Specifying PDD-NOS: a comparison of PDD-NOS, Asperger syndrome, and autism

OBJECTIVE: To describe the clinical characteristics of children given a diagnosis of pervasive developmental disorder-not otherwise specified (PDD-NOS) by expert clinicians and to compare these to the clinical characteristics of children given a diagnosis of autism and Asperger syndrome (AS). METHOD: Two hundred sixteen children with autism, 33 with AS, and 21 with PDD-NOS were compared on measures of level of functioning (communication, daily living and social skills, IQ, and age of acquisition of language) and on various symptoms of autism (impaired communication and reciprocal social interaction and a preference for repetitive and stereotyped activities). RESULTS: In terms of level of functioning measures, the PDD-NOS children had scores that were between those of the children with autism and those of the children with AS. In contrast, the PDD-NOS group had fewer autistic symptoms, especially repetitive stereotyped behaviors, than both the autism and AS groups (chi2 = 11.06, p =.004). Children with PDD-NOS could be placed into one of three subgroups: a high-functioning group (24%) who resembled AS but had transient language delay or mild cognitive impairment; a subgroup resembling autism (24%) but who had late age of onset or too severe cognitive delays or were too young to potentially meet the full diagnostic criteria for autism; and a group (52%) not fulfilling the criteria for autism because of fewer stereotyped and repetitive behaviors. CONCLUSIONS: With some revision to current diagnostic criteria, a more homogenous atypical group with significant impairments in social-communication but fewer repetitive behaviors can be differentiated from the more nonspecific PDD-NOS group. This differentiation may lead to better reliability in diagnosis and to further progress in studies of etiology.     

Current trends in psychological research on children with high-functioning autism and Asperger disorder

PURPOSE OF REVIEW: This review explores current trends in the literature during 2004 on psychological studies of children with high-functioning autism and Asperger syndrome. Studies are reviewed that examine diagnostic dilemmas and methodological concerns, cognitive and social deficits, and interventions. RECENT FINDINGS: There is considerable debate over the distinction between high-functioning autism and Asperger syndrome, but few studies find support for separate disorders. Most studies reviewed combine high-functioning autism and Asperger syndrome into an autism spectrum disorder group or study only one diagnostic group, either high-functioning autism or Asperger syndrome. Research into cognitive processes (specifically mentalizing) and social understanding (nonliteral language) continue to dominate research efforts. Current studies suggest specific weaknesses in many areas of nonliteral language, such as humor, irony, and teasing. Studies rely heavily on current theoretical explanations for deficits, namely the central coherence, social inference, and executive function theories, and varying levels of support were found for all three theories. Intervention and outcome studies lag behind experimental and theoretical studies, but two studies employed scientifically rigorous intervention designs with promising results. SUMMARY: Children with high-functioning autism and Asperger syndrome have a great deal of potential with respect to long-term developmental outcomes, and yet they continue to be understudied and under-served in current intervention programs. Future studies are needed in developmental processes and outcomes in this population, and in the development of effective treatment strategies that have undergone scientifically rigorous testing.     

Obstetric factors in Asperger syndrome: comparison with high-functioning autism

Asperger syndrome (AS) is a pervasive developmental disorder widely regarded as a mild variant of autism. To investigate if AS is associated with a history of fewer obstetric insults compared to autism, we examined the developmental history and obstetric records of 10 males with AS (mean full scale IQ 95.3), and compared them with 10 autistic males with a full scale IQ of 70 or above (so-called high-functioning autism; mean full scale IQ 82.6). Males with AS showed a trend toward lower Apgar scores at one minute (chi-square=4; df=l; P=0.04) and were more likely to have been born to mothers outside the optimal age group of 20–30 years (chi-square=5; df= 1; P=0.02). They were also less likely to have been irritable and floppy as infants (chi-square=3.8; df= I; P=0.05). However, the total optimality scores did not differ significantly between the two groups.     

The Strange Stories Test: A Replication with High-Functioning Adults with Autism or Asperger Syndrome

Two groups of individuals, one with high-functioning autism and the other with Asperger syndrome were tested using Happé's Strange Stories Test of a more advanced theory of mind (Happé, 1994). This assesses the ability to interpret a nonliteral statement. Relative to normal controls who were IQ and age-matched, individuals with autism or Asperger syndrome performed less well on the task, while performing normally on a non-mentalistic control task. Individuals with autism or Asperger syndrome could provide mental state answers, but had difficulty in providing contextually appropriate mental state answers. Rather, their answers tended to concentrate on the utterance in isolation. This replicates Happé's result. Although the majority of both clinical groups provided context-inappropriate interpretations, the autism group had the greater difficulty. Results are discussed in relation to both weak central coherence and theory of mind.     

The effect of selection criteria on outcome studies of children with pervasive developmental disorders (PDD)

The objective of this paper is to see whether regression to the mean biases the differences on outcome observed between children with Asperger syndrome and autism. Children with pervasive developmental disorders (PDD) and normal nonverbal IQ were divided into those with Asperger syndrome and autism. It was hypothesized that IQ in the autistic children would fall at the 2-year outcome assessments since the autistic group represented a subgroup selected on the basis of extreme scores on a single measure. In fact, the Asperger syndrome group experienced a significant drop in nonverbal IQ contrary to expectation. Serial measurements of non-verbal IQ at inception indicated that this drop was probably a function of high initial nonverbal IQ scores that fall over time due to increasing complexity of problem-solving tests. The results are discussed in relation to outcome studies of high functioning children with PDD.     

Residual Difficulties with Categorical Induction in Children with a History of Autism

In two experiments, typically developing (TD) children, high-functioning children with autism (HFA) and children with a history of autism who have achieved optimal outcomes (OOs), matched on age (M = 13 years) and nonverbal IQ, were asked to extend properties of categories to new items (categorical induction). All groups demonstrated some knowledge of category structure by extending at above-chance levels; however, the TD group extended more consistently than the OO and HFA groups. More consistent extenders had higher lexical and nonverbal IQ scores (Experiment 1) or higher pragmatics scores (Experiment 2). Thus, even very high functioning individuals with autism, or with an OO, still exhibit residual difficulties with category knowledge and extension; moreover, category tasks relate to a variety of verbal and nonverbal abilities. The difficulty these groups had with categorical induction may be related to their difficulty with generalization more widely; future research should investigate this possibility.     

Profiles of receptive and expressive language abilities in boys with comorbid fragile X syndrome and autism

Abstract The authors examined receptive and expressive language profiles for a group of verbal male children and adolescents who had fragile X syndrome along with varying degrees of autism symptoms. A categorical approach for assigning autism diagnostic classification, based on the combined use of the Autism Diagnostic Interview-Revised and the Autism Diagnostic Observation Schedule (ADOS), and a continuous approach for representing autism symptom severity, based on ADOS severity scores, were used in 2 separate sets of analyses. All analyses controlled for nonverbal IQ and chronological age. Nonverbal IQ accounted for significant variance in all language outcomes with large effect sizes. Results of the categorical analyses failed to reveal an effect of diagnostic group (fragile X syndrome-autism, fragile X syndrome-no autism) on standardized language test performance. Results of the continuous analyses revealed a negative relationship between autism symptom severity and all of the standardized language measures. Implications for representing autism symptoms in fragile X syndrome research are considered.     

Language and ToM development in autism versus Asperger syndrome: Contrasting influences of syntactic versus lexical/semantic maturity

Theory of mind (ToM) development by a sample of 63 children aged 5–12 years (24 with Asperger syndrome, 19 with high-functioning autism, and 20 age-matched typical developers) was assessed with a five-task false-belief battery in relation to both lexical (vocabulary) and syntactic (grammar) language skills. Contrary to some previous research, no differences in ToM emerged between those with Asperger syndrome and their typically developing peers but those with autism were delayed substantially behind both other groups in ToM understanding, even after controlling for age, non-verbal ability and verbal (both lexical and syntactic) mental age. For all the diagnostic groups equally, syntax was a more important ToM predictor than lexical language skill. Theoretical and practical implications of the findings are discussed.     

Electrophysiological signs of supplementary-motor-area deficits in high-functioning autism but not Asperger syndrome: an examination of internally cued movement-related potentials

Aims  Motor dysfunction is common to both autism and Asperger syndrome, but the underlying neurophysiological impairments are unclear. Neurophysiological examinations of motor dysfunction can provide information about likely sites of functional impairment and can contribute to the debate about whether autism and Asperger syndrome are variants of the same disorder or fundamentally distinct neurodevelopmental conditions. We investigated the neurophysiology of internally determined motor activity in autism and Asperger syndrome via examination of movement-related potentials (MRPs).
Method  We used electroencephalography to investigate MRPs, via an internally cued movement paradigm, in the following three groups: (1) individuals with high-functioning autism (14 males, one female; mean age 13y 1mo, SD 4y 2mo, range 7y 8mo to 20y 9mo; mean Full-scale IQ 93.40, SD 20.72); (2) individuals with Asperger syndrome (10 males, two females; mean age 13y 7mo, SD 3y 9mo, range 8y 11mo to 20y 4mo; mean Full-scale IQ 103.25, SD 19.37), and (3) a healthy control group (13 males, seven females; mean age 14y 0mo, SD 3y 11mo; range 8y 4mo to 21y 0mo; mean Full-scale IQ 114.25, SD 11.29).
Results  Abnormal MRPs can reflect disruption of motor-related neural networks involving the basal ganglia, thalamus, and supplementary motor area. There was evidence for abnormal MRPs in autism (e.g. increased post-movement cortical activity, abnormal peak time) but not in Asperger syndrome.
Interpretation  The results support basal ganglia, thalamus, and supplementary motor area involvement as a likely source of motor dysfunction in autism, and provide further evidence for the neurobiological separateness of autism and Asperger syndrome.     

Do individuals with high functioning autism have the IQ profile associated with nonverbal learning disability?

Previously researchers have noted a high level of occurrence of the IQ profile associated with nonverbal learning disability (NLD) in Asperger syndrome (ASP) but not in high functioning autism (HFA). We examined the IQ profile scores of a large sample of children (n = 69) and adults (n = 77) with HFA, stringently diagnosed according to ADOS, ADI-R, and DSM-IV criteria, and a corresponding sample of typical child (n = 72) and adult controls (n = 107). At least one of the three primary components of the Wechsler pattern seen in NLD were found in 17–26% of the children and 20–32% of the adults with HFA. All three components occurred in slightly more than 5% of the children and adults with autism. Overall, the VIQ > PIQ profile seen in NLD occurred in 18% of the sample of individuals stringently diagnosed with HFA. Therefore, obtaining this IQ profile is not a valid clinical discriminator between NLD and HFA.     

Birth Order Effects on Nonverbal IQ Scores in Autism Multiplex Families

Lord (1992) published a brief report showing a trend for decreasing nonverbal IQ scores with increasing birth order in a sample of 16 autism multiplex families, and urged replication in a larger sample. In this report, analyses of nonverbal IQ scores for a sample of 144 autism multiplex families indicated that nonverbal IQ scores were significantly lower in secondborn compared with firstborn siblings with autism. This birth order effect was independent of gender as well as the age differences within sib pairs. No such birth order effects were found for social or communicative deficits as measured by the Autism Diagnostic Interview-Revised (ADI-R), but there was a modest tendency for increased scores for ritualistic behaviors for the firstborn sibs. Further, there were no gender differences on nonverbal IQ scores in this sample. Results are discussed in terms of implications for genetic studies of autism.     

Cognitive and symptom profiles in Asperger's syndrome and high-functioning autism

Asperger syndrome (AS) and autistic disorder are two subtypes of pervasive developmental disorders (PDD), but there has been considerable debate over whether AS and autistic disorder without mental retardation (IQ > or = 70), called high-functioning autism (HFA), are distinct conditions or not. The aim of the present paper was to clarify this issue through a comparison of cognitive function and autistic symptom profiles. Based on the DSM-IV and ICD-10 definitions of language acquisition, 36 age- and IQ-balanced subjects with AS (mean age, 12.8 years; mean full-scale IQ, 98.3) were compared with 37 subjects with HFA (mean age, 12.6 years; mean full-scale IQ, 94.6) on the Japanese version of the Wechsler Intelligence Scales and the Childhood Autism Rating Scale-Tokyo Version (CARS-TV). Compared with the HFA subjects, the AS subjects scored significantly higher on Verbal IQ, Vocabulary, and Comprehension, but scored significantly lower on Coding. Although the total CARS-TV score did not differ significantly between the two groups, AS subjects scored significantly lower (i.e. less abnormal) on Verbal communication and Non-verbal communication than did the HFA subjects. A history of normal language acquisition in early childhood could predict his/her better verbal ability in mid-childhood or later. Autistic cognitive characteristics shared by both AS and HFA subjects appear to support the validity of the current diagnostic classification of PDD.     

Defining the Intellectual Profile of Asperger Syndrome: Comparison with High-Functioning Autism

Asperger syndrome (AS) is a disorder of early childhood characterized by autistic social deficits, subtle communication impairment, and excessive isolated interests. There is no history of language delay or of mental retardation. Despite its increasing popularity as a distinct condition, its diagnostic validity remains uncertain. It is still unclear to what extent AS differs from autism with normal intelligence sometimes referred to as high-functioning autism (HFA). However, some reports have suggested that persons with AS possess a distinct profile on tests of intelligence characterized by a high verbal IQ and a low performance IQ, whereas in most cases with HFA, the pattern is reversed. Since few studies have directly compared AS subjects with HFA controls using unmodified diagnostic criteria and standardized measures of assessment, in this report we compared 22 AS subjects with 12 HFA controls, matched on age, sex and level of intelligence. As a group, subjects with AS showed a higher verbal IQ and higher scores on information and vocabulary subtests than those with HFA. However, scores of several AS and HFA subjects showed a mixed pattern. Implications of these findings are discussed in the context of the validity of Asperger Syndrome.     

Linguistic characteristics of individuals with high functioning autism and Asperger syndrome

This study examined the linguistic characteristics of high functioning individuals with autism and Asperger syndrome. Each group consisted of 10 participants who were matched on sex, chronological age, and intelligence scores. Participants generated a narrative after watching a brief video segment of the Social Attribution Task video. Each participant was then asked 10 questions related to the stimulus video. The narrative samples and responses to the questions were analysed linguistically. Individuals with high functioning autism and Asperger syndrome performed similarly on most measures of language function; however, results suggest there may be pragmatically‐based differences between the groups in the use of verb tense markers.     

Linguistic characteristics of individuals with high functioning autism and Asperger syndrome

This study examined the linguistic characteristics of high functioning individuals with autism and Asperger syndrome. Each group consisted of 10 participants who were matched on sex, chronological age, and intelligence scores. Participants generated a narrative after watching a brief video segment of the Social Attribution Task video. Each participant was then asked 10 questions related to the stimulus video. The narrative samples and responses to the questions were analysed linguistically. Individuals with high functioning autism and Asperger syndrome performed similarly on most measures of language function; however, results suggest there may be pragmatically-based differences between the groups in the use of verb tense markers.     

The diagnosis of autism and Asperger syndrome: findings from a survey of 770 families

As part of a wider survey of parents of children with autistic spectrum disorders in the UK, the diagnostic experiences of 614 parents of children with autism and 156 with Asperger syndrome were compared. Although the ages of the children in the two groups were very similar at the time of the survey, parents of children given a diagnosis of Asperger syndrome had experienced significantly longer delays and greater frustration in obtaining a diagnosis than those with a child with autism. In the 'autism group' the average age when diagnosis was confirmed was around 5.5 years; in the 'Asperger group' it was 11 years. Parents of children with a diagnosis of autism were generally aware of problems in their child's development by 18 months of age; in the Asperger group concerns emerged later, at around 30 months of age. Initial worries in both groups centred around abnormal social development but parents of children with Asperger syndrome were less likely to have noted communication problems. Stereotyped or repetitive behaviours were not prominent in the early years in either group. Despite the problems inherent in data collected by postal survey, many of the findings of this study are supported by other research. The practical implications of delayed diagnosis, especially in the case of more able children with Asperger syndrome are discussed.     

Pre- and perinatal factors in high-functioning females and males with autism

Pregnancy and delivery complications as indicated in medical records and maternal reports for 23 high-functioning autistic females and 23 high-functioning males of similar IQ and age were compared with those of 54 of their normally developing siblings. Autistic subjects of both sexes had higher non-optimality scores than their siblings. Much of this difference was accounted for by a higher incidence of firstborns and fourth- or later-borns in the autistic group. Of factors found in previous research with mentally handicapped, autistic samples, only estimated weeks of gestation greater than 42 occurred more often in autistic subjects than siblings. The only sex difference specific to the autistic group was that autistic males came from larger families than females. These data provide slight support for the contribution of nonspecific pre- and perinatal factors to other etiological bases of autism. It is proposed that pre- and perinatal factors may play less of a role in autism in high-functioning individuals than suggested in studies of autism associated with severe retardation.     

Predictors and Correlates of Adaptive Functioning in Children with Developmental Disorders

Autism is a developmental disorder marked by impairments in socialization, communication, and perseverative behavior and is associated with cognitive impairment and deficits in adaptive functioning. Research has consistently demonstrated that children with autism have deficits in adaptive functioning more severe than their cognitive deficits. This study investigates the correlates and predictors of adaptive functioning as measured by the Vineland Adaptive Behavior Scales in high- and low-functioning children with autism and their age and nonverbal IQ matched controls. Thirty-five 9-year-old children with high-functioning autism (HAD) were compared with 31 age-matched children with developmental language disorder (DLD), and 40 9-year-old children with low-functioning autism (LAD) were compared with 17 age-matched children with low IQ on adaptive functioning, IQ, autistic symptomology, and tests of language and verbal memory. Results indicate that both groups with autism were significantly impaired compared to their matched controls on Socialization and Daily Living, but not Communication and that these impairments were more pronounced in the HAD group than in the LAD group. Adaptive behavior was strongly correlated with autistic symptomology only in the HAD group. Regression analyses indicated that IQ was strongly predictive of adaptive behavior in both low-functioning groups, but tests of language and verbal memory predicted adaptive behavior in the higher functioning groups. Results suggest that IQ may act as a limiting factor for lower functioning children but higher functioning children are impaired by specific deficits, including autistic symptomology and impaired language and verbal memory.     

The long-term course of autistic disorders: update on follow-up studies

The majority of children with autism show deviance and socially or psychiatrically handicapping conditions throughout life. Only a small proportion of those with classical childhood autism lead independent adult lives. Others, particularly those with ‘high-functioning’ autism and so-called Asperger syndrome will improve enough to live an independent adult life. The level of mental retardation and other comorbid conditions (such as medical syndromes and other neuropsychiatric disorders, including epilepsy) is important in predicting outcome. An IQ below 50 around school age predicts severe restriction of social and adaptive functioning in adult life. The absence of communicative speech at 5–6 years of age is indicative of a poorer long-term overall outcome. There is a clear co-variation between IQ and level of communication, but probably there is some prognostic factor in language development apart from this. Measures of flexibility and cognitive shifting abilities tend to be good predictors of social outcome in a few studies. There is a continued need for prospective, longitudinal studies of children with autism spectrum disorders, particularly in Asperger syndrome. The role of interventions of various kinds needs to be addressed in such studies.     

The effects of intellectual functioning and autism severity on outcome of early behavioral intervention for children with autism

This study assessed the relation between pre-intervention variables (cognition, socialization and communication) to outcome in young children with autism. METHOD: Twenty five children with autism (20-32 months) were enrolled in intensive behavior intervention. The children were divided into groups based on their IQ scores and on the severity of their social interaction and communication deficits [per autism diagnostic observation schedule (ADOS) scores]. Six developmental-behavioral domains including, imitation, receptive language, expressive language, nonverbal communication skills, play skills and stereotyped behaviors were assessed at pre- and post-1 year of intervention times. RESULTS: Significant progress was noted in all the six developmental-behavioral domains after 1 year of intervention. Children with higher initial cognitive levels and children with fewer measured early social interaction deficits showed better acquisition of skills in three developmental areas, receptive language, expressive language and play skills. Both groups showed better progress in Receptive language skills. Better progress in expressive language was associated with the child's social abilities, while more significant progress in play skills was related to pre-intervention cognitive level. CONCLUSIONS: These findings emphasize the importance of early intensive intervention in autism and the value of pre-intervention cognitive and social interaction levels for predicting outcome.