Classification of autism and related conditions: progress, challenges, and opportunities

Since Kanner's classic description of the syndrome of early infantile autism in 1943, conceptions of the disorder have evolved while retaining important continuity with what Kanner viewed as the hallmarks of the condition-social impairment (autism) and difficulties in dealing with change in the nonsocial world (insistence on sameness). This paper reviews the history of this evolution and the important potential advantages and disadvantages of changes being contemplated for DSM-5. The convergence of diagnostic approach in DSM-IV and ICD-10 provided a shared system that fostered a tremendous body of research. The changes proposed in DSM-5 may impact both research comparability and service eligibility.

Pharmacologic treatment of repetitive behaviors in autism spectrum disorders: evidence of publication bias

OBJECTIVE

The goal of this study was to examine the efficacy of serotonin receptor inhibitors (SRIs) for the treatment of repetitive behaviors in autism spectrum disorders (ASD).

METHODS

Two reviewers searched PubMed and Clinicaltrials.gov for randomized, double-blind, placebo-controlled trials evaluating the efficacy of SRIs for repetitive behaviors in ASD. Our primary outcome was mean improvement in ratings scales of repetitive behavior. Publication bias was assessed by using a funnel plot, the Egger's test, and a meta-regression of sample size and effect size.

RESULTS

Our search identified 5 published and 5 unpublished but completed trials eligible for meta-analysis. Meta-analysis of 5 published and 1 unpublished trial (which provided data) demonstrated a small but significant effect of SRI for the treatment of repetitive behaviors in ASD (standardized mean difference: 0.22 [95% confidence interval: 0.07-0.37], z score = 2.87, P < .005). There was significant evidence of publication bias in all analyses. When Duval and Tweedie's trim and fill method was used to adjust for the effect of publication bias, there was no longer a significant benefit of SRI for the treatment of repetitive behaviors in ASD (standardized mean difference: 0.12 [95% confidence interval: -0.02 to 0.27]). Secondary analyses demonstrated no significant effect of type of medication, patient age, method of analysis, trial design, or trial duration on reported SRI efficacy.

CONCLUSIONS

Meta-analysis of the published literature suggests a small but significant effect of SRI in the treatment of repetitive behaviors in ASD. This effect may be attributable to selective publication of trial results. Without timely, transparent, and complete disclosure of trial results, it remains difficult to determine the efficacy of available medications.

Sensitivity and specificity of proposed DSM-5 diagnostic criteria for autism spectrum disorder

OBJECTIVE

This study evaluated the potential impact of proposed DSM-5 diagnostic criteria for autism spectrum disorder (ASD).

METHOD

The study focused on a sample of 933 participants evaluated during the DSM-IV field trial; 657 carried a clinical diagnosis of an ASD, and 276 were diagnosed with a non-autistic disorder. Sensitivity and specificity for proposed DSM-5 diagnostic criteria were evaluated using field trial symptom checklists as follows: individual field trial checklist items (e.g., nonverbal communication); checklist items grouped together as described by a single DSM-5 symptom (e.g., nonverbal and verbal communication); individual DSM-5 criterion (e.g., social-communicative impairment); and overall diagnostic criteria.

RESULTS

When applying proposed DSM-5 diagnostic criteria for ASD, 60.6% (95% confidence interval: 57%-64%) of cases with a clinical diagnosis of an ASD met revised DSM-5 diagnostic criteria for ASD. Overall specificity was high, with 94.9% (95% confidence interval: 92%-97%) of individuals accurately excluded from the spectrum. Sensitivity varied by diagnostic subgroup (autistic disorder = 0.76; Asperger's disorder = 0.25; pervasive developmental disorder-not otherwise specified = 0.28) and cognitive ability (IQ < 70 = 0.70; IQ ≥ 70 = 0.46).

CONCLUSIONS

Proposed DSM-5 criteria could substantially alter the composition of the autism spectrum. Revised criteria improve specificity but exclude a substantial portion of cognitively able individuals and those with ASDs other than autistic disorder. A more stringent diagnostic rubric holds significant public health ramifications regarding service eligibility and compatibility of historical and future research.

Autism and related disorders

The pervasive developmental disorders are a group of neurodevelopmental disorders that include autistic disorder, Asperger's disorder, pervasive developmental disorder - not otherwise specified (PDD-NOS), childhood disintegrative disorder (CDD), and Rett's disorder. All feature childhood onset with a constellation of symptoms spanning social interaction and communication and including atypical behavior patterns. The first three disorders (autistic disorder, Asperger's disorder, and PDD-NOS) are currently referred to as autism spectrum disorders, reflecting divergent phenotypic and etiological characteristics compared to Rett's disorder and CDD. This chapter reviews research and clinical information to appropriate medical diagnosis and treatment.

Understanding the social brain in autism

Autism is an early onset neurodevelopmental disorder characterized by disruption of early social interaction. Although the social disability of autism remains the central defining feature of the condition, mechanisms that might account for this disability remain poorly understood. This paper briefly reviews some aspects of the social deficit in autism focusing on new approaches to characterizing social information processing problems, potential brain mechanisms, and theoretical models of the disorder. It will touch on aspects of specific social processes that appear to develop in unusual ways in autism including facial perception, joint attention, and social information processing. The importance of adopting more ecologically valid methods and for integrating the various approaches in deriving new models for social deficits in autism will be highlighted. Future research should build on the emerging synergy of different aspects of social neuroscience.

Structural neural phenotype of autism: preliminary evidence from a diffusion tensor imaging study using tract-based spatial statistics

BACKGROUND AND PURPOSE

There is mounting evidence suggesting widespread aberrations in neural connectivity as the underlying neurobiology of autism. Using DTI to assess white matter abnormalities, this study implemented a voxelwise analysis and tract-labeling strategy to test for a structural neural phenotype in autism.

MATERIALS AND METHODS

Subjects included 15 boys with autism and 8 controls, group-matched on age, cognitive functioning, sex, and handedness. DTI data were obtained by using a 3T scanner. FSL, including TBSS, was used to process and analyze DTI data where FA was chosen as the primary measure of fiber tract integrity. Affected voxels were labeled by using an integrated white matter tractography atlas. Post hoc correlation analyses were performed between FA of each affected fiber tract and scores on the Social Responsiveness Scale.

RESULTS

The autism group exhibited bilateral reductions in FA involving numerous association, commissural, and projection tracts, with the most severely affected being the forceps minor. The most affected association tracts were the inferior fronto-occipital fasciculus and superior longitudinal fasciculus. There were no areas of increased FA in the autism group. All post hoc correlation analyses became nonsignificant after controlling for multiple comparisons.

CONCLUSIONS

This study provides preliminary evidence of reduced FA along many long-range fiber tracts in autism, suggesting aberrant long-range corticocortical connectivity. Although the spatial distribution of these findings suggests widespread abnormalities, there are major differences in the degree to which different tracts are affected, suggesting a more specific neural phenotype in autism.

From Bayes through marginal utility to effect sizes: a guide to understanding the clinical and statistical significance of the results of autism research findings

The objectives of this report are: (a) to trace the theoretical roots of the concept clinical significance that derives from Bayesian thinking, Marginal Utility/Diminishing Returns in Economics, and the "just noticeable difference", in Psychophysics. These concepts then translated into: Effect Size (ES), strength of agreement, clinical significance, and related concepts, and made possible the development of Power Analysis; (b) to differentiate clinical significance from statistical significance; and (c) to demonstrate the utility of measures of ES and related concepts for enhancing the meaning of Autism research findings. These objectives are accomplished by applying criteria for estimating clinical significance, and related concepts, to a number of areas of autism research.

Diffusion tensor imaging in autism spectrum disorders: preliminary evidence of abnormal neural connectivity

OBJECTIVE

This study indirectly tested the hypothesis that individuals with autism spectrum disorders (ASDs) have impaired neural connections between the amygdala, fusiform face area, and superior temporal sulcus, key processing nodes of the 'social brain'. This would be evidenced by abnormalities in the major fibre tracts known to connect these structures, including the inferior longitudinal fasciculus and inferior fronto-occipital fasciculus.

METHOD

Magnetic resonance diffusion tensor imaging was performed on 20 right-handed males (ASD = 10, controls = 10) with a mean age 13.5 ± 4.0 years. Subjects were group-matched according to age, full-scale IQ, handedness, and ethnicity. Fractional anisotropy was used to assess structural integrity of major fibre tracts. Voxel-wise comparison of white matter fractional anisotropy was conducted between groups using ANCOVA adjusting for age, full-scale IQ, and brain volume. Volumes of interest were identified using predetermined probability and cluster thresholds. Follow-up tractography was performed to confirm the anatomic location of all volumes of interest which were observed primarily in peri-callosal regions and the temporal lobes.

RESULTS

The regions of lower fractional anisotropy, as confirmed by tractography, involved the inferior longitudinal fasciculus/inferior fronto-occipital fasciculus, superior longitudinal fasciculus, and corpus callosum/cingulum. Notably, some volumes of interest were adjacent to the fusiform face area, bilaterally, corresponding to involvement of the inferior longitudinal fasciculus. The largest effect sizes were noted for volumes of interest in the right anterior radiation of the corpus callosum/cingulum and right fusiform face area (inferior longitudinal fasciculus).

CONCLUSIONS

This study provides preliminary evidence of impaired neural connectivity in the corpus callosum/cingulum and temporal lobes involving the inferior longitudinal fasciculus/inferior fronto-occipital fasciculus and superior longitudinal fasciculus in ASDs. These findings provide preliminary support for aberrant neural connectivity between the amygdala, fusiform face area, and superior temporal sulcus-temporal lobe structures critical for normal social perception and cognition.

Asperger syndrome

Asperger syndrome (AS) is a chronic neurodevelopmental disorder of social interaction, communication, and a restricted range of behaviors or interests. Although not generally associated with intellectual disability, the severe social disability and, in many cases, associated mental health and other medical problems, result in disability throughout life. The diagnosis is often delayed, sometimes into adulthood, which is unfortunate because there are now a range of interventions available, and the current evidence supports intervention starting as early in childhood as possible. The aim of this review is to present a description of AS, an up to date synopsis of the literature pertaining to its etiology, co-morbidity and intervention options, and a discussion of current nosological controversies.

Autism and autism spectrum disorders: diagnostic issues for the coming decade

A decade and a half have elapsed since DSM-IV and ICD-10 appeared. During this time the convergent definitions of autism and related disorders in these two diagnostic systems have stimulated tremendous research. In this brief review we summarize areas of progress and continuing controversy, including approaches to diagnosis in more cognitively able individuals on the autism spectrum, diagnosis in very young infants, the issue of subtypes, and the potential contribution of genetic research. The use of dimensional assessments has some advantages as do the insights from prospective studies. At this point it will be important to study not only causative factors but developmental processes disrupted in these disorders.

Macrophage migration inhibitory factor and autism spectrum disorders

OBJECTIVE

Autistic spectrum disorders are childhood neurodevelopmental disorders characterized by social and communicative impairment and repetitive and stereotypical behavior. Macrophage migration inhibitory factor (MIF) is an upstream regulator of innate immunity that promotes monocyte/macrophage-activation responses by increasing the expression of Toll-like receptors and inhibiting activation-induced apoptosis. On the basis of results of previous genetic linkage studies and reported altered innate immune response in autism spectrum disorder, we hypothesized that MIF could represent a candidate gene for autism spectrum disorder or its diagnostic components.

METHODS

Genetic association between autism spectrum disorder and MIF was investigated in 2 independent sets of families of probands with autism spectrum disorder, from the United States (527 participants from 152 families) and Holland (532 participants from 183 families). Probands and their siblings, when available, were evaluated with clinical instruments used for autism spectrum disorder diagnoses. Genotyping was performed for 2 polymorphisms in the promoter region of the MIF gene in both samples sequentially. In addition, MIF plasma analyses were conducted in a subset of Dutch patients from whom plasma was available.

RESULTS

There were genetic associations between known functional polymorphisms in the promoter for MIF and autism spectrum disorder-related behaviors. Also, probands with autism spectrum disorder exhibited higher circulating MIF levels than did their unaffected siblings, and plasma MIF concentrations correlated with the severity of multiple autism spectrum disorder symptoms.

CONCLUSIONS

These results identify MIF as a possible susceptibility gene for autism spectrum disorder. Additional research is warranted on the precise relationship between MIF and the behavioral components of autism spectrum disorder, the mechanism by which MIF contributes to autism spectrum disorder pathogenesis, and the clinical use of MIF genotyping.

Genes controlling affiliative behavior as candidate genes for autism

BACKGROUND

Autism spectrum disorders (ASD) are neurodevelopmental disorders of complex etiology, with a recognized substantial contribution of heterogeneous genetic factors; one of the core features of ASD is a lack of affiliative behaviors.

METHODS

On the basis of the existing literature, in this study we examined the hypothesis of allelic associations between genetic variants in six genes involved in control of maternal and affiliative behaviors (OXT, OXTR, PRL, PRLR, DbetaH, and FOSB). One hundred and seventy-seven probands with ASD from 151 families (n = 527) were assessed with a set of related instruments capturing multiple facets of ASD. Multivariate and univariate phenotypes were constructed from these assessments and subjected to genetic linkage and association analyses with PBAT and FBAT software.

RESULTS

The resulting pattern of findings, in general, confirmed the hypotheses of the significance of the genes involved in the development of affiliative behaviors in the manifestation of ASD (p values ranging from .000005 to .05); statistically speaking, the strongest results were obtained for allelic associations with the PRL, PRLR, and OXTR genes.

CONCLUSIONS

These preliminary data provide additional support for the hypothesis that the allelic variants of genes necessary for the development of species-typical affiliative behaviors are associated with ASD. Independent replication of these findings is needed and studies of other genes associated with affiliative behaviors are indicated.

Pragmatic Assessment in Autism Spectrum Disorders: A Comparison of a Standard Measure With Parent Report

The purpose of this study was to investigate the concurrent validity of subtests on the Comprehensive Assessment of Spoken Language (CASL) by comparing them with the assessment of communication and social skills on the Vineland Adaptive Behavior Scales (Vineland). The participants were 35 children and adolescents with higher functioning autism spectrum disorders (ASD) who had received both the CASL and the Vineland. Results of the study suggest that the Pragmatic Judgment and Inferences subtests of the CASL appeared to document the difficulties that individuals with ASD had in adaptive use of language for communication.

Autism in infants: an update

Although autism is a disorder of very early onset, knowledge on how it is first expressed in infancy has, until recently, remained limited. In recent years new strategies of research, including prospective studies, have substantially increased our knowledge regarding autism in infants. Research findings have suggested the very early emergence of significant differences in social information processes. In addition to having important implications for research, these findings also offer new opportunities for screening and early identification and, hopefully, for improved outcome.

Placental trophoblast inclusions in autism spectrum disorder

BACKGROUND

Microscopic examination of placental tissue may provide a route to assessing risk and understanding underlying biology of autism.

METHODS

Occurrence of a distinctive microscopic placental morphological abnormality, the trophoblast inclusion, was assessed using archived placental tissue. The rate of occurrence of trophoblast inclusion-positive slides observed for 13 individuals with autism spectrum disorder (ASD) was compared to the rate in an anonymous consecutive birth cohort.

RESULTS

The occurrence of inclusion positive slides was significantly greater in the ASD group compared to the control group (6/27 slides, 22.2% vs. 12/154, 7.8%; Fisher Exact Test, two-tailed p = .033; relative risk 2.85). The proportion of positive cases was also greater in the ASD group (5/13 cases, 38.5% vs. 8/61, 13.1%; Fisher Exact, two-tailed p = .044; relative risk 2.93). Behavioral severity scores did not differ across groups of inclusion positive (N = 4) and negative (N = 8) ASD individuals.

CONCLUSIONS

Although probably not functionally detrimental or causative, the greater occurrence of placental trophoblast inclusions observed in ASD individuals may reflect altered early developmental processes. Further research is required to replicate the basic finding, to understand the basis for the trophoblastic abnormality, and to determine the utility of the measure in early detection of ASD.

Social and Communication Abilities and Disabilities in Higher Functioning Individuals with Autism Spectrum Disorders: The Vineland and the ADOS

The relationship between adaptive functioning (ability) and autism symptomatology (disability) remains unclear, especially for higher functioning individuals with autism spectrum disorder (ASD). This study investigates ability and disability using the Vineland and Autism Diagnostic Observation Schedule (ADOS), respectively, in two clinical samples of children with ASD. Participants included 187 males with VIQ > 70. Vineland scores were substantially below VIQ, highlighting the magnitude of adaptive impairments despite cognitive potential. A weak relationship was found between ability and disability. Negative relationships were found between age and Vineland scores and no relationships were found between age and ADOS scores. Positive relationships were found between IQ and Vineland Communication. Results stress the need for longitudinal studies on ability and disability in ASD and emphasize the importance of adaptive skills intervention.

Educational placements and service use patterns of individuals with autism spectrum disorders

This project was undertaken to identify child characteristics associated with educational placement and service use in high-functioning children with autism spectrum disorders. The sample of 101 (nine females) had a mean age of 12 +/- 3 years (mean IQ = 101.77 +/- 19.50). Results indicate that lower-cognitive ability and communication skill were associated with placement in special education. Based on parent-report, most students stayed in the same placement (regular or special education) in which they began first grade and the majority of students received special services in their schools (most often speech/language intervention). Findings highlight the emphasis placed on certain child characteristics (e.g., cognitive ability), with far less emphasis on other areas (e.g., degree of social deficit), in educational placement and service provision.

Is there a 'regressive phenotype' of Autism Spectrum Disorder associated with the measles-mumps-rubella vaccine? A CPEA Study

A multi-site study of 351 children with Autism Spectrum Disorders (ASD) and 31 typically developing children used caregiver interviews to describe the children's early acquisition and loss of social-communication milestones. For the majority of children with ASD who had experienced a regression, pre-loss development was clearly atypical. Children who had lost skills also showed slightly poorer outcomes in verbal IQ and social reciprocity, a later mean age of onset of autistic symptoms, and more gastrointestinal symptoms than children with ASD and no regression. There was no evidence that onset of autistic symptoms or of regression was related to measles-mumps-rubella vaccination. The implications of these findings for the existence of a 'regressive phenotype' of ASD are discussed.

Healthcare issues for children on the autism spectrum

PURPOSE OF REVIEW

We provide a summary of issues relevant to healthcare and health delivery in autism and related disorders, with a focus on work published in the past 5 years.

RECENT FINDINGS

Autism has a strong genetic basis as evidenced by the high recurrence rate in families and its associations with Fragile X syndrome and tuberous sclerosis. Early diagnosis of autism is important, given the potential for improvement with intervention. Although its associations have been reported with events such as measles-mumps-rubella immunization, large-scale studies have not supported such links. Controlled drug trials have increased in frequency and drug treatment may be helpful in addressing frequently associated behavioural and emotional difficulties. Alternative treatments are frequently preferred by parents.

SUMMARY

Knowledge of autism among healthcare professionals has increased but gaps remain. Physicians and other professionals can facilitate the delivery of healthcare services to individuals with autism. Awareness of empirically validated treatments will facilitate work with individuals with autism and related disorders as well as with their families.