Autism Spectrum Disorder, Language Disorder, and Social

Autism Spectrum Disorder, Language Disorder, and Social

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Autism Spectrum Disorder, Language Disorder, and Social

(Pragmatic) Communication Disorder: Overlaps,

Distinguishing Features, and Clinical Implications

Lauren J. Taylor1 and Andrew J. O. Whitehouse2

1

School of Psychology, University of Western Australia, and 2

Telethon Kids Institute, University of Western Australia

Background: The diagnostic boundaries between autism spectrum disorder (ASD) and specific language impairment (SLI) are not clear-cut.

Evidence of the lack of distinct boundaries between these disorders comes from research identifying a group of children who have pragmatic

language difficulties that can be distinguished from those in children with SLI and those with ASD. These findings have led to the inclusion of

a new diagnostic category, social (pragmatic) communication disorder (SPCD), in the Diagnostic and Statistical Manual of Mental Disorders5th Edition DSM-5. While this new diagnostic category appears to capture a subgroup of children who may not have been recognised in the

DSM-IV, SPCD has been criticised due to a lack of empirical evidence, showing that the disorder is distinct from ASD in terms of aetiology,

intervention, and prognosis.

Objective: The purpose of this paper was to summarise the literature that has investigated overlaps in the phenotypes of SLI, ASD, and

SPCD. A secondary objective was to present a framework for the assessment and diagnosis of these three conditions.

Method and Results: In this paper, we review the research that has examined overlaps in the aetiologies and phenotypes of ASD, SPCD,

and SLI. While the results highlighted overlaps in the language profiles and autistic symptomatology, these three conditions could also be distinguished based on the severity of the social communication deficits and the absence of rigid and repetitive behaviour in strictly defined

cases of SPCD and SLI.

Conclusions: Strictly defined cases of SPCD and SLI can be distinguished from ASD. However, there is a lack of assessment tools that can

reliably distinguish these three conditions. We consider the clinical implications of the findings and present a model of assessment and diagnosis for ASD, SLI, and SPCD.

Key words: assessment; autism; diagnosis; social communication disorder; specific language impairment.

What is already known about this topic?

1 The boundaries between autism spectrum disorder (ASD), specific language impairment (SLI), and social (pragmatic) communication disorder (SPCD) are not clear-cut.

2 While SPCD was included in the Diagnostic and Statistical Manual of Mental Disorders-5th Edition (DSM-5), it is unclear

whether this disorder is distinct from ASD.

3 Assessment and diagnosis of ASD, SLI, and SPCD is challenging

because there are no measures that can reliably distinguish

these three conditions.

What this topic adds

1 In this article, we summarise the evidence regarding overlap

between ASD, SLI, and SPCD in terms of aetiology, language,

autistic symptomatology, and long-term outcomes.

2 Strictly defined cases of SPCD can be distinguished from ASD

based on the severity of social communication deficits.

3 We present a framework for the assessment and diagnosis of

ASD, SLI, and SPCD.

The language phenotype of autism spectrum disorder (ASD) is

highly heterogeneous. While some individuals with ASD fail to

develop functional verbal communication, others have fluent

language skills, experiencing difficulties only with social communication. The pragmatic difficulties in ASD contrast with the

structural language impairments, that is, in phonology, morphology, and syntax, observed in individuals with specific

Correspondence: Lauren Taylor, School of Psychology, M304, University

of Western Australia, 35 Stirling Highway, Crawley, Western Australia

6009, Australia.

Email: lauren.taylor@uwa.edu.au

Accepted for publication 4 April 2016

doi:10.1111/ap.12222

Australian Psychologist 51 (2016) 287–295

© 2016 The Australian Psychological Society

287

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language impairment (SLI). A substantial body of empirical literature has been dedicated to understanding the phenomenology of SLI. However, this label has not previously been

included in the diagnostic nomenclature (see Rapin, 1996 for a

practitioner review of developmental language disorders).

Research studies have used a range of criteria to identify children with SLI, which is generally accepted to occur when children experience a clinically significant delay in language

development despite having adequate hearing, non-verbal

intelligence, and educational opportunities (Bishop, 2003c;

Stark & Tallal, 1981).1

While “textbook” cases of ASD and SLI can be readily distinguished, in clinical practice, the boundaries between these two

disorders are not clear-cut. Extensive evidence now indicates

that a subgroup of children with ASD has a language impairment that resembles SLI (Kjelgaard & Tager-Flusberg, 2001;

Lewis, Murdoch, & Woodyatt, 2007; Lloyd, Paintin, & Botting,

2006; Rapin & Dunn, 2003; Rapin, Dunn, Allen, Stevens, &

Fein, 2009). For example, in one important study, Kjelgaard

and Tager-Flusberg (2001) divided children with ASD into

“normal” (ALN; standard scores greater than 85), “borderline”

(standard scores between 70 and 84), and “impaired” (ALI;

standard scores less than 70) language groups based on their

scores on a series of standardised language assessments. The

ALI subgroup demonstrated poor performance on tests of phonological processing, vocabulary, and higher-order grammatical

and semantic skills, with deficits in these areas closely resembling the SLI phenotype. There is substantial empirical support

for these findings, with a language impairment specifier outlined in the most recent revision of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5). This specifier will

capture children who present with ASD and comorbid language impairment.

Further evidence for the lack of clear-cut boundaries

between ASD and SLI comes from studies that have identified

children with communication characteristics that are intermediate between “textbook” ASD and SLI. Substantial research

has provided an evidence base for a subgroup of children with

primary pragmatic language impairments (PLI) who can be distinguished from children with SLI and those with ASD

(Bishop & Norbury, 2002; Botting & Conti-Ramsden, 1999,

2003a, 2003b). The DSM-5 contains a new category of neurodevelopmental disorders, Social (pragmatic) communication

disorder (SPCD), which may capture children previously considered to have PLI.2 SPCD is identified when children demonstrate deficits in using verbal and non-verbal communication

for social purposes (American Psychiatric Association, 2013).

Key diagnostic features include difficulties using communication for social purposes, understanding verbal and non-verbal

conversational rules, and understanding social nuances. The

pragmatic difficulties that characterise SPCD are likely to

resemble the core communication deficits of ASD, which may

suggest that ASD and SPCD are variable manifestations of the

same disorder (Tanguay, 2011). The distinguishing feature,

though, is rigid, repetitive, and stereotyped behaviour and

restrictive interests (RRBIs), which must be absent in SPCD

diagnoses. While this new diagnostic category appears to capture a subgroup of children who may not have been recognised

in the DSM-IV, social communication disorder has been

criticised due to a lack of empirical evidence showing that the

disorder is distinct from ASD (Ozonoff, 2012; Skuse, 2012; Tanguay, 2011).

ASD, SLI, and SPCD: Genes, Behaviour,

and Longitudinal Outcomes

While extensive evidence has investigated aetiological and

behavioural overlaps between ASD and SLI, relatively less

attention has focused on SPCD. In this section, we review the

research that has investigated overlaps between ASD, SLI, and

SPCD at the genetic and behavioural levels.

Genes and the Familial Aggregation of Structural

and Pragmatic Language Deficits

While numerous twin studies have shown that both ASD and

SLI are highly heritable (Bailey et al., 1995; Bishop, North, &

Donlan, 1995; Constantino & Todd, 2003; Folstein & Rutter,

1977a, 1977b), no published literature has examined the heritability of SPCD, likely reflecting the recent addition of this label

to the diagnostic nomenclature. Evidence does exist to suggest

that structural and pragmatic language impairments aggregate

within families (Bernier, Gerdts, Munson, Dawson, & Estes,

2012; Bolton et al., 1994; Gerdts, Bernier, Dawson, & Estes,

2013; Landa et al., 1992; Pickles, St Clair, & Conti-Ramsden,

2013; Piven et al., 1997; Taylor et al., 2015; Whitehouse,

Barry, & Bishop, 2007). In addition, the results of early twin

(Dworzynski et al., 2007, 2008) and family (Bailey, Palferman,

Heavey, & Le Couteur, 1998; Folstein et al., 1999; Ruser et al.,

2007; Tomblin, Hafeman, & O’Brien, 2003) studies have

revealed overlaps in the language characteristics among parents

and siblings of children with ASD and those with SLI. For

example, there is an elevated rate of language and literacy

impairments in parents and siblings of ASD probands, and

some of these family members also demonstrate poor performance on tests of non-word and sentence repetition, heritable

markers for SLI (Bailey et al., 1998; Folstein et al., 1999; Lindgren, Folstein, Tomblin, & Tager-Flusberg, 2009; Ruser et al.,

2007). Results of more recent studies indicate that the heritable

phenotypes of ASD and SLI breed true in these families (Bolton

et al., 1994; Folstein & Rosen-Sheidley, 2001; Landa et al.,

1992; Lindgren et al., 2009; Pickles et al., 2013; Whitehouse

et al., 2007; Whitehouse, Coon, Miller, Salisbury, & Bishop,

2010). The results of a prospective, longitudinal study of infant

siblings of children with ASD also indicate that at 36 months,

high-risk siblings had worse pragmatic language skills than

low-risk siblings, with 35% of the high-risk group identified as

having PLI, relative to only 10% of the low-risk group (Miller

et al., 2014). However, this study was limited due to the indirect measures of pragmatic language (Language Use Inventory;

O’Neill, 2009) and the sample bias that may result in inflated

rates of pragmatic impairments in the high-risk siblings, who

may be vulnerable to social communication deficits due to the

family history of ASD. Nevertheless, these findings indicate that

pragmatic language impairments are highly heritable in ASD

and may also highlight possible relationships between ASD and

SPCD among families.

Autism, SLI, and social communication disorder L.J. Taylor and A.J.O. Whitehouse

288 Australian Psychologist 51 (2016) 287–295

© 2016 The Australian Psychological Society

The results of several studies have also revealed overlaps in

genes that may confer susceptibility to ASD, SLI, and social

communication deficits. A specific gene located on 7q35, Contactin Associated Protein-Like 2 (CNTNAP2), has attracted particular interest as polymorphisms in this region have been

identified in multiple-incidence ASD families (Alarcón et al.,

2008; Arking et al., 2008; Bakkaloglu et al., 2008). Vernes

et al. (2008) also found significant associations between polymorphisms on CNTNAP2 and impaired non-word repetition, a

heritable marker for SLI. Recent evidence also indicates that

there may be associations between common genetic variants

related to ASD and semantic-pragmatic skills (St Pourcain

et al., 2013; Steer, Golding, & Bolton, 2010). These findings

indicate that there may be shared genetic influences on ASD

and social communication skills.

Psycholinguistic Markers of SLI

Putative behavioural markers for SLI include impaired nonword repetition, poor oromotor skills (Barry, Yasin, & Bishop,

2007), and deficits in the acquisition and use of tense-marking

morphemes (Rice & Wexler, 1996; Tager-Flusberg & Joseph,

2003). Considerable research in this area has focused on nonword repetition tasks, which are purported to test phonological

short-term memory. In this task, children hear nonsense words

of increasing length and complexity and repeat them verbatim.

Extensive evidence indicates that children with SLI demonstrate poor performance on non-word repetition tasks, thought

to index phonological short-term memory, a core cognitive deficit in this population (Gathercole & Baddeley, 1990). Extensive

evidence indicates that a subgroup of children with ASD who

have comorbid language impairments demonstrate non-word

repetition performance that resembles children with SLI

(Kjelgaard & Tager-Flusberg, 2001; Lindgren et al., 2009; Loucas et al., 2010; Riches, Loucas, Baird, Charman, & Simonoff,

2011; Tager-Flusberg, 1996, 2006; Whitehouse, Barry, &

Bishop, 2008), highlighting overlaps in the language phenotypes of these two groups. However, the groups can be distinguished based on the error patterns as children with SLI make

more errors than children with ASD on long (four-syllable) relative to short (two-syllable) non-words (Riches et al., 2011;

Whitehouse et al., 2008). These findings indicate that the cognitive origin of the non-word repetition deficits may differ

between the two conditions.

Findings regarding children with PLI have been less conclusive. Botting and Conti-Ramsden (2003a, 2003b) explored

whether performance on non-word repetition, sentence repetition, and past tense-marking tasks could be used to distinguish

ASD, PLI, and SLI. While the scores for the ASD and SLI groups

were uniform, scores for the PLI group were highly variable.

Therefore, the author divided this group into two subgroups:

“PLI pure,” that is, children with pragmatic impairments only,

and “PLI plus,” those with pragmatic impairments as well as

restricted social behaviour and/or interests. This division

resulted in significant differences across the four groups. While

the SLI groups could be distinguished from the ASD, PLI Pure,

and PLI Plus groups based on poor non-word repetition performance, the latter three groups could not be differentiated on

this task. In contrast, the SLI, PLI Pure, and ASD groups were

all impaired on the past tense-marking and sentence repetition

tasks and could not be distinguished on either of these measures. The PLI Plus group had significantly higher scores than

the SLI, PLI Pure, and ASD groups on the tense-marking task

and the SLI and PLI Pure groups on the sentence repetition

task. Sensitivity and specificity analysis revealed that the sentence repetition task was the most accurate marker, distinguishing all but the PLI Plus group from typically developing

peers. Therefore, while psycholinguistic markers can accurately

distinguish children with communication disorders from their

typically developing peers, these markers alone cannot reliably

discriminate ASD from SLI or from PLI.

ASD Symptomatology

RUBRIC
Excellent Quality 95-100%	Introduction 45-41 points The background and significance of the problem and a clear statement of the research purpose is provided. The search history is mentioned.		Literature Support 91-84  points The background and significance of the problem and a clear statement of the research purpose is provided. The search history is mentioned.			Methodology 58-53 points Content is well-organized with headings for each slide and bulleted lists to group related material as needed. Use of font, color, graphics, effects, etc. to enhance readability and presentation content is excellent. Length requirements of 10 slides/pages or less is met.
Average Score 50-85%	40-38 points More depth/detail for the background and significance is needed, or the research detail is not clear. No search history information is provided.		83-76  points Review of relevant theoretical literature is evident, but there is little integration of studies into concepts related to problem. Review is partially focused and organized. Supporting and opposing research are included. Summary of information presented is included. Conclusion may not contain a biblical integration.			52-49  points Content is somewhat organized, but no structure is apparent. The use of font, color, graphics, effects, etc. is occasionally detracting to the presentation content. Length requirements may not be met.
Poor Quality 0-45%	37-1 points The background and/or significance are missing. No search history information is provided.		75-1 points Review of relevant theoretical literature is evident, but there is no integration of studies into concepts related to problem. Review is partially focused and organized. Supporting and opposing research are not included in the summary of information presented. Conclusion does not contain a biblical integration.			48-1 points There is no clear or logical organizational structure. No logical sequence is apparent. The use of font, color, graphics, effects etc. is often detracting to the presentation content. Length requirements may not be met
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