiety in individuals with intellectualdisabilities, best practice states that direct observa-tion, along with a complete history, interviews, andrating forms, should be used (American Academy ofChild and Adolescent Psychiatry, 1999). Althoughthe majority of the studies reviewed did not usestandardized measures or make a diagnosis ofspecific phobia or another anxiety disorder accord-ing to DSM criteria, they each used direct observa-tion to continually assess the behaviors (avoidantbehavior) in order to establish a baseline and trackthe progress of the treatment. Although most of theparticipants in the studies reviewed displayedphobic avoidance to the extent that suggested thepresence of a diagnosis of specific phobia, adefinitive retrospective diagnosis is not possible.In addition, the studies reviewed described the

treatment of individuals with a wide range ofintellectual disabilities, varying from profound tomildmental retardation, andwith different etiologicalor associated conditions. Participants in the 12 studiesmeeting the criterion of demonstrating treatmentefficacy through the use of good experimental designranged in age from 4 to 54 years. The small samplesize and uniformly positive outcome precludes anyformal analysis of the effects of subject characteristicson treatment effects. However, future research shouldbe conducted to examine how treatment interactswith individual characteristics in this population.In conclusion, our review of the literature

revealed behavioral treatment involving exposureand reinforcement to be a well-established treat-ment for the behavioral component of phobicavoidance in individuals with intellectual disabil-ities. This information provides clinicians withempirical evidence to guide them in their approachto treatment; however, comparative studies shouldbe conducted to determine whether interventionsthat target the other components of the phobicresponse, including physiological and cognitive,more effectively treat phobic avoidance in thispopulation (Davis and Ollendick, 2005).

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