Gillian Baird

Prevalence of disorders of the autism spectrum in a population cohort of children in South Thames: the Special Needs and Autism Project (SNAP)

BACKGROUND Recent reports have suggested that the prevalence of autism and related spectrum disorders (ASDs) is substantially higher than previously recognised. We sought to quantify prevalence of ASDs in children in South Thames, UK. METHODS Within a total population cohort of 56 946 children aged 9-10 years, we screened all those with a current clinical diagnosis of ASD (n=255) or those judged to be at risk for being an undetected case (n=1515). A stratified subsample (n=255) received a comprehensive diagnostic assessment, including standardised clinical observation, and parent interview assessments of autistic symptoms, language, and intelligence quotient (IQ). Clinical consensus diagnoses of childhood autism and other ASDs were derived. We used a sample weighting procedure to estimate prevalence. FINDINGS The prevalence of childhood autism was 38.9 per 10,000 (95% CI 29.9-47.8) and that of other ASDs was 77.2 per 10,000 (52.1-102.3), making the total prevalence of all ASDs 116.1 per 10,000 (90.4-141.8). A narrower definition of childhood autism, which combined clinical consensus with instrument criteria for past and current presentation, provided a prevalence of 24.8 per 10,000 (17.6-32.0). The rate of previous local identification was lowest for children of less educated parents. INTERPRETATION Prevalence of autism and related ASDs is substantially greater than previously recognised. Whether the increase is due to better ascertainment, broadening diagnostic criteria, or increased incidence is unclear. Services in health, education, and social care will need to recognise the needs of children with some form of ASD, who constitute 1% of the child population.

Infants with Autism: An Investigation of Empathy, Pretend Play, Joint Attention, and Imitation.

Systematic studies of infants with autism have not been previously carried out. Taking advantage of a new prospective screening instrument for autism in infancy (S. Baron-Cohen et al., 1996), the present study found that, compared with developmentally delayed and normally developing children, 20-month-old children with autism were specifically impaired on some aspects of empathy, joint attention, and imitation. Infants with autism failed to use social gaze in the empathy and joint attention tasks. Both the infants with autism and the infants with developmental delay demonstrated functional play, but very few participants in either group produced spontaneous pretend play. In the developmental delay group, but not the autism group, pretend play was shown following prompting. The implications of these findings for developmental accounts of autism and for the early diagnosis of the disorder are discussed.

A screening instrument for autism at 18 months of age: a 6-year follow-up study

OBJECTIVES A population of 16,235 children aged 18 months was screened using the Checklist for Autism in Toddlers (CHAT) to identify childhood autism (CA). Two further screening procedures were conducted at age 3 and 5 years. The population was followed up at age 7 years in order to establish the sensitivity, specificity, and positive predictive value of the instrument. METHOD A brief checklist assessing joint attention and pretend play behaviors was administered by primary health care practitioners when the children were 18 months old. Follow-up methods included screening through parents and health practitioners and checking medical and educational records. RESULTS Nineteen cases of CA were successfully identified by the CHAT at 18 months. At follow-up a total of 50 cases of CA were identified via all surveillance methods. Thus, the CHAT has a sensitivity of 38% and a specificity of 98% for identifying CA. The positive predictive value of the instrument was maximized by concentration on the highest-risk group. Repeated screening 1 month later increased the positive predictive value to 75% for identification of CA but reduced the sensitivity to 20%, although the specificity was close to 100%. The screen also identified cases of pervasive developmental disorder as well as children with language and other developmental disorders. CONCLUSIONS The CHAT can be used to identify cases of autism and related pervasive developmental disorders at 18 months of age. It is emphasized that the CHAT is not a diagnostic instrument but can identify potential cases of autism spectrum disorders for a full diagnostic assessment.

A genomewide screen for autism: Strong evidence for linkage to chromosomes 2q, 7q, and 16p

Autism is characterized by impairments in reciprocal communication and social interaction and by repetitive and stereotyped patterns of activities and interests. Evidence for a strong underlying genetic predisposition comes from twin and family studies, although susceptibility genes have not yet been identified. A whole-genome screen for linkage, using 83 sib pairs with autism, has been completed, and 119 markers have been genotyped in 13 candidate regions in a further 69 sib pairs. The addition of new families and markers provides further support for previous reports of linkages on chromosomes 7q and 16p. Two new regions of linkage have also been identified on chromosomes 2q and 17q. The most significant finding was a multipoint maximum LOD score (MLS) of 3.74 at marker D2S2188 on chromosome 2; this MLS increased to 4.80 when only sib pairs fulfilling strict diagnostic criteria were included. The susceptibility region on chromosome 7 was the next most significant, generating a multipoint MLS of 3.20 at marker D7S477. Chromosome 16 generated a multipoint MLS of 2.93 at D16S3102, whereas chromosome 17 generated a multipoint MLS of 2.34 at HTTINT2. With the addition of new families, there was no increased allele sharing at a number of other loci originally showing some evidence of linkage. These results support the continuing collection of multiplex sib-pair families to identify autism-susceptibility genes.

Autism Spectrum Disorders at 20 and 42 Months of Age: Stability of Clinical and ADI‐R Diagnosis

The association between, and stability of, clinical diagnosis and diagnosis derived from the Autism Diagnostic Interview-Revised (ADI-R; Lord, Rutter, & Le Couteur, 1994) was examined in a sample of prospectively identified children with childhood autism and other pervasive developmental disorders assessed at the age of 20 months and 42 months. Clinical diagnosis of autism was stable, with all children diagnosed with childhood autism at age 20 months receiving a diagnosis of childhood autism or a related pervasive developmental disorder (PDD) at age 42 months. Clinical diagnosis of childhood autism was also reasonably sensitive, with all children who went on to receive a clinical diagnosis of childhood autism at 42 months being identified as having autism or PDD at 20 months. However, clinical diagnosis for PDD and Aspergers syndrome lacked sensitivity at 20 months, with several children who subsequently received these diagnoses at 42 months receiving diagnoses of language disorder or general developmental delay, as well as in two cases being considered clinically normal, at the earlier timepoint. The ADI-R was found to have good specificity but poor sensitivity at detecting childhood autism at 20 months; however, the stability of diagnosis from 20 to 42 months was good. In addition, the ADI-R at age 20 months was not sensitive to the detection of related PDDs or Aspergers syndrome. The continuity and discontinuity between behavioural abnormalities identified at both timepoints in the three domains of impairment in autism was examined, both in children who met final clinical criteria for an autistic spectrum disorder, and for children with language disorder who did not, as well as for a small sample of typically developing children.

Testing joint attention, imitation, and play as infancy precursors to language and theory of mind

Abstract Various theoretical accounts propose that an important developmental relation exists between joint attention, play, and imitation abilities, and later theory of mind ability. However, very little direct empirical evidence supports these claims for putative “precursor” theory of mind status. A small sample ( N =13) of infants, for whom measures of play, joint attention, and imitation had been collected at 20 months of age, was followed-up longitudinally at 44 months and a battery of theory of mind measures was conducted. Language and IQ were measured at both timepoints. Imitation ability at 20 months was longitudinally associated with expressive, but not receptive, language ability at 44 months. In contrast, only the joint attention behaviours of gaze switches between an adult and an active toy and looking to an adult during an ambiguous goal detection task at 20 months were longitudinally associated with theory of mind ability at 44 months. It is argued that joint attention, play, and imitation, and language and theory of mind, might form part of a shared social–communicative representational system in infancy that becomes increasingly specialised and differentiated as development progresses.

The Frequency and Distribution of Spontaneous Attention Shifts between Social and Nonsocial Stimuli in Autistic, Typically Developing, and Nonautistic Developmentally Delayed Infants

Spontaneous shifts of attention were observed in autistic, typically developing, and nonautistic developmentally delayed infants. Three types of attention shifting behaviour were observed; (1) between an object and another object, (2) between an object and a person, and (3) between a person and another person. The two control groups shifted attention more frequently between an object and a person than between an object and another object or between a person and another person. The infants with autism showed a different pattern, shifting attention between an object and another object more than any other type of shift. Furthermore, infants with autism showed fewer shifts of attention between an object and a person, and between person and person, than did the two control groups. They also spent less time overall looking at people and looked more briefly at people and for longer durations at objects, compared to the two control groups. These results indicate an abnormality in social orientation in autism even at the early age of 20 months.

Impairment in movement skills of children with autistic spectrum disorders

Aim  We undertook this study to explore the degree of impairment in movement skills in children with autistic spectrum disorders (ASD) and a wide IQ range.

A pilot randomised control trial of a parent training intervention for pre-school children with autism: Preliminary findings and methodological challenges

Abstract. Few attempts have been made to conduct randomised control trials (RCTs) of interventions for pre-school children with autism. We report findings of a pilot RCT for a parent training intervention with a focus on the development of joint attention skills and joint action routines. Twenty-four children meeting ICD-10 criteria for childhood autism (mean age = 23 months) were identified using the CHAT screen and randomised to the parent training group or to local services only. A follow-up was conducted 12 months later (mean age = 35 months). There was some evidence that the parent training group made more progress in language development than the local services group. However, the present pilot study was compromised by several factors: a reliance on parental report to measure language, non-matching of the groups on initial IQ, and a lack of systematic checking regarding the implementation of the parent training intervention. Furthermore, three parents in the local services group commenced intensive, home-based behavioural intervention during the course of the study. The difficulties encountered in the conduct of RCTs for pre-school children with autism are discussed. Methodological challenges and strategies for future well-designed RCTs for autism interventions are highlighted.

The severity and nature of motor impairment in Asperger's syndrome: a comparison with Specific Developmental Disorder of Motor Function

BACKGROUND The aims of this study were to measure objectively the extent and severity of motor impairment in children with Aspergers syndrome and to determine whether the motor difficulties experienced by such children differed in any way from those classified as having a Specific Developmental Disorder of Motor Function (SDD-MF). Criteria derived from ICD 10-R were used to identify 11 children with Aspergers syndrome and a matched group of 9 children with a Specific Developmental Disorder of Motor Function. Children in both groups were required to have a verbal IQ of 80 or greater on the WISC IIIR. METHOD The Autism Diagnostic Interview (Revised; Lord, Rutter, & LeCouteur, 1994) was used to identify features of AS in the first group and to exclude them in the latter. The Movement Assessment Battery for Children (Henderson & Sugden, 1992) provided a standardised test of motor impairment. A Gesture Test based on that by Cermak, Coster, and Drake (1980) was used to assess the childs ability to mime the use of familiar tools and to imitate meaningless sequences of movements. RESULTS All the children with Aspergers syndrome turned out to meet our criterion for a diagnosis of motor impairment, five of the six most severely motor impaired children in the whole study being from this group. Performance of the Asperger group was also slightly poorer on the Gesture Test. The profile of performance on each test was examined in detail but no evidence of group differences in the pattern of impairment was found. CONCLUSIONS This study is consistent with others suggesting a high prevalence of clumsiness in Aspergers syndrome. Our findings also attest to the widespread prevalence of motor impairment in developmental disorders and the problems such co-morbidity poses for attempts to posit discrete and functionally coherent impairments underlying distinct syndromes.