DEVELOPMENTAL MEDICINE & CHILD NEUROLOGY
SYSTEMATIC REVIEW
Behavioural intervention practices for stereotypic and repetitive behaviour in individuals with autism spectrum disorder: a systematic review STEPHANIE Y PATTERSON | VERONICA SMITH | MICHAELA JELEN Department of Educational Psychology, Faculty of Education, University of Alberta, Edmonton, Alberta, Canada. Correspondence to Stephanie Y Patterson at 6–123f Education North, University of Alberta, Edmonton, Alberta T6G 2G5, Canada. E-mail:
[email protected]
PUBLICATION DATA
AIM The purpose of this systematic review was to examine the quality of conduct of experimental
Accepted for publication 19th November 2009.
studies contributing to our empirical understanding of function-based behavioural interventions for stereotypic and repetitive behaviours (SRBs) in individuals with autism spectrum disorders (ASDs). METHOD Systematic review methodology was used to identify relevant articles, to rate the level of evidence and quality of conduct of the studies, and to extract data systematically. RESULTS Ten single case studies examining 17 participants (14 males, 3 females; age 2y 11mo–26y) diagnosed with various ASDs were included. Overall, studies reported decreases in SRBs using behavioural interventions and some collateral increase in desirable behaviours. INTERPRETATION Only a small number of intervention studies for SRBs explicitly state the function of the behaviour; therefore, relatively little is known about the efficacy of SRB interventions in relation to the range of possible behavioural functions. Evidence supporting SRB interventions is preliminary in nature, and caution should be used in choosing and implementing SRB intervention practices for individuals with ASDs.
LIST OF ABBREVIATIONS
ASD NCR PND SRB
Autism spectrum disorder Non-contingent reinforcement Per cent of non-overlapping data Stereotypic and repetitive behaviour
Autism spectrum disorders (ASDs) are a class of neurodevelopmental disorders of unknown aetiology. One of three core features required for a diagnosis of ASD is the demonstration of restricted, repetitive, and stereotyped patterns of behaviours, interests, and activities (including repetitive motor movements, inflexible need for routine, restricted and repetitive interests, or intense, constant interest in particular parts of an object).1 Turner2 divided stereotypic and repetitive behaviours (SRBs) into two categories, low-level and high-level behaviours. Lowlevel behaviours consist of repetitive movement, manipulation of objects, and repetitive self-injurious behaviour, whereas high-level behaviours include object attachment, insistence on routine, repetitive language, and restricted interests.2 SRBs have been documented to encompass a large portion of the behavioural repertoire of individuals with autism.3 Further, SRBs have been shown to interfere with learning4 and can become so intrusive that they affect the individual’s ability to attend and interact, such that they require intervention.5 Individuals with other neurological, cognitive, health, and developmental delays also demonstrate SRBs.6 However, in ASDs, SRBs span a wider topography, with both increased severity and frequency.4 Happe et al.7 have suggested that each of the three core symptoms of ASDs may require individual analysis and separate intervention practices. With this recommendation in mind, this paper examined the inter318 DOI: 10.1111/j.1469-8749.2009.03597.x
ventions directed at the core behaviour of restricted, repetitive, and stereotyped patterns of behaviour, interests, and activities. SRBs are reported to emerge at around 3 to 4 years of age, occurring less frequently in very young children with ASDs.8 Approximately 90% of adolescents and adults with ASDs report engaging in repetitive behaviours.9 Although SRBs may be prominent behaviours over the course of an individual’s lifetime, the form and nature of the behaviours may change over time. Militerni et al.10 reported that young children with ASDs display simple motor and sensory SRBs, whereas older children were found to demonstrate more complex motor and verbal behaviours. Mixed findings have been reported regarding the association between chronological age and developmental level with the form of the SRB. Szatmari et al.11 and Militerni et al.10 reported that lower-functioning children tended to have higher levels of motor and sensory SRBs, whereas Lord and Pickles12 found that neither language nor cognitive age was correlated with SRBs in their sample. Further, SRBs with objects have been linked to a child’s greater capacity for symbolic representation as well as social competence in the second year of life.8 The potential link between SRBs and developmental capacity provides insights into the trajectory of SRBs over an individual’s lifespan. However, the developmental mechanisms and pathophysiology behind SRBs in individuals with ASDs are largely unknown6 (for a theoretical ª The Authors. Journal compilation ª Mac Keith Press 2010
review of SRB pathophysiology see Lewis and Kim13). Yet, despite the lack of firm understanding of the underlying mechanisms and pathophysiology of SRBs, intervention efforts exist to address the negative consequences of SRBs. Closely linked with our understanding of the form of SRBs are the underlying functions of the behaviours. In line with the need for treatment protocols to create effective individualized intervention programmes as determined by the National Research Council,14 is the notion that it is important to design interventions for SRBs that target the functional response of the behaviour rather than the topographical nature of the behaviour alone.4 Several functions have been proposed for SRBs that occur among typically developing children in the first 4 years of life. For example, SRBs can serve to enhance learning through repetition as well as by increasing the predictability of a routine, thus decreasing anxiety.4 Although the function of lifelong SRBs may not be as clear for children with ASDs,6 SRBs are believed to be maintained by a variety of reinforcement contingencies.4 Traditionally, the mechanisms and motivations underlying SRBs were considered to be sensory, relying upon automatic reinforcement contingencies (see Hutt and Hutt15 and Zentall and Zentall16), but, more recently, other forms of reinforcement, such as social positive, non-social positive, and negative reinforcement, have also gained some support in the literature.4 Owing to the variability of not only the possible functions of SRBs, but also the interventions themselves, it is important to understand which functions apply to the target behaviour of interest for a particular individual when considering intervention strategies. Without an analysis of the function of the behaviour, it is difficult to individualize treatment to manipulate the environment effectively not only to extinguish the undesirable behaviour, but also to teach effective appropriate replacement behaviours.17 Also, the frequency at which a behaviour occurs, when and where it occurs, why it occurs, and with what outcomes, are all necessary pieces of the intervention puzzle.18 Intervention practices for SRBs vary in design, intensity, and theory, spanning multiple broad categories of treatment, including behavioural, developmental, and pharmaceutical interventions. Challenges in identifying and utilizing standardized terminology with regard to SRBs19, as well as the heterogeneity of the SRBs themselves and the characteristics of individuals with ASDs, have contributed to difficulties in determining intervention efficacy.20 The implementation of a comprehensive treatment programme often requires high levels of training for personnel, as well as weighty financial and human resources.21 Thus, a better understanding of the gamut of intervention practices for SRBs, the characteristics of the individuals (including age, ASD severity, intellectual ability, etc.) for which any given intervention has demonstrated empirical efficacy, as well as the form and function of SRBs that have been targeted may aid in reducing ineffective use of resources, errors, and any potential harm. Evaluation of studies by using a systematic review methodology, an unbiased and transparent quantitative and qualitative procedure using replicable procedures, can help to determine intervention
What this paper adds • A unique examination of behavioural intervention studies that target SRBs in individuals with autism. • Focus on explicitly stated function, thereby providing insights into a distinctive cross-section of intervention.
efficacy and, thus, best practices for intervention providers.22 Further, statistical methods, such as the calculation of effect size, are often used to examine intervention efficacy.23 It is also important to determine the quality of conduct of a study when critically examining the effects of an intervention.24 Quality assessment via evaluative scales can be used for this purpose in a systematic review.24 Therefore, the purpose of this review is to provide a systematic assessment of behavioural interventions directed at reducing SRBs with identified functions in individuals with autism. Pharmacological interventions, which typically attempt to address the underlying neurobiological mechanisms of SRBs, rather than the behavioural functions, were, therefore, not the focus of this review (see Soorya et al.25 for a recent review of psychopharmacological interventions). For the purpose of our review, we specifically endeavoured to (1) identify the intervention practices used to reduce SRBs in individuals with ASDs for whom the function of the behaviour has been determined and to describe the participants, outcomes, and intervention methods and (2) evaluate the methodological quality of the empirical evidence using quality of conduct evaluation scales set out by the American Academy for Cerebral Palsy and Developmental Medicine (AACPDM),24 supplemented by further criteria reported by Smith et al.26
METHOD Search strategy First, a systematic search was conducted in 20 electronic databases (e.g. MEDLINE, PsycINFO, ERIC); a complete list is presented in see Appendix SI, (supporting information published online) covering educational, psychological, and biomedical areas of study in June 2008 (see Appendix SII, supporting information published online, for a detailed description of the MEDLINE search and a complete list of electronic databases). Second, the reference lists of relevant articles were examined to identify other pertinent studies. Grey literature was not searched; however, unpublished dissertations, theses, and reports retrieved during the search were included. A complete list of the search strings can be obtained from the first author. Study selection: criteria for inclusion Two independent reviewers utilized multiple criteria in screening relevant articles for inclusion in the review. In the case of articles in which multiple experiments were reported, experiments were separated (e.g. Fisher et al.27) and evaluated individually for inclusion. A study must have met the following criteria to be included in the review. (1) The study must have utilized an experimental design including randomized controlled trials, quasi-group designs (i.e. non-randomized comparison group design), or single-participant research Systematic Review
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designs (e.g. multiple baseline design, reversal, alternating treatment design). Studies that utilized a pre-experimental design, such as AB, pre–post test, and case study designs, were excluded (e.g. Arntzen et al.28). (2) Studies utilizing a group design must have examined in the statistical analysis at least 90% of participants enrolled. (3) The study must have included participants of any age diagnosed with autistic disorder, pervasive developmental disorder, or Asperger syndrome. Individuals with a comorbid diagnosis were also included; however, individuals with Rett syndrome or childhood disintegrative disorder were not included because of the significantly different clinical trajectory of these diagnoses. (4) Single case studies must have reported graphical data that could be used to calculate the per cent of non-overlapping data (PND) for at least one of the participants. (5) Group studies must have reported data that allow for the calculation of effect sizes. (6) Studies must include an intervention to ameliorate an SRB. (7) Studies must have explicitly stated or hypothesized the function of the SRB using a method such as a functional analysis. Studies that included a functional analysis but reported inconclusive findings (e.g. Orr et al.29) or failed to explicitly describe a hypothesized function of the SRB (e.g. Fertel-Daly et al.30; Smith et al.31) were excluded. (8) The study must have been reported in the English language and published between the years 1994 and June 2008. The year 1994 was selected as a cut-off in accordance with the last revision of the DSM-IV and implementation of the International Classification of Disease (10th edition). Reasons for exclusion were documented. A complete list of excluded articles is available from the first author.
Quality assessment All 10 included studies utilized single-case research designs. A rating scale developed by the AACPDM24 was used to evaluate the methodological quality of these studies. The scale consists of 14 questions that address selection and description of participants, description of intervention, and accuracy of measurement. A score of 11 to 14 represents a study of strong quality, a score of 7 to 10 represents a study of moderate quality, and a score of 6 or below represents a study of low quality. Second, the Smith et al.26 quality criteria for singlecase research were utilized to provide additional ratings of quality, including measurement of intervention fidelity and generalization of effects. Using these scales, the methodological quality of the studies was assessed and a final numerical score was determined that was then equated to a ranking of relative quality. Two independent reviewers applied the published quality assessment criteria. Interrater reliability was 94.81% on the AACPDM scale and 97.40% on the Smith et al.26 scale. Interrater reliability was determined by dividing the number of agreements by the total number of criteria in the scale and then multiplying this by 100 to obtain a percentage. The total number of criteria in the AACPDM scale was 14, and the total was 7 for the Smith scale.26 Disagreements among reviewers were resolved through dialogue and, if necessary, adjudication by a third reviewer.32 320 Developmental Medicine & Child Neurology 2010, 52: 318–327
Data extraction, analysis, and presentation of results The data from the included studies were synthesized qualitatively. Reported data included participant characteristics and demographic information, design, intervention components, per cent of non-overlapping data (PND), and conclusions. Only data on dependent variables examining SRBs were extracted. Secondary target behaviours (e.g. on task behaviour) are noted in Table I; however, conclusions drawn in the analysis are not related to the possible effects of the intervention with dependent variables other than SRBs. Owing to the wide variation in intervention practices included in this review, no direct statistical comparisons could be made. RESULTS The systematic search of electronic databases resulted in the identification of 1808 citations (Fig. S1, supporting information published online). After removal of duplicates, reviews, and irrelevant articles, 141 studies were retrieved for further review. Ten studies met inclusion criteria, all using singleparticipant designs. The median year of publication of the included studies was 2003, ranging from 2000 to 2007. The 10 articles included one dissertation33 alongside nine peerreviewed journal articles. All 10 studies were conducted in the USA. A list of excluded references and reasons for exclusion can be obtained from the first author. Participant characteristics Seventeen participants were included in the 10 studies, a median sample size of 1. Fifteen participants were diagnosed with autism, one with pervasive developmental disorder, and one with high-functioning autism. Five participants were also reported to have comorbid diagnoses of mental retardation.*34–37 In addition, one participant was reported to have comorbid gastrointestinal difficulties,38 and another was also diagnosed with cerebral palsy.35 The participants were primarily male (n=13) and of school age. However, one toddler, two adolescents, and four adults were also included. Only two studies reported the severity of the participants’ autism symptoms, one reporting mild symptoms5 and one reporting severe symptoms.33 Only one study5 described participant ethnicity, family socio-economic status, and participant intellectual test scores. Target behaviour The authors utilized a variety of experimental functional assessments and informal functional analysis techniques to hypothesize that the function of 15 participants’ SRBs was sensory stimulation. The function of the remaining two participants’ SRBs was proposed to be social attention, while one participant’s SRBs served both an attention and an escape function. Four types of SRB were reported: stereotyped movements, stereotyped manipulation of objects, repetitive use of language, and circumscribed interests.33 Three studies described stereotyped movements for at least one participant. These SRBs are *UK usage: learning disability.
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Children: male (4); mean age 3y 10mo; autism, severe
Children: male (1); mean age 6y; HFA, mild, diagnosed with DSM-IV-TR, CARS, IQ 100, Vineland Adaptive Behaviour 68, Caucasian, upper middle class Children; male (1); mean age 10y; autism; diagnosed with DSM-IV
Cicero33 (USA)
Conroy et al.5 (USA)
Rehfeldt and Chambers37(USA)
Rapp36 (USA)
Kennedy et al.40 (USA)
Carr et al.38 (USA)
Children; male (2); mean age 9y; autism, comorbid mental retardation Adult: male (1); age 23y; autism, comorbid mild mental retardation
Children: male (2), female (2); mean age 7y 3mo: PDD (1), autism (3) Adult: female (1); mean age 26y; autism (one of three total participants), comorbid mental retardation Children: female (1); mean age 7y; autism, comorbid gastrointestinal problems
Ahearn et al.42 (USA)
Britton et al.34 (USA)
Participants (n)
Study
Reversal; level 4
ATD and reversal; level 4
MBD across behaviour function; level 2
ATD; level 4
Reversal; level 4
Reversal; level 4
ATD; level 4
Reversal; level 4
Design
Table I: Summary of study characteristics and their quality
Differential reinforcement and extinction
Matched stimulation and NCR
Functional communication training
Antecedent-based visual cue card strategy
NCR and response interruption
NCR and response blocking
NCR and prompting procedures
Response interruption and redirection
Intervention
Social attention; circumscribed interests: pervasive speech on three topics
Sensory: repetitive language, vocalization
Attention, escape and unidentified source; movement: move ⁄ wave hand
Sensory movements: runs in circles, motor object manipulation, book flipping, object play Sensory movement: hand flapping
Sensory object manipulation: object mouthing
Sensory movements: face rubbing
Sensory; repetitive language: vocalization
Function: type of SRB (DV)
Baseline to intervention: 85.71% ⁄ effective
Attention function: 77.42% ⁄ effective; demand function; 0% floor effect in baseline ⁄ could not determine treatment effect; no attention: 0% ⁄ ineffective treatment No interaction: 80% ⁄ 60– 100% ⁄ effective; toys: 100% ⁄ 100% ⁄ very effective
Response blocking: 100% ⁄ very effective for mouthing DV; 48.15% ⁄ ineffective treatment for mouthing attempts DV; NCR FT 30 and FT 10: 33.3% ⁄ ineffective treatment for mouthing DV Response interruption: 72.86% ⁄ 0– 100% ⁄ effective; NCR: 30% ⁄ 0– 100% ⁄ ineffective treatment; response interruption + NCR: 100% ⁄ 100% ⁄ very effective Floor effect in baseline – 0% ⁄ could not determine effectiveness
50% ⁄ 0–100% floor effect for first phase (0%), 100% for second phase ⁄ could not determine effectiveness
89.47% ⁄ 57.89–100% ⁄ effective
Outcome (PND mean ⁄ rangea ⁄ efficacy)
Appropriate verbal responses
Toy manipulation, music interaction
None
Engagement
Appropriate play
None
None
Appropriate vocalizations
Secondary outcomes
AACPDM: weak (5); Smith (1)
AACPDM: moderate (7); Smith (1)
AACPDM: moderate (7); Smith (1)
AACPDM: moderate (8); Smith (2)
AACPDM: moderate (10); Smith (3)
AACPDM: moderate (7); Smith (1)
AACPDM: moderate (9); Smith (2)
AACPDM: moderate (9); Smith (2)
Methodological quality
Tarbox et al.41 (USA)
a Range provided for studies with two or more participants. AACPDM, American Academy for Cerebral Palsy and Developmental Medicine; ATD, alternating treatment design; CARS, Childhood Autism Rating Scale; DV, dependent variable; HFA, high-functioning autism; NCR, non-contingent reinforcement; PDD, pervasive developmental disorder; PND, per cent of non-overlapping data; FT, Fixed time schedule; MBD, multiple baseline design.
AACPDM: moderate (8); Smith (1) Toy interaction Condition B: 20% ⁄ ineffective treatment; condition C: 40% ⁄ ineffective treatment; condition D: 87.18% ⁄ effective Sensory object manipulation: object mouthing Reversal; level 4
Schedule thinning of response blocking
AACPDM: moderate (8); Smith (1) None Classroom: 100% ⁄ very effective; playroom: 100% ⁄ very effective; outdoor: 100%; very effective Sensory object manipulation: object mouthing
Children; male (1); age 8y; autism, comorbid cerebral palsy and moderate mental retardation Children; male (1); age 4y, autism; Roane et al.35 (USA)
MBD across setting; level 2
Non- contingent access
Methodological quality Secondary outcomes Outcome (PND mean ⁄ rangea ⁄ efficacy) Function: type of SRB (DV) Intervention Design Participants (n) Study
Table I: (Continued)
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rhythmic movements repeated in an invariant manner that is contextually inappropriate39 and included hand flapping,5 face rubbing ⁄ touching,34 and leg or hand movement.40 Repetitive object manipulation (inappropriate and unusual manipulation of objects),39 including object mouthing, was described by another three studies.35,38,41 Repetitive use of language, or a ‘linguistic device or phrase either copied or self generated that is inappropriate and repeatedly used’33 was reported as the target behaviour in two studies.41,42 Finally, circumscribed interests were reported as the target behaviour by one study.35 The circumscribed interests were described as perseverative speech that focused on three topics.
Intervention All interventions evaluated in the included studies were behavioural in nature. For a detailed description of the various forms of intervention see Appendix SIII (supporting information published online). Non-contingent reinforcement (NCR) was the most frequently examined intervention (n=4).33–35,38 NCR was examined in isolation and in combination with other interventions, including response interruption,33 matched stimulation,36 and response blocking.38 Response blocking was examined in one other article in which schedule thinning of the blocking procedure was evaluated.41 Response interruption was also examined by one other study.42 Finally, the efficacy of differential reinforcement on the reduction of SRBs37 and the efficacy of functional communication training40 were examined in one article each. Research design The intervention practices were evaluated using a variety of single-participant research designs. A reversal design was used in six studies,33,36–38,41,42 whereas alternating treatment design5,34 and multiple baseline design35,40 were utilized in two studies each. Measures SRBs were quantified in two ways in the included studies. The frequency of the behaviours was expressed either as a percentage of time engaged in the SRB per interval or session or by frequency counts of the number of observed behaviours or attempts to engage in the target behaviour. Quality of conduct Table II provides the quality of conduct items for the AACPDM scale,24 and the Smith scale,26 as well as an overall summary of study characteristics. Total scores for included studies for both scales can be found in Table I. The 10 included studies achieved scores ranging from 5 to 10 points out of a possible 14 points on the AACPDM quality of conduct rating scale. Nine studies scored between 7 and 10 points equating to a ranking of ‘moderate’. The authors of the scale were contacted regarding how scale rankings, weak, moderate, and strong, were defined. Although the intent of the AACPDM scale is to quantify quality of conduct of a study, the difference between the rankings is somewhat arbitrary; clearly, however, a larger score is indicative of higher quality.
The eight studies in the ‘moderate’ range that scored between 7 and 9 points most frequently lacked blind assessment, tests of statistical analysis, replication of intervention effects across at least three participants, and a minimum of five data points per phase. A score of 11 to 14 points is considered a study of ‘strong’ methodological quality.24 One study33 scored 10 points, nearly reaching this cut-off. The study lacked blind outcome assessors and documentation of a minimum of five data points per phase of the study (e.g. baseline, intervention). Only one study37 obtained a rating of ‘weak’ methodological quality, with a score of 5 out of 14 on the AACPDM scale24 and 1 out of 7 on the Smith scale.26 It is notable that this study lacked operational definitions of the independent variable and a stable baseline that differentiated it from the studies in the ‘moderate’ range. Using the Smith scale26 of quality indicators, the articles scored from 1 to 4 out of 7. The study33 with the highest AACPDM ratings also received the highest ratings on the Smith scale26 (3 ⁄ 7 points). Overall, with regard to the Smith scale,26 studies most frequently lacked specific inclusion–exclusion criteria for participant enrolment, measures of treatment fidelity, and measurement of generalization. For a detailed listing of the criteria and overall percentage scores by criterion for included studies see Table II.
Outcomes PND was calculated for each SRB-related dependent variable (e.g. frequency of SRB, percentage of interval engaged in SRB) or intervention condition (e.g. the Cicero33 dissertation includes multiple interventions). Procedures outlined by Scruggs et al.43 were utilized for computation of PND. PND values were then aggregated across participants in each study. Owing to the heterogeneity of the forms of intervention and their implementation, it was not possible to aggregate PND scores across studies. One study35 was found to have aggregated PND scores above 90%, ranking as ‘very effective’.44 PND values (mean and range) can be found in Table I. A further three studies33,36,38 obtained PND scores in the ‘very effective’ range for at least one dependent variable or intervention condition. ‘Effective’ PND scores (70–90%)44 were found for at least one condition in six studies.33,36,37,40–42 No study obtained a PND score in the 50 to 70% range to obtain a rating of questionable efficacy.44 Finally, four studies33,38,40,41 were rated as having at least one dependent variable PND score below 50%, indicating an ineffective treatment.44 It should be noted that three studies5,34–38,40 graphically reported floor effects in baseline data in at least one condition. This effect led to a PND score of 0%. However, an effectiveness rating was not assigned, as the floor effect may lead to misleading conclusions about the efficacy of the intervention.43 DISCUSSION Overall, the studies included in this systematic review reported positive effects for at least one component of the intervention. The 10 included studies examined a number of unique SRBs, including repetitive motor movements, repetitive language,
circumscribed interests, and repetitive object manipulation. Although the span of SRBs increases the complexity of the variation amongst the studies, it demonstrates an acknowledgement of the range of behaviours that families and professionals are observing among individuals with ASDs. Participant demographic information was infrequently provided (e.g. autism symptom severity, socio-economic status, IQ scores, adaptive behaviour, or developmental ages). Thus, it is difficult to make clear conclusions regarding the characteristics of the individuals who benefit from the interventions and how these individuals differ. However, all studies reported high average baseline frequencies of SRB, indicating that about 60% of the documented baseline interval data consisted of time spent engaging in SRBs. For those studies reporting the number of SRBs per minute interval, up to six behaviours a minute during baseline were documented. This indicates that SRBs were absorbing a substantial amount of the child’s daily time and energy in classroom, community, and home settings. Interesting findings were documented with regard to NCR implementation. NCR was evaluated alone36 and in combination with response interruption,33 response blocking,38 prompting procedures,34 and matched stimulation.33,46 Although Roane et al.35 reported positive findings of non-contingent access to food to reduce repetitive object mouthing (supported by 100% PND scores in all conditions), the longterm clinical utility, social validity, and ethical use of sugary food, such as marshmallows and hard candy, to reduce the behaviour is questionable. It is also questionable whether or not the repetitive behaviour had in fact been reduced or whether the mouthing behaviour had only been redirected from objects to food. Cicero33 examined NCR in combination with response interruption. NCR alone was found to be ineffective in significantly reducing SRBs. Further, the combination of NCR with response interruption was found to be no more effective than response interruption alone. This indicates the possibility that response interruption, rather than NCR, was primarily responsible for the decrease in SRBs when the two were combined. Similarly, findings from Carr et al.38 indicate that NCR failed to reduce SRBs until combined with response blocking, whereas initial response blocking was more successful. These findings are supported by our PND analysis, which indicated that NCR was an ‘ineffective intervention’ in both of the above-mentioned studies. Although Britton et al.34 do present positive effects for NCR, this effect was found only when combined with a prompting procedure to encourage the child to access the non-contingent reinforcer. The authors note that this ‘relatively minor manipulation of NCR negated its effectiveness’.34 However, Rapp36 provides evidence to the contrary, reporting NCR incorporating matched stimulation (audio stimulation from toys) to be effective in reducing repetitive language. These mixed results across nine participants on the autism spectrum indicate that further research into the efficacy of NCR with SRBs that are maintained by sensory consequences is required before conclusions can be made. Functional communication training,40 differential reinforcement,37 and an antecedent-based visual cue card interSystematic Review
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Table II: Methodological characteristics of single case studies Number of studies (%), n=10 AACPDM (2008) quality components (1) The participant(s) are well described to allow comparison with other studies or with the reader’s own patient population (2) Independent variables were operationally defined to allow replication (3) Intervention conditions operationally defined to allow replication (4) Dependent variables operationally defined as dependent measures (5) Interrater ⁄ intrarater reliability of dependent measures assessed before and during each phase of the study (6) Outcomes assessor blind (7) Stability of data demonstrated in baseline (8) Type of single-participant research design was clearly and correctly stated (9) Adequate number of data points in each phase (minimum 5) (10) Intervention replicated across three or more individuals (11) Authors conducted and reported visual analysis (12) Graphs used for visual analysis follow standard conventions (13) Authors report tests of statistical analysis (14) All criteria met for statistical analysis Smith et al. (2007) quality components (1) Use of single-case experimental design (2) Specific inclusion and exclusion criteria for enrolment in study along with drop-outs and intervention failures (3) Well-defined samples of participants in the study (i.e. standardized diagnostic tests, standardized intelligence tests, adaptive behaviour) (4) Replication of intervention across three or more participants (5) Assessment of generalization of intervention effects to at least one other setting or maintenance of effects over time (6) Measurement of outcome conducted blind to the purpose of the study (7) Fidelity of intervention implementation monitored through direct observation
10 (100)
9 (90) 9 (90) 10 (100) 10 (100)
0 (0) 5 (50) 9 (90) 1 (10) 2 (20) 1 (10) 9 (90) 1 (10) 1 (10) 10 (100) 0 (0)
2 (20)
2 (20) 0 (0)
0 (0) 3 (30)
AACPDM, American Academy for Cerebral Palsy and Developmental Medicine.
vention5 were evaluated in one study each. It is notable that floor effects in the baseline data of the visual cue card intervention5 negated our ability to determine the effectiveness of the intervention based on PND calculations.44 Further, the study examining functional communication training40 also reported floor effects in one of three intervention conditions; thus, we were again unable to determine efficacy from PND scores. This is unfortunate because baseline data indicate that SRBs ranged from 0% to nearly 100% per interval; however, during functional communication training intervention, the participant engaged in SRBs for only approximately 0 to 10% of the intervals. Therefore, the data indicate that a substantial treatment effect occurred; however, this is not repre324 Developmental Medicine & Child Neurology 2010, 52: 318–327
sented in the PND data. This study is of interest because it is the only included study that examined an SRB that had been determined through functional analysis to be reinforced by multiple factors, including social attention and negative reinforcement. The effect of differential reinforcement of alternative behaviour in combination with extinction procedures on socially maintained SRBs was examined in one of the included studies.37 The authors report that differential reinforcement of alternative behaviour and extinction successfully reduced perseverative speech in an adult male diagnosed with autism and mild mental retardation. This conclusion is supported by our PND analysis, which indicates that the intervention was ‘effective’ (85.71% PND). However, this study was scored as being ‘weak’ in methodological quality, achieving a score of 5 out of a possible 14 on the AACPDM scale24 and a score of 1 out of 7 on the Smith scale.26 Owing to independent variables and intervention conditions with poor operational definitions, the ability of independent researchers to replicate the effects of this intervention was questionable. Further, the lack of stability in baseline data and the lack of replication of the intervention effects reduce the external validity. Response interruption intervention was examined by two of the included studies,33,42 both of which were determined to be of moderate methodological quality (AACPDM).23 One study33 achieved an AACPDM score only 1 point short of a rating of ‘strong’ methodological quality, the highest score of any included study. Further, our PND scores for this response interruption indicated a ‘very effective’ intervention33,42 across the two studies. However, there are several limitations to this finding. The implementation of response interruption intervention requires the ongoing daily involvement of trained staff members to physically administer the interruption procedure to an individual. It should be noted that this form of one-on-one intensive intervention can necessitate high levels of human and financial resources and may not be feasible to implement or to provide over the long term. Further, Reichow et al.23 advise that promising evidence-based practices are to be used with caution and should be monitored closely until further supportive evidence is gathered. In using the example of response interruption, only one of the two studies examined generalization or follow-up levels of SRB frequency.42 The generalization probes for three of the four participants provided in textual data indicate a drop in SRB level from 22 to 64% between pre- and posttreatment probes across participants. These data indicate potential positive effects extending 1 month beyond the limited time frame of intervention conditions. However, it is important to note that all three studies examined individuals with SRBs for whom the function of the behaviour was determined to be sensory stimulation. Thus, it is possible that efficacy of the intervention may vary with topographically similar SRBs that serve a different function (e.g. socially maintained or negatively reinforcing). In addition this study represents a small sample of four children who were poorly described, which prohibits determination of individuals for whom this intervention is best suited.
In several of the studies, a component of the intervention was to teach parents, caregivers, or teachers to implement the intervention. Ahearn et al.42 and Conroy and et al.5 taught the participants’ classroom teacher and the teaching assistant to implement the intervention in novel academic settings. Social validity based on the teacher’s report was positive. Similarly, social validity in the Carr et al.38 study, in which interventionists expanded the implementation of NCR to different settings and to new therapists, was also high. The study by Tarbox et al.41 was the only one to include parent training as a component of the intervention. The training included descriptions and models of the intervention procedure. Parents were also provided with verbal feedback regarding their implementation of the intervention throughout the process. Involving key members of the child’s environment, such as parents and teachers, is a notable feature of these reports and has been found in other research45 to help maintain the positive results of children’s treatment. As such, this component of these studies should be highlighted.
Recommended clinical practice The empirical evidence for a benefit of interventions for SRBs in individuals with ASDs is preliminary in nature; however, positive findings are reported for a wide number of interventions as well as in participants of various ages, developmental levels, ASD symptom severity, and ethnicity. Multiple factors must be taken into account when evaluating the evidence to support the implementation of a particular intervention to reduce SRBs in an individual with ASDs. Although many of the interventions reported in the literature probably do not cause harm, some may be ineffective. A handful of studies examined various combinations or versions of similar intervention practices,34,37,41 whereas only a few directly compared the efficacy of different intervention practices.33,36,38 Owing to the limited evidence comparing intervention methods, no one intervention should be used at the exclusion of another.46 This synthesis of the literature provides limited information about where time, energy, and financial resources should be invested to deliver the most positive outcomes. Decisions regarding the implementation of these practices should be made with caution, taking into account the values and needs of the family, the unique characteristics of the child, and the clinical expertise of professionals in the field.47 For any intervention to be effective, it is important that professionals be sensitive to the needs of the individual child and family in question.48 Examining the function of the SRB is part of the individualization of intervention services. The function of SRBs for individuals in the included studies was frequently determined to be a need for unique sensory input (n=15). Thus, the clinical expertise of occupational therapists who work with individuals with ASDs may prove to be a valuable resource in the decision-making process. Further, the interventions included in this review were behavioural in nature. Consultation with a Board Certified Behaviour Analyst (BCBA) may aid in developing and implementing an appropriate intervention.
Study strengths and limitations A strength of this systematic review is the focus on intervention studies that explicitly state the function of the targeted SRBs. The literature on SRB intervention is quite widespread; however, it is apparent that relatively few intervention studies examine behavioural function, a necessary piece of information for effective intervention by clinicians. A further strength of the paper is the execution of a comprehensive search of indexed literature and theses ⁄ dissertations, which was conducted to retrieve studies that examined the efficacy of interventions for SRBs in individuals with ASDs. This search was probably successful in retrieving the majority of relevant articles. However, we acknowledge that we did not search sources of grey literature and we excluded studies written in languages other than English, which may have resulted in the omission of relevant contributions. Further, because this review focused on studies that explicitly identified the function of the SRB, studies that implied but did not explicitly state a function (e.g. sensory interventions such as weighted vests), or studies that described intervention methods grounded in alternative explanatory models (e.g. pharmaceuticals such as selective serotonin reuptake inhibitors), were excluded. A limitation of the present findings is that all of the intervention studies included in this review were single-participant research designs. Although single-case research is a rigorous, scientific methodology used to define basic principles of behaviour and establish evidence-based practices,49 it is often seen as a starting point for formulating and understanding how to apply new interventions systematically.26 Strengths of single-participant research are that it (1) yields evidence that a technique has a clear, replicable effect on a specific behaviour in one or several individuals; (2) allows for individualization of intervention across participants; (3) measures progress over multiple time points, enabling careful analysis of intervention; and (4) requires fewer resources than clinical trials.26 Single-subject methods are particularly well suited to study individuals with ASDs, whose characteristics and life circumstances are exceedingly heterogeneous in nature. This heterogeneity creates substantial problems when scientists attempt to use group-based methodology to address questions about the effectiveness of treatments. In fact, group-based studies designed to determine the effectiveness of intervention for individuals with ASDs are in the minority; there exists a much more substantial body of research using primarily single-case design methods,50 especially in the area of defining interventions. This limitation, therefore, speaks more to the state of the science in SRB research. Future directions Looking forward, we have several recommendations for the evaluation of interventions for SRBs in individuals with ASDs, based upon review of the literature. No intervention study obtained a ranking of ‘strong’ in methodological quality. However, one study obtained a score of 10 out of 14, one point below a rating of ‘strong’. This study differed from stud-
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ies scoring lower rankings by demonstrating stable baseline data, reporting appropriate visual analysis, and demonstrating replication of the intervention effects across three or more individuals. However, critical methodological components including use of blind raters, reporting of an adequate number of data points per design phase, and appropriate statistical analysis were lacking. Several commonly implemented interventions for individuals with ASDs were not included in this review. No study examining the effects of diet modification, the use of sensory ‘diets’, or alternative medicines was found in the systematic search of the literature, with the exception of one study examining the use of Chinese medicine with children with ASDs.51 However, this study utilized a research design of low quality and, thus, was not included in the review. Although these controversial interventions52 have yet to develop a base of empirical evidence to support their use to reduce SRBs in individuals with ASDs, they are being implemented in homes around the world. In the pursuit of evidence-based intervention practices for SRBs, a progression to more rigorous experimental designs (group comparison designs) would create a clearer picture of the effectiveness of these various intervention practices. However, owing to practical (funding, time constraints, etc.) and ethical limitations, group designs can be difficult to implement. To meet the standards for ‘promising’ and ‘established evidence-based practices’,23 further replications of intervention effects in single-case research could also provide greater
evidential support. The implementation of randomization procedure in both multiple baseline and alternating treatment designs would also increase the methodological rigor of single-case designs.
CONCLUSIONS The 17 participants involved in these studies demonstrated high baseline levels of SRBs. These high frequencies, alongside the teacher and parent reports, indicated that these behaviours were interfering with the individuals’ ability to engage appropriately in their environment. Overall, positive effects were reported for behavioural interventions to reduce SRBs maintained by a variety of identified functions displayed by individuals with ASDs; however, there are several limitations to these findings. This evidence is preliminary in nature because of the small number of participants in the 10 studies and the heterogeneity of both the population and the interventions themselves. Caution should be used in choosing and implementing interventions to ameliorate SRBs in order to reduce the use of ineffective treatment, thus wasting valuable resources. Further research is required to examine the array of behavioural, sensory, pharmaceutical, and developmental, interventions for SRBs based upon the function of the behaviour. ONLINE MATERIAL Additional material may be found in the online version of this article.
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