Impact of Social Communication Interventions on Infants and Toddlers With or At-Risk for Autism

Abstract

This is a systematic review of the impact of communication interventions on the social communication skills of infants and toddlers with or at-risk for autism spectrum disorder (ASD). A priori clinical questions accompanied by specific inclusion and exclusion criteria informed the extensive literature search that was conducted in multiple databases (e.g., PubMed). Twenty-six studies were accepted for this review. Outcomes were reported by social communication category (i.e., joint attention, social reciprocity, and language and related cognitive skills) and communication developmental stage (i.e., prelinguistic, emerging language). Primarily positive treatment effects were revealed in the majority of outcome categories for which social communication data were available. However, the presence of intervention and outcome measure heterogeneity precluded a clear determination of intervention effects. Future research should address these issues while also evaluating multiple outcomes and adding a strong family component designed to enhance child active engagement.

Keywords

autism autism spectrum disorder social communication pervasive developmental disorder speech-language pathology intervention

In 2012, the American Speech-Language-Hearing Association’s (ASHA’s) National Center for Evidence-based Practice was charged with developing an evidence-based systematic review (EBSR) on the impact of communication interventions for infants and toddlers with or at-risk for ASD in collaboration with experts in the field. An EBSR addresses unambiguous and specific questions on a particular topic; clearly explains the methods and criteria used to locate and select studies for inclusion; and entails reviewing, critiquing, and integrating pertinent information from the selected studies in an effort to provide a synthesis of the current best evidence (Dollaghan, 2007).

Previous systematic reviews have examined the impact of communication treatments on various skill areas in wide age groups of children with ASD (e.g., National Research Council [NRC], 2001; Schertz, Reichow, Tan, Vaiouli, & Yildirim, 2012; Wallace & Rogers, 2010). In reviews that addressed infants and toddlers, lack of empirically validated treatments for infants and toddlers with ASD (Wallace & Rogers, 2010) and great heterogeneity in findings (e.g., Schertz et al., 2012) precluded ascertaining generalized treatment effects. Clearly, a closer examination of the evidence pertaining to social communication interventions used with young children is warranted.

To better elucidate the treatment effects of social communication interventions, a framework devised by ASHA was adopted (ASHA, 2006). The framework groups intervention goals by social communication outcome categories (i.e., joint attention, social reciprocity, language and related cognitive skills, behavior and emotional regulation) across communication developmental stages (i.e., prelinguistic, emerging language). The social communication outcome categories represent core areas of difficulty for individuals with ASD, whereas the selected developmental stages reflect the age of the population discussed in this EBSR. Joint attention is establishing shared attention, social reciprocity entails maintaining interactions by taking turns, language and related cognitive skills applies to the use and understanding of nonverbal and verbal communication, and behavioral and emotional regulation is the successful regulation of one’s emotions and behaviors (ASHA, 2006). In regard to the communication developmental stages applicable to infants and toddlers, prelinguistic pertains to the use of nonverbal communicative strategies, such as gestures; and emerging language is the burgeoning use of verbal language (ASHA, 2006). The aim of this EBSR was to further evaluate the impact of communication interventions on social communication skills of infants and toddlers with ASD aged 36 months or less. The clinical questions for this EBSR follow:

Clinical Question 1: What are the effects of communication interventions on joint attention outcomes for children 36 months old or less at-risk for or diagnosed with ASD?

Clinical Question 2: What are the effects of communication interventions on social reciprocity outcomes for children 36 months old or less at-risk for or diagnosed with ASD?

Clinical Question 3: What are the effects of communication interventions on language and related cognitive skill outcomes for children 36 months old or less at-risk for or diagnosed with ASD?

Clinical Question 4: What are the effects of communication interventions on behavioral and emotional regulation outcomes for children 36 months old or less at-risk for or diagnosed with ASD?

Method

To complete this EBSR, a multi-step approach was taken including (a) identification of peer-reviewed articles that address the population of interest and clinical questions; (b) evaluation of the methodological rigor of accepted studies; (c) grouping outcomes as prelinguistic or emerging language within one of the following areas: joint attention, social reciprocity, language and related cognitive skills, or behavioral and emotional regulation; (d) computing effect sizes and assigning associated magnitude of effect descriptors; and (e) assessing the findings in relation to the clinical questions. One author conducted a literature search in 25 electronic databases (e.g., PubMed, ERIC, Research Autism) using key words related to autism, autism spectrum disorder (ASD), pervasive developmental disorder (PDD), speech-language pathology, and treatment (the complete list of databases, key words, and search strategy is available on request). Two authors independently assessed the titles and abstracts of all articles. The references of all full-text articles were scanned to identify additional relevant studies and a search for prolific authors was also completed. Two authors also independently assessed each included study for methodological rigor; any disagreements about critical appraisal ratings were resolved via consensus. Single-subject design studies were assessed using an adapted version of the Single Case Experimental Design (SCED) scale (Tate et al., 2008) and group studies were assessed using ASHA’s critical appraisal scheme (Cherney, Patterson, Raymer, Frymark, & Schooling, 2008; Mullen, 2007). See Supplemental Materials Tables 1 and 2 for further information regarding the critical appraisal processes.

Table 1.

Clinical Question 1: Prelinguistic-Joint Attention Findings.

	Single-subject study outcomes				Group study outcomes
Single-subject studies	ES (NAP)	ES magnitude	p value	Group studies	ES (d)	ES magnitude	p value
Joint attention intervention				Autism 1-2-3 project
Jones, Carr, and Feeley (2006)	0.39–1.00	Medium–large	NR	Wong and Kwan (2010)	−3.13	Large	.001
Krstovska-Guerrero and Jones (2013)	1.00	Large	NR	Brief Early Start Denver Model
Rocha, Schreibman, and Stahmer (2007)	0.72–0.97	Medium–large	NR	Rogers et al. (2012)	0.00–0.13 (2/3 CI:NS)	Small	NR
Joint attention-mediated learning				Hanen’s More than Words®^a
Schertz and Odom (2007)	0.00–0.98	Small–large	NR	Carter et al. (2011)	0.8–0.24 (CI:NS)	Small	NR
Reciprocal imitation training				Interpersonal synchrony vs. non-interpersonal synchrony
Ingersoll and Schreibman (2006)	0.61–0.76	Medium	NR	Landa, Holman, O’Neill, and Stuart (2011)	0.42–0.89	Medium–large	.08–.41
Simultaneous communication				Joint attention-mediated learning
Kouri (1988)	1.00	Large	p < .05	Schertz, Odom, Baggett, and Sideris (2013)	0.70–1.39	Large	1/3 NS
Social engagement intervention
Vernon, Koegel, Dauterman, and Stolen (2012)	0.81–0.99	Medium–large	NR

Note. ES = effect size; NAP = non-overlap of all pairs; CI = confidence interval; NR = not reported; NS = not significant.

Only treatment follow-up data (i.e., maintenance data) were reported in this study.

Table 2.

Clinical Question 2: Prelinguistic-Social Reciprocity Findings.

	Single-subject study outcomes				Group study outcomes
Single-subject studies	ES (NAP)	ES magnitude	p value	Group studies	ES (d)	ES magnitude	p value
Joint attention-mediated learning				Autism 1-2-3 project
Schertz and Odom (2007)	0.35–0.74	Medium	NR	Wong and Kwan (2010)	NR	NR	.008
Peer-mediated intervention				Brief Early Start Denver Model
Goldstein, Kaczmarek, Pennington, and Shafer (1992)	0.22–0.57	Small–medium	NR	Rogers et al. (2012)	−0.07 (CI:NS)	Small	NR
Simultaneous communication				Joint attention-mediated learning
Kouri (1988)	0.92–1.00	Large	p < .05	Schertz, Odom, Baggett, and Sideris (2013)	0.55	Medium	>.05
Social engagement intervention
Vernon, Koegel, Dauterman, and Stolen (2012)	0.94–0.98	Large	NR

Note. ES = effect size; NAP = non-overlap of all pairs; CI = confidence interval; NR = not reported; NS = not significant.

Interrater reliability associated with the sifting of titles and abstracts as well as the critical appraisal process were determined using Cohen’s kappa (κ; Cohen, 1988) and weighted κ. Cohen’s κ was used in instances in which only two rating options equal in weight were available for selection. Weighted κ was applied to critical appraisal items that had hierarchical rating options (i.e., sampling process, random allocation, controlling for order effects, precision). The following is Landis and Koch’s (1977) scale for interpreting κ which was used to categorize the strength of the agreement: poor agreement (<0.00), slight agreement (0.00–0.20), fair agreement (0.21–0.40), moderate agreement (0.41–0.60), substantial agreement (0.61–0.80), and almost perfect agreement (0.81–1.00). Percent agreement was reported when κ could not be computed or when the kappa value was zero.

For inclusion in this EBSR, studies had to be peer-reviewed and experimental or quasi-experimental. Furthermore, studies had to examine the impact of communication interventions on social communication skills of children 36 months old or younger at-risk for or diagnosed with ASD. For the purposes of this review, the ASD category included the following diagnostic labels: Asperger syndrome, autism, autistic disorder, PDD, and pervasive development disorder–not otherwise specified (PDD-NOS). Accepted studies were written in English and published after 1970. Studies with mixed populations or mixed ages were excluded unless data could be separated for analyses. In addition, only participant data from single-subject design studies that integrated a control mechanism (i.e., studies with a withdrawal or reversal phase and/or multiple baseline design studies) were included; consequently, multiple baseline design studies across participants without a withdrawal or reversal phase which included only one participant who met our age criterion were not accepted as they became an AB design. Both single-subject and group design studies were included as the former provides information about the impact of an intervention in consideration of an individual’s unique abilities, whereas the latter are used to evaluate the generalizability (i.e., external validity) of a treatment’s effects.

Interventions in included studies were required to contain at a minimum a description of the training method(s) or techniques from which they were comprised. Study findings were classified by social communication outcome categories (i.e., joint attention, social reciprocity, language and related cognitive skills, and behavioral and emotional regulation), and then further categorized into communication developmental stages (i.e., prelinguistic, emerging language) using the framework devised by ASHA (2006). So, examples of outcomes classification labels include prelinguistic-joint attention, prelinguistic-social reciprocity, and emerging language–language and related cognitive skills. Key participant information (e.g., age), intervention variables (e.g., duration) and outcomes data (e.g., joint attention), including maintenance and generalization findings, were extracted from each study. Given the importance of the ecological validity of findings, qualitative data gathered from surveys and observations completed by caregivers and non-participating clinical professionals was extracted, if reported, to evaluate social validity.

Statistical significance and effect size were reported if available in the study or calculated if applicable raw data were provided. For single-subject design studies, linear graphs were visually analyzed to compute the non-overlap of all pairs (NAP; Parker & Vannest, 2009) effect size for intervention outcomes. Conventions for applying NAP, including classification of the magnitude of the effect size (i.e., small = 0–0.31, medium = 0.32–0.84, and large = 0.85–1.00), were adapted from Parker and Vannest (2009). For group studies, the calculated effect size metric was Cohen’s d (Cohen, 1988). For the purpose of assigning descriptive labels to effect sizes reported in group studies, the following modified version of Cohen’s classification of effect size magnitude was used: small = 0 to 0.34; medium = 0.35 to 0.64; and large = 0.65 or greater with positive effect sizes favoring the intervention. When provided or calculable, confidence intervals were also reported for group study effect sizes. For both single-subject and group studies, results were considered statistically significant if the p value was less than .05. For group studies, effect size confidence intervals that contained the null effect (i.e., d = 0) were not considered to be statistically significant. Both effect sizes (and their confidence intervals when calculable) and p values were reported because sample size has a greater impact on p-value calculation than effect size computation (Borenstein, Hedges, Higgins, & Rothstein, 2009). Therefore, a treatment effect may be present, but not appear statistically significant based on the p value due to a sample size that is too small to detect a treatment effect (i.e., the study does not have enough power).

Results

Twenty-six studies (n = 19 single-subject and 7 group studies) from 1,379 identified citations were accepted for this EBSR. The full list of excluded studies and reason(s) for ineligibility (e.g., not population or age of interest) is available on request. Substantial interrater reliability (κ = 0.69; Cohen, 1988) was noted between the authors who sifted abstracts and full-text articles. Kappa ratings for critical appraisal items from both study designs ranged from slight agreement (κ = 0.13) to substantial agreement (κ = 0.77), whereas percent agreement ranged from 84% to 100%. Most critical appraisal items were adequately addressed in accepted single-subject design and group studies. See Supplemental Materials Tables 1 and 2 for more information about study quality.

A total of 427 participants, who were aged 10 to 36 months and diagnosed with autism, ASD, PDD-NOS, or Asperger syndrome, were included in this EBSR. Participant race/ethnicity, which was reported in a few studies (Carter et al., 2011; Dawson et al., 2010; Landa, Holman, O’Neill, & Stuart, 2011; Rogers et al., 2012; Vernon, Koegel, Dauterman, & Stolen, 2012; Vismara, Colombi, & Rogers, 2009), included American Indian, Alaskan Native, Asian, Black, Hispanic or Latino, Multiracial, and White. See Supplemental Materials Table 3 for additional participant and service delivery data as well as descriptions of interventions.

Table 3.

Clinical Question 3: Prelinguistic-Language and Related Cognitive Skills Findings.

	Single-subject study outcomes				Group study outcomes
Single-subject studies	ES (NAP)	ES magnitude	p value	Group studies	ES (d)	ES magnitude	p value
Early Start Denver Model				Brief Early Start Denver Model
Vismara, Colombi, and Rogers (2009)	0.20–1.00	Small–large	NR	Rogers et al. (2012)	−0.14 (CI:NS)	Small	NR
Pivotal response training				Hanen’s More than Words ®^a
Steiner, Gengoux, Klin, and Chawarska (2013)	1.00	Large	NR	Carter et al. (2011)	−0.15 to 0 (CI:NS)	Small	NR
Reciprocal imitation training
Ingersoll and Schreibman (2006)	0.00–1.00	Small–large	NR
Reciprocal imitation training vs. video modeling
Cardon and Wilcox (2011)	0.71–0.85 (RIT)	Medium	NR
	0.73–0.98 (VM)	Medium–large	NR
Simultaneous communication
Kouri (1988)	0.83–1.00	Large	M
UCLA treatment model
Smith, Buch, and Gamby (2000)	0.71–1.00	Medium–large	NR
Video modeling imitation training
Cardon (2012)	0.93–1.00	Large	NR

Note. ES = effect size; NAP = non-overlap of all pairs; RIT = reciprocal imitation training; VM = video modeling; M = mixture of statistically significant and non-statistically significant findings; CI = confidence interval; NR = not reported; NS = not significant.

Only treatment follow-up data (i.e., maintenance data) were reported in this study.

Study Outcomes

Included studies examined various social communication outcomes across prelinguistic and emerging language developmental stages to address three of four a priori clinical questions. Study outcomes were classified as prelinguistic-joint attention (Clinical Question 1; n = 11 studies), prelinguistic-social reciprocity (Clinical Question 2; n = 7 studies), prelinguistic-language and related cognitive skills (Clinical Question 3; n = 9 studies), and emerging language–language and related cognitive outcomes (Clinical Question 3; n = 18 studies). No outcomes in the accepted studies fell into the behavior and emotional regulation category (Clinical Question 4). For most clinical questions, conclusions about the relationship between study quality and study outcomes could not be drawn because study quality was similar across studies. For Clinical Question 2, however, one of the single-subject studies (Kouri, 1988) had larger treatment effects but lower study quality than the other two single-subject studies in this category (Goldstein, Kaczmarek, Pennington, & Shafer, 1992; Schertz & Odom, 2007). As indicated in at least one study of each of the four aforementioned outcome categories, caregivers overwhelmingly were satisfied with the interventions and associated outcomes. Supplemental Materials Table 4 provides a summary of findings across social communication outcome goals and communication developmental stages. Additional information about study findings by communication developmental stage and social communication categories is elucidated below.

Table 4.

Clinical Question 3: Emerging Language–Language and Related Cognitive Skills Findings.

	Single-subject study outcomes				Group study outcomes
Single-subject studies	ES (NAP)	ES magnitude	p value	Group studies	ES (d)	ES magnitude	p value
Behavioral intervention				Autism 1-2-3 Project
Williams, Pérez-González, and Vogt (2003)	1.00	Large	NR	Wong and Kwan (2010)	NR	NR	.01–.04
Developmental, social pragmatic intervention				Brief Early Start Denver Model
Ingersoll, Dvortcsak, Whalen, and Sikora (2005)	0.71–0.86	Medium–large	NR	Rogers et al. (2012)	−0.24 to 0.24 (CI:NS)	Small	NR
Discrete trial training vs. mand training				Early Start Denver Model
Jennett, Harris, and Delmolino (2008)	0.94–1.00 (DTI)	Large	NR	Dawson et al. (2010)	0.58–0.66 (CI: 2/4 NS)	Medium–large	.03–.06
	1.00 (MT)	Large	NR	Eclectic intervention vs. applied behavioral analysis
Early Start Denver Model				Zachor and Itzchak (2010)	−0.18 to 0.59 (CI: 3/4 NS)	Small–medium	NR
Vismara, Colombi, and Rogers (2009)	0.20–1.00	Small–large	NR	Hanen’s More than Words®^a
Enhanced milieu teaching				Carter et al. (2011)	−0.26 to 0.42 (CI:NS)	Small–medium	NR
Kaiser, Hancock, and Nietfeld (2000)	0.76–0.87	Medium–large	NR	Interpersonal vs. non-interpersonal synchrony
Peer-mediated intervention				Landa, Holman, O’Neill, and Stuart (2011)	0.49	Medium	.18
Goldstein, Kaczmarek, Pennington, and Shafer (1992)	0.24–0.61	Small–medium	NR
Pivotal response training vs. discrete trial training
Schreibman, Stahmer, Cestone Barlett, and Dufek (2009)	0.47–0.97	Medium–large	NR
Schreibman, Stahmer, Cestone Barlett, and Dufek (2009)	−0.28 to 0.59	Small–medium	NR
Reciprocal imitation training
Ingersoll and Schreibman (2006)	0.00–0.86	Small–large	NR
Simultaneous communication
Kouri (1988)	0.00–1.00	Small–large	M
Social engagement intervention
Vernon, Koegel, Dauterman, and Stolen (2012)	0.81–0.94	Medium–large	NR
Teaching strategy intervention
Kashinath, Woods, and Goldstein (2006)	0.48–0.96	Medium–large	NR
UCLA treatment model
Smith, Buch, and Gamby (2000)	0.00–1.00	Small–large	NR

Note. ES = effect size; NAP = non-overlap of all pairs; NR = not reported; DTI = discrete trial instruction; MT = mand training; M = mixture of statistically significant and non-statistically significant findings; CI = confidence interval; NS = not significant.

Only treatment follow-up data (i.e., maintenance data) were reported in this study.

Prelinguistic-joint attention findings

Table 1 provides a detailed list of interventions and associated outcomes for the 11 studies of prelinguistic-joint attention (Clinical Question 1). Findings from single-subject studies overwhelmingly indicated improvement in prelinguistic-joint attention skills across the variety of treatment categories. The associated effect sizes ranged from small to large in magnitude (NAP = 0–1.00), with the bulk being in the medium to large range (NAP = 0.39–1.00). The greatest variability in treatment effect (NAP = 0–1.00) was noted across participants who received various joint attention interventions (Jones, Carr, & Feeley, 2006; Krstovska-Guerrero & Jones, 2013; Rocha, Schreibman, & Stahmer, 2007; Schertz & Odom, 2007). No effect size confidence intervals were provided or calculable and no p values were reported. All studies except Kouri (1988) reported maintenance and generalization findings; overall, target behaviors were maintained following treatment and skills were demonstrated across a variety of people and settings.

Group study effect sizes were mainly medium to large in magnitude (d = −3.13 to 1.39), with the exception of the findings associated with the Brief Early Start Denver Model (d = 0–0.13: Rogers et al., 2012). In most instances, the findings were not statistically significant. However, in the case of Wong and Kwan (2010), the treatment effect associated with the Autism 1-2-3 Project intervention was in favor of the control group. Growth rate difference effect sizes were medium to large for a comparison of interpersonal synchrony and non-interpersonal synchrony interventions (Landa et al., 2011); yet, they were accompanied by non-statistically significant p values. In addition, within-group findings revealed gains from pre- to post-test only for the intervention group (Landa et al., 2011). The majority of maintenance findings as reported in studies of Hanen’s More than Words® (Carter et al., 2011) and a joint attention-mediated learning (Schertz, Odom, Baggett, & Sideris, 2013) intervention were small to large in magnitude (d = 0.08–1.18) and accompanied by primarily non-statistically significant p values; the largest effect sizes were associated with the joint attention intervention. Maintenance findings from the Landa et al. (2011) comparative study revealed large effect sizes (d = 0.81–1.56) at post-treatment and medium to large effect sizes (d = 0.41–0.68) for growth rate differences between the groups; p values were not statistically different for the post-treatment or growth rate difference data. No generalization findings were reported.

Prelinguistic-social reciprocity findings

Findings from single-subject studies that addressed prelinguistic-social reciprocity outcomes (Clinical Question 2; see Table 2) were small to large in effect size magnitude (NAP = 0.22–1.00), with findings from the simultaneous communication (Kouri, 1988) and social engagement (Vernon et al., 2012) interventions falling solely in the large range (i.e., NAP = 0.92–1.00). No p value or effect size confidence interval information was reported. Maintenance and generalization of prelinguistic-social reciprocity findings were limited to a study of a joint attention-mediated learning (Schertz & Odom, 2007) intervention. Findings revealed that the skills were maintained at levels higher than what was seen during baseline and that generalization occurred across a variety of settings.

Much variability existed in group study findings (see Table 2), with a significant p value (p = .008) associated with the Autism 1-2-3 Project intervention (Wong & Kwan, 2010), a negligible effect size (d = −0.07) accompanied by a confidence interval containing the null effect reported in the study of Brief Early Start Denver Model (Rogers et al., 2012), and a medium (d = 0.55), but not statistically significant finding from a joint attention-mediated learning intervention (Schertz et al., 2013). A small (d = 0.10) and non-statistically significant maintenance finding was reported in Schertz et al. (2013). No generalization findings were reported.

Prelinguistic-language and related cognitive skills findings

Table 3 provides a detailed list of interventions and associated outcomes in the prelinguistic-language and related cognitive skills category (Clinical Question 3). The effect sizes from single-subject studies were in the small to large range (NAP = 0–1.00), with most falling in the medium to large range for the following interventions: pivotal response training (Steiner, Gengoux, Klin, & Chawarska, 2013), video modeling imitation training (Cardon, 2012), University of California, Los Angeles (UCLA) treatment model (Smith, Buch, & Gamby, 2000), and simultaneous communication (Kouri, 1988). However, no effect size confidence intervals or p value data were provided. Effect sizes from a comparative study (Cardon & Wilcox, 2011) of reciprocal imitation and video modeling were in the medium range (NAP = 0.71–0.85) with the exception of one finding for video modeling which was large (NAP = 0.98); no p values or effect size confidence intervals were reported. Maintenance and generalization findings were quite variable among the studies that reported those data (Cardon, 2012; Cardon & Wilcox, 2011; Ingersoll & Schreibman, 2006).

In regard to group studies, the Brief Early Start Denver Model had a negligible post-treatment effect (d = −0.14) that was associated with a confidence interval that contained the null effect (Rogers et al., 2012). Maintenance findings, provided in a study of Hanen’s More than Words® (Carter et al., 2011), were negligible (i.e., d = 0) and accompanied by a confidence interval that contained the null effect. No generalization findings were reported.

Emerging language–language and related cognitive skills findings

The majority of studies (n = 18) examined interventions that addressed emerging language–language and related cognitive skills (see Table 4 for a list of interventions and associated outcomes). Findings from single-subject studies were in the small to large magnitude range (NAP = 0–1.00), with effect sizes from the following studies falling in the medium to large range: developmental, social pragmatic intervention (Ingersoll, Dvortcsak, Whalen, & Sikora, 2005); treatment strategy intervention (Kashinath, Woods, & Goldstein, 2006); behavioral intervention (Williams, Pérez-González, & Vogt, 2003); and enhanced milieu teaching (Kaiser, Hancock, & Nietfeld, 2000). No p values or effect size confidence intervals were reported. Effect sizes from a comparative study (Jennett, Harris, & Delmolino, 2008) of discrete trial training and mand training were large (NAP = 0.94–1.00). In another comparative study (Schreibman, Stahmer, Cestone Barlett, & Dufek, 2009), effect sizes for the pivotal response training were medium to large (NAP = 0.47–0.97), whereas those for discrete trial training were small to medium (NAP = −0.28 to 0.59). No p values or effect size confidence intervals were reported in either comparative study. There was notable variability in maintenance and generalization findings in the four studies (Ingersoll et al., 2005; Ingersoll & Schreibman, 2006; Kaiser et al., 2000; Vernon et al., 2012) that reported those data.

The effect sizes from group studies spanned from small to large in magnitude (d = −0.24 to 0.66). Most findings were not statistically significant with the exception of some or all from the Autism 1-2-3 Project study (Wong & Kwan, 2010) and the Early Start Denver Model study (Dawson et al., 2010). Effect sizes from comparative studies of an eclectic intervention versus an applied behavioral analysis intervention (Zachor & Itzchak, 2010) and an interpersonal synchrony versus non-interpersonal synchrony intervention (Landa et al., 2011) were small to medium in magnitude and not statistically significant. All statistically significant within-group pre- to post-test gains as well as gain scores between groups were in favor of the intervention group (Landa et al., 2011). Growth rate effect size was small (d = 0.09) and not statistically significant (p = .83; Landa et al., 2011). Maintenance findings from a study of Hanen’s More than Words ®(Carter et al., 2011) were small to medium in magnitude (d = −0.16 to 0.42) and accompanied by confidence intervals that contained the null effect. In Landa and colleague’s (2011) comparative study, the maintenance effect size was medium in magnitude (d = 0.57) and accompanied by a non-statistically significant p value (p = .24), whereas the growth rate data collected during the maintenance period translated into a small effect size (d = 0.09) and non-statistically significant p value (p = .83). No generalization findings were reported.

Discussion

This review of 26 intervention studies including 427 toddlers with ASD and spanning across a broad range of intervention categories indicated primarily positive treatment effects on social communication skills in terms of both growth rates and gain scores for all outcome categories for which social communication data were available, with the exception of emerging language–language and related cognitive skills, which showed variable and mixed results. Maintenance results were also variable across all outcome categories and reporting of generalization results was limited. As a whole, caregivers were satisfied with the interventions and their associated outcomes.

The overall body of literature included in this review was of appropriate scientific rigor with 24 of the 26 studies sufficiently meeting the majority of the critical appraisal points. Yet, patterns of weakness in research design were noted for both single-subject design (e.g., assessors were not blind to treatment) and group studies (e.g., use of convenience sampling). Despite these areas of weakness, no distinct patterns were detected between study quality indicators and reporting of outcomes with the exception of the Kouri (1988) study. Although the Kouri study reported large effects for the three prelinguistic outcome areas, this study met only 4 of the 12 quality indicator appraisal items. Given potential weaknesses in the design of this particular study, it is possible that effect sizes for this study could be inflated and should be interpreted with caution. Following is a discussion of treatment effects on social communication within the context of study design.

Single-Subject Designs

Single-subject intervention studies targeting social communication outcomes for toddlers with ASD generally reported improvements across outcome categories. Medium to large effects were present for the bulk of studies reporting outcomes for the three prelinguistic outcome categories. For the joint attention outcomes, the largest variability in effects was reported for the interventions in the joint attention category. Variability in improvement was reported for the emerging language–language and related cognitive skills category as evidenced by effects that ranged from small to large. For the proportion of studies that reported maintenance and generalization findings, outcomes were highly variable.

Group Designs

The seven group design studies included in this review showed positive trends in growth with respect to social communication outcomes and a range of effect sizes were reported; however, very few results indicated statistical significance. In summarizing the social communication outcomes reported for group studies, the most promising effects appear to be in favor of clinician-implemented interventions providing the greatest intensity (Dawson et al., 2010; Landa et al., 2011). Schertz and colleagues (2013) provided the single exception to this by reporting on a parent-implemented intervention of brief duration and intensity having an effect on joint attention as well as an effect on emerging language and related cognitive skills in favor of the treatment group. Because this particular study, however, did not blind assessors to the treatment condition, the findings may be biased and must be viewed with caution.

Overarching Implications of Findings

Both focused interventions, which are directed toward improving targeted symptoms or needs of the child with ASD, and comprehensive interventions, which are developed to broadly reduce autism symptoms and improve overall functioning, have been used to improve social communication functioning in children with ASD. Single-subject design studies included in this review were typically associated with positive changes in social communication outcomes, whereas interventions assessed within-group studies mainly resulted in mixed findings. However, a summary of findings relative to our research questions across study designs indicates a preponderance of promising effects for prelinguistic-joint attention and social reciprocity outcomes, with the bulk of interventions associated with moderate to large treatment effects. With respect to language and related cognitive outcomes at both the prelinguistic and emerging language stages, an inconsistent picture emerges given the broad range of treatment effects reported. Finally, the studies reviewed provided no indication of effects on behavioral and emotional regulation outcomes. Although the positive results reported for social communication outcomes for toddlers with ASD are encouraging, the mixed nature of these results raises concerns with respect to the focus of treatment outcomes, treatment intensity, and agent of delivery (e.g., clinician versus parent-mediated), as well as the types of measures utilized to document intervention outcomes.

Focus of Treatment

The application of a developmental framework ensures that prelinguistic-social communication skills are addressed prior to symbolic language (ASHA, 2006; NRC, 2001; Prizant, Wetherby, Rubin, & Laurent, 2003). In stark contrast to that developmental emphasis is the finding that the majority of studies in this EBSR were focused on emerging language–language and related cognitive skills. With relatively few studies evaluating the effects of earlier-emerging, foundational social communication skills, such as joint attention and social reciprocity, we question whether normal developmental trajectories are being overlooked in the bulk of toddler interventions for ASD. Because longitudinal research has shown clearly the link between early social communication skills such as joint attention and long-term linguistic outcomes such as initiating bids and sharing emotions (Wetherby, Watt, Morgan, & Shumway, 2007) a stronger impetus for selecting outcome goals related to the core challenges of ASD seems warranted. Of additional concern is the fact that no studies reported behavior and emotional regulation findings. It may be that these collective skills have not been targeted due to challenges with measurement or other practical reasons.

Intensity

Although several systematic review panels have recommended active engagement in intensive instruction for a minimum of 5 hr per day (Maglione, Gans, Das, Timbie, & Kasari, 2012; NRC, 2001), none of the included studies in this review evaluated intensity of instruction to that extent. One study, however, did report an average of 20 hr per week (Dawson et al., 2010). Although the findings of this EBSR suggest that fewer hours of treatment may be sufficient to ameliorate social communication deficits and support growth in social communication skills, it is unclear what the critical mass is for maximizing long-term outcomes for children with ASD.

That the most promising effects on social communication outcomes appear to be in favor of clinician-implemented interventions providing the greatest intensity (Dawson et al., 2010; Landa et al., 2011), raises concerns for future research. First, it is important to determine whether comparable treatment effects can be achieved with reduced professional time since practical, sustainable application in community settings may be compromised due to limited access to and the high costs of qualified and trained professionals. Second, while current studies highlight potential limitations of parent-mediated approaches, these interventions have greater longevity given the number of hours a child spends with his or her parents versus clinicians both in these early stages and beyond (Woods & Brown, 2011). Thus, it is important to evaluate innovative ways to maximize dosage and intensity of parent-implemented interventions and to incorporate strategies for accurate measurement of the intensity with which parents implement intervention techniques during everyday activities.

Agent of Delivery and Setting

The majority of studies included in this review described delivery of treatment as a shared effort between the professional and the caregiver, with interventions being carried out in clinical, classroom, and home settings. Several studies did not clearly indicate these methodological details. Given that purely parent-implemented studies have not reported significant effects on child social communication outcomes, it is critical for parent-implemented interventions to be evaluated while controlling for density of parent implementation, including measures of treatment fidelity and evaluation of parent learning.

As a result of the documented challenges with generalization of learning for children with ASD, natural environments have been recommended as preferred intervention contexts. Because treatment provided by caregivers in a natural environment could be utilized to address issues related to dosage and intensity, future research should address the relative effects of providing intervention in natural versus more clinically oriented settings. Related to issues of context and whether caregivers or professionals are delivering the treatment is that new skill maintenance and generalization in natural contexts should be carefully evaluated. Only a handful of studies reported evaluating generalization and maintenance, and those findings were not assessed across a variety of contexts and/or communication partners, with the exception of the Krstovska-Guerrero and Jones (2013) study which evaluated generalization across communication partners (i.e., interventionist and caregiver) and with novel materials.

Measurement

The challenge of comparing results across study designs was further compounded by types of outcome measures administered. Proximal measures were typically used in single-subject designs to detect specific, incremental changes in target behaviors (e.g., frequency of parent–child interactions; Green et al., 2010) that directly correspond to what was addressed in treatment via direct observations, whereas distal measures, assessments used to ascertain the transfer of change from intervention targets, were often used in group designs (e.g., Vineland Adaptive Behavior Scales [VABS]; Sparrow, Cicchetti, & Balla, 2005). Differences in the degree of sensitivity of the two outcome measures varies depending on the type of outcome (i.e., proximal or distal) measured. In concert, these findings warrant more single-subject and group design studies that include a combination of proximal and distal measures of outcome.

Limitations of This EBSR

This EBSR has two primary limitations that are worthy of note. To ensure that experts in the field vetted study quality, only peer-reviewed research was accepted in this EBSR. However, since the likelihood of publishing studies with significant findings is higher than the likelihood of publishing studies with non-statistically significant results, the risk of publication bias is high. Only studies written in English were accepted, which limited the scope of the search for relevant articles for this EBSR. As is the case with only accepting peer-reviewed studies, studies on this topic written in other languages could provide another dimension to the understanding of this topic and/or may contain results that are principally contrary to the findings in this EBSR.

Conclusion

Although the mixed results described above prevent definitive statements about the efficacy of social communication interventions for the infant and toddler population with ASD, the positive findings from this review and previous reviews (e.g., NRC, 2001; Schertz et al., 2012) suggest benefit from interventions focusing on social communication. Limited research for this population is available with respect to some of the specific intervention domains identified as critical by the ASHA (2006) guideline that addresses diagnosis, assessment, and intervention of difficulties associated with ASD across the life span. As longitudinal research provides additional evidence as to long-term outcomes associated with acquisition of early social communication skills, a stronger emphasis on outcome goals related to the core challenges of ASD in prelinguistic-social communication may be revealed. Interventions that have the potential to be implemented by early intervention systems that address multiple outcomes and can provide a strong family component designed to maximize child active engagement are identified as critical priorities for the next phase of intervention research.

Footnotes

Authors’ Note

This systematic review was conducted under the auspices of the American Speech-Language-Hearing Association; however, this is not an official position statement of the Association.

Declaration of Conflicting Interests

The author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: Three of the authors are salaried employees of the American Speech-Language-Hearing Association, the organization through which this systematic review was completed.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Supplemental Material

Supplemental Materials Tables 1 –4 are available at .

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