Comparing autism, PDD-NOS, and other developmental disabilities on parent-reported behavior problems: little evidence for ASD subtype validity

The Future of Disentangling the Heterogeneity of Autism With Neuroimaging Studies

Autism spectrum disorder (ASD) is a lifelong neurodevelopmental condition. Over the past decade, a considerable number of approaches have been developed to identify potential neuroimaging-based biomarkers of ASD that have uncovered specific neural mechanisms that underlie behaviors associated with ASD. However, the substantial heterogeneity among individuals who are diagnosed with ASD hinders the development of biomarkers. Disentangling the heterogeneity of ASD is pivotal to improving the quality of life for individuals with ASD by facilitating early diagnosis and individualized interventions for those who need support. In this review, we discuss recent advances in neuroimaging that have facilitated the characterization of the heterogeneity of this condition using 3 frameworks: neurosubtyping, dimensional models, and normative models. We also discuss the challenges, possible solutions, and clinical utility of these 3 frameworks. We argue that several factors need to be considered when parsing heterogeneity using neuroimaging, including co-occurring conditions, neurodevelopment, heredity and environment, and multisite and multimodal data. We close with a discussion of future directions for achieving a better understanding of the neural mechanisms that underlie neurodevelopmental heterogeneity and the future of precision medicine in ASD.

Investigating the borders of autism spectrum disorder: lessons from the former diagnosis of pervasive developmental disorder not otherwise specified

Introduction

Autism Spectrum Disorder (ASD) diagnosis is relatively consensual in typical forms. The margins of the spectrum and their degree of extension, however, are controversial. This has far-reaching implications, which extend beyond theoretical considerations: first, peripheral forms of autism are more prevalent than central forms; second, we do not know how relevant typical-targeted recommendations are for atypical forms. In DSM-IV-TR, these margins of autism were studied within the category of Pervasive Developmental Disorder - Not Otherwise Specified (PDD-NOS). In spite of its low reliability, this former diagnosis was of particular interest to shed light on the gray area of margins. The aim of this systematic is therefore to investigate the clinical characteristics of PDD-NOS in comparison with Autistic Disorder.

Method

A stepwise systematic PRISMA literature review was conducted by searching PubMed and Web Of Science databases to select corresponding studies.

Results

The systematic review included 81 studies comprising 6,644 children with PDD-NOS. Cross-sectional and longitudinal studies comparing PDD-NOS and AD showed that PDD-NOS corresponds to milder form of autism with less impact and less associated disorder, with the exception of schizophrenia and mood disorder.

Discussion

Our review challenges initial views of PDD-NOS, and shows the clinical relevance of this diagnosis when dealing with the margins of autism, and the de facto diversity included in the spectrum. However, in view of the many limitations of PDD-NOS (low reliability, instability through time, low acceptability), we suggest taxonomic changes in DSM-5: we introduce a new category based on three main dimensions related to socialization impairment, emotional lability and psychotic symptoms.

Conclusion

Our review argues for a distinction between AD and PDD-NOS on clinical characteristics and thus highlights the need to study the margins of autism. While the limitations of the PDD-NOS category made it irrelevant to investigate these margins from a research perspective, we believe that a multidimensional approach for mental health professionals taping socialization, emotion lability and psychotic symptoms would be interesting. Our review therefore encourage future studies to test relevant criteria for a new category and possibly identify developmental trajectories, specific interventions and treatments.

The Diagnosis of "Pervasive Developmental Disorder Not Otherwise Specified": A Systematic Literature Review

(1) Background: The study deepens the diagnosis of "pervasive developmental disorder not otherwise specified" (PDD-NOS), a subthreshold diagnosis introduced in DSM-IV and then absorbed into the broader spectrum disorder of autism in DSM 5. The presence of people still attributed with a diagnosis of PDD-NOS can cause confusion in the understanding of this disorder, which is no longer present in the current diagnostic system. This review aims to gain a deeper understanding of the characteristics and boundaries of diagnosis, its use within the scientific community, and the long-term stability of that diagnosis. (2) Methods: The Prisma method was used to carry out the literature review; the scientific papers were selected using scientific search engines, including SCOPUS, PUBMED, and PsychINFO. Twenty-three articles were finally selected, and a meticulous reading was carried out in relation to the research questions. (3) Results: Four cross-cutting categories were identified: (1) diagnosis; (2) differential diagnosis; (3) prognosis; and (4) comorbidity. (4) Conclusions: Limits have emerged regarding the consistency, sensitivity, and the stability of PDD-NOS. The inclusion of this diagnosis within the broader autism spectrum disorder category coined in DSM-5 appears applicable.

Subdimensions of social-communication behavior in autism-A replication study

Introduction

In order to identify more refined dimensions of social-communication impairments in autism spectrum disorder (ASD) a previous study applied exploratory and confirmatory factor analyses to diagnostic algorithm scores of the autism diagnostic observation schedule (ADOS), Module 3. A three-factor model consisting of repetitive behaviors, impairments in 'Basic Social-Communication' and in 'Interaction quality' (IQ) was established and confirmed. The current study aimed to replicate this model in an independent sample. To advance our understanding of the latent structure of social communication deficits, previous work was complemented by a probabilistic approach.

Methods

Participants (N = 1363) included verbally fluent children and young adults, diagnosed as ASD or non-ASD based on "gold standard" best-estimate clinical diagnosis. Confirmatory factor analysis examined the factor structure of algorithm items from the ADOS Module 3 and correlations with individual characteristics (cognitive abilities, age) were analyzed. Linear Regressions were used to test the contribution of each latent factor to the prediction of an ASD diagnosis. To tackle large inter-correlations of the latent factors, a Bayesian exploratory factor analysis (BEFA) was applied.

Results

Results confirmed the previously reported observation of three latent dimensions in the ADOS algorithm reflecting 'Restricted, Repetitive Behaviors', 'Basic Social-Communication' behaviors and 'Interaction Quality'. All three dimensions contributed independently and additively to the prediction of an ASD diagnosis.

Conclusion

By replicating previous findings in a large clinical sample our results contribute to further conceptualize the social-communication impairments in ASD as two dimensional.

The Diagnosis of Autism: From Kanner to DSM-III to DSM-5 and Beyond

In this paper we review the impact of DSM-III and its successors on the field of autism-both in terms of clinical work and research. We summarize the events leading up to the inclusion of autism as a "new" official diagnostic category in DSM-III, the subsequent revisions of the DSM, and the impact of the official recognition of autism on research. We discuss the uses of categorical vs. dimensional approaches and the continuing tensions around broad vs. narrow views of autism. We also note some areas of current controversy and directions for the future.

A Scoping Review of Anxiety in Young Children with Autism Spectrum Disorder

Research on anxiety in children and adolescents with autism spectrum disorder (ASD) has burgeoned in the past 15 years. Most of the research has focused on school-age children, ages 6 to 18 years. Yet, recent studies suggest that anxiety can emerge in young children, under 6 years, with ASD. This scoping review synthesized the literature on anxiety in young children with ASD. Three domains of anxiety research were reviewed: (a) prevalence/severity, phenomenology, and course; (b) correlates; and (c) treatment. Four online databases were searched from the start of the database until March 2020. Keywords pertaining to anxiety, autism, and young children were entered. The search identified 44 articles for inclusion. These studies varied with respect to sample source, informants, and measures to assess anxiety. The overall prevalence of anxiety ranged from 1.6 to 62%. Sixteen of 17 studies found that young children with ASD had higher levels of anxiety compared to various control groups. A variety of DSM anxiety symptoms and disorders were present in young children with the most common symptoms being specific, social, and generalized fears. Correlates of anxiety included sensory over-responsivity, sleep disturbance, aggression/defiance, and attention deficit/hyperactivity disorder. Three cognitive behavioral treatment studies for anxiety and one developmental intervention targeting ASD symptoms showed promise in reducing anxiety. Findings indicate an early emergence of anxiety in some children with ASD. Further research on the measurement, pathophysiology, and treatment of anxiety in early childhood is critical to improving outcomes in children with ASD. LAY SUMMARY: This scoping review synthesizes the literature on anxiety in young children with autism spectrum disorder (ASD). Results indicate that children with ASD have higher levels of anxiety than children without ASD. Potential factors that could be contributing to anxiety include sensory, sleep, and behavioral problems. Preliminary studies show that anxiety can improve with cognitive behavioral treatment. These findings suggest that research on anxiety in young children with ASD should be prioritized to improve mental health outcomes.

Evaluation of sleep disturbances, gastrointestinal problems and eating behaviors in Turkish children with autistic disorder and PDD-NOS

Purpose

The purpose of this study is to evaluate the relationship between sleep disturbances, gastrointestinal (GI) problems and eating behaviors in children who are diagnosed with autistic disorder (AD) and pervasive developmental disorder not otherwise specified (PDD-NOS).

Design/methodology/approach

This study was conducted with 102 children who were diagnosed with autism spectrum disorder (ASD). Sleeping and GI (abdominal pain, constipation, diarrhea, vomiting, difficulty swallowing) problems in children were obtained by asking their parents using a questionnaire. The feeding assessment survey (FAS), brief autism mealtime behavior inventory (BAMBI) and food consumption frequency were used to obtain information about the children’s eating habits.

Findings

The BAMBI total score, food refusal and features of autism subscale scores of those with AD were higher than those in the PDD-NOS group (p < 0.05). Sleeping, GI and eating problems are seen in those with AD more commonly than in those diagnosed with PDD-NOS.

Originality/value

To the knowledge, this is the first study that compares GI, sleeping and eating problems in children with AD and PDD-NOS. Sleeping, GI and eating problems may be more frequent in children with AD than in those with PDD-NOS. The GI problem rate is higher in children with autism with sleeping problems than without sleeping problems.

Classifying Autism Spectrum Disorders by ADI-R: Subtypes or Severity Gradient?

To reduce phenotypic heterogeneity of Autism spectrum disorders (ASD) and add to the current diagnostic discussion this study aimed at identifying clinically meaningful ASD subgroups. Cluster analyses were used to describe empirically derived groups based on the Autism Diagnostic Interview-revised (ADI-R) in a large sample of n = 463 individuals with ASD aged 3-21. Three clusters were observed. Most severely affected individuals regarding all core symptoms were allocated to cluster 2. Cluster 3 comprised moderate symptom severity of social communication impairments (SCI) and less stereotyped repetitive behavior (RRB). Minor SCI and relatively more RRB characterized cluster 1. This study offers support for both, a symptom profile, and a gradient model of ASD within the spectrum due to the sample included.

Perceived Social Competence and Loneliness Among Young Children with ASD: Child, Parent and Teacher Reports

Perceived loneliness and social competence were assessed for 127 children with ASD without comorbid ID, 4-7 years old, through child self-report. Using an abbreviated version of the Loneliness and Social Dissatisfaction Questionnaire (LSDQ; Cassidy and Asher in Child Dev 63:250-365, 1992), the majority of children reported friendships, yet a considerable proportion also reported social difficulties. Factor analysis of the abbreviated LSDQ identified three factors, which were significantly associated with parent- and teacher-reported variables. Regression analyses revealed parent-reported social skills deficits and teacher-reported conflict in the student-teacher relationship to be associated with child-reported loneliness. Implications for practice are discussed.

Autism spectrum disorder and attention-deficit/hyperactivity disorder in early childhood: A review of unique and shared characteristics and developmental antecedents

Autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD) have overlapping characteristics and etiological factors, but to which extent this applies to infant- and preschool age is less well understood. Comparing the pathways to ASD and ADHD from the earliest possible stages is crucial for understanding how phenotypic overlap emerges and develops. Ultimately, these insights may guide preventative and therapeutic interventions. Here, we review the literature on the core symptoms, temperament and executive function in ASD and ADHD from infancy through preschool age, and draw several conclusions: (1) the co-occurrence of ASD and ADHD increases with age, severity of symptoms and lower IQ, (2) attention problems form a linking pin between early ASD and ADHD, but the behavioral, cognitive and sensory correlates of these attention problems partly diverge between the two conditions, (3) ASD and ADHD share high levels of negative affect, although the underlying motivational and behavioral tendencies seem to differ, and (4) ASD and ADHD share difficulties with control and shifting, but partly opposite behaviors seem to be involved.

A genome-wide association study of autism using the Simons Simplex Collection: Does reducing phenotypic heterogeneity in autism increase genetic homogeneity?

BACKGROUND

Phenotypic heterogeneity in autism has long been conjectured to be a major hindrance to the discovery of genetic risk factors, leading to numerous attempts to stratify children based on phenotype to increase power of discovery studies. This approach, however, is based on the hypothesis that phenotypic heterogeneity closely maps to genetic variation, which has not been tested. Our study examines the impact of subphenotyping of a well-characterized autism spectrum disorder (ASD) sample on genetic homogeneity and the ability to discover common genetic variants conferring liability to ASD.

METHODS

Genome-wide genotypic data of 2576 families from the Simons Simplex Collection were analyzed in the overall sample and phenotypic subgroups defined on the basis of diagnosis, IQ, and symptom profiles. We conducted a family-based association study, as well as estimating heritability and evaluating allele scores for each phenotypic subgroup.

RESULTS

Association analyses revealed no genome-wide significant association signal. Subphenotyping did not increase power substantially. Moreover, allele scores built from the most associated single nucleotide polymorphisms, based on the odds ratio in the full sample, predicted case status in subsets of the sample equally well and heritability estimates were very similar for all subgroups.

CONCLUSIONS

In genome-wide association analysis of the Simons Simplex Collection sample, reducing phenotypic heterogeneity had at most a modest impact on genetic homogeneity. Our results are based on a relatively small sample, one with greater homogeneity than the entire population; if they apply more broadly, they imply that analysis of subphenotypes is not a productive path forward for discovering genetic risk variants in ASD.

DSM-5 ASD moves forward into the past

The fifth edition of the diagnostic and statistical manual of mental disorders (DSM-5) (APA in diagnostic and statistical manual of mental disorders, Author, Washington, 2013) has decided to merge the subtypes of pervasive developmental disorders into a single category of autism spectrum disorder (ASD) on the assumption that they cannot be reliably differentiated from one another. The purpose of this review is to analyze the basis of this assumption by examining the comparative studies between Asperger's disorder (AsD) and autistic disorder (AD), and between pervasive developmental disorder not otherwise specified (PDDNOS) and AD. In all, 125 studies compared AsD with AD. Of these, 30 studies concluded that AsD and AD were similar conditions while 95 studies found quantitative and qualitative differences between them. Likewise, 37 studies compared PDDNOS with AD. Nine of these concluded that PDDNOS did not differ significantly from AD while 28 reported quantitative and qualitative differences between them. Taken together, these findings do not support the conceptualization of AD, AsD and PDDNOS as a single category of ASD. Irrespective of the changes proposed by the DSM-5, future research and clinical practice will continue to find ways to meaningfully subtype the ASD.

Making sense of autism: Progressive engagement with science among parents of young, recently diagnosed autistic children

This exploratory study examines the significance of science to parents whose children were recently diagnosed with an autism spectrum disorder. It asks: (I) In what manner did science emerge in parents' concerns and resources as they attempted to understand and advocate for their children? (2) Did some parents engage with science in a qualitatively deeper or more intense manner? Using longitudinal data from interviews and a novel data collection strategy called engagement mapping, it shows that parents asked questions and used resources that were strongly associated with science, but these were vastly outnumbered by "near-science" concerns and resources that mingled meanings from science and daily life. Several parents in the study wove together concerns and resources in an iterative pattern referred to here as progressive engagement with science.

Autism traits in children and adolescents with Cornelia de Lange syndrome

Cornelia de Lange syndrome (CdLS) is a cohesinopathy causing delayed growth and limb deficits. Individuals with CdLS have mild to profound intellectual disability and autistic features. This study characterizes the behavioral phenotype of children with CdLS, focusing on autistic features, maladaptive behaviors, and impact of age. Children with CdLS (5-18 years) were administered normed instruments to characterize autism features (Childhood Autism Rating Scale, CARS), maladaptive behaviors (Aberrant Behavior Checklist), and adaptive skills (Vineland Adaptive Behaviors Scales). CdLS features and severity were rated with Diagnostic Criteria for CdLS. Forty-one children with CdLS (23 females, 18 males) were classified as having "no autism" (n = 7; 17.1%), "mild autism" (n = 17; 41.4%), and "severe autism" (n = 17; 41.4%), using CARS scores. Characteristic items were abnormal emotional response, stereotypies, odd object use, rigidity, lack of verbal communication, and low intellectual functioning. Verbal communication deficits and repetitive behaviors were higher compared to sensory, social cognition, and behavior abnormalities (P ≤ 0.0001). Maladaptive behaviors associated with autism traits were stereotypies (P = 0.003), hyperactivity (P = 0.01), and lethargy (P = 0.03). Activities of daily living were significantly affected; socialization adaptive skills were a relative strength. However, with advancing age, both socialization (P < 0.0001) and communication (P = 0.001) domains declined significantly. CdLS is characterized by autistic features, notably excessive repetitive behaviors and expressive language deficits. While other adaptive skills are impacted, socialization adaptive skills are less affected. Advancing age can worsen communication and socialization deficits relative to neurotypical peers.

Empirically based phenotypic profiles of children with pervasive developmental disorders: interpretation in the light of the DSM-5

This study aimed to contribute to the Diagnostic and Statistical Manual (DSM) debates on the conceptualization of autism by investigating (1) whether empirically based distinct phenotypic profiles could be distinguished within a sample of mainly cognitively able children with pervasive developmental disorder (PDD), and (2) how profiles related to diagnoses and co-occurring behavioral and emotional problems. Six classes with distinct profiles were discerned. Three classes showed profiles not completely in line with the proposed DSM-5 conceptualization of autism. These classes included relatively many cognitively able individuals with PDD-not otherwise specified. However, profiles seemed to suit other diagnostic categories, such as social communication disorder. These alternative diagnoses could retain eligibility for services, and might adequately fit more specifically targeted interventions.

Comorbid atypical autistic traits as a potential risk factor for suicide attempts among adult depressed patients: a case-control study

BACKGROUND

The present study aims to examine if autism spectrum disorder (ASD) is a risk factor for suicide attempts among adult depressed patients and to elucidate the characteristics of suicide attempts in adult depressed patients with ASD.

METHODS

We conducted a case-control study. Subjects consisted of 336 retrospectively recruited first-time visit patients to our outpatient clinic with a current major depressive episode; 31 of the 336 patients had attempted suicide. The demographic backgrounds (i.e., age, gender, personal/family history of suicidality); specific psychopathology like bipolarity, agitation, and psychotic features; and comorbidity such as physical diseases, alcohol abuse, cluster B personality disorder, and ASD including pervasive developmental disorder not otherwise specified (PDD-NOS) were examined as potential risk factors for suicide attempts. We compared these variables between the suicide attempters and non-attempters. In addition, we compared suicide attempters to non-attempters within the ASD group and non-ASD group. Binary logistic regression analysis was performed using the significant independent variables from the comparisons between the suicide attempters and non-attempters, and the odds ratios (OR) and 95% confidence intervals (CI) were calculated.

RESULTS

Logistic regression analysis demonstrated that agitation during a depressive episode (OR = 7.15, 95% CI = 2.88-17.74), past suicidal behaviors (OR = 4.32, 95% CI =1.70-10.98), and comorbid PDD-NOS (OR = 4.04, 95% CI = 1.20-13.54) were significantly associated with suicide attempts. The most prevalent suicidal method was drug overdose (59.1%) among non-ASD attempters while hanging was the most prevalent (44.4%) in ASD attempters.

CONCLUSIONS

Depressed adults with comorbid atypical autistic traits are at higher risk for suicide attempts and may engage in methods that are more lethal.

Narrowly versus broadly defined autism spectrum disorders: differences in pre- and perinatal risk factors

This study examined the differential contribution of pre- and perinatal risks in narrowly versus broadly defined autism spectrum disorder (ASD) and across core symptom domains, IQ and co-morbid problems. Children with a DSM-IV diagnosis of autistic disorder (AD) (n = 121) or pervasive developmental disorder not otherwise specified (PDD-NOS) (n = 75) were compared to a typical control sample (n = 311). Diagnoses were based on extensive assessments between 12 and 49 months of age (M = 33.3, SD = 6.4) and re-evaluated at 43-98 months (M = 68.1, SD = 10.7) in 70% of the cases. Compared with controls, cases with ASD were more likely to be firstborn and show a suboptimal condition after birth. Case mothers reported more infections and more stress during pregnancy. Although the ASD subgroups showed mostly overlapping risks, cases with PDD-NOS differed from those with AD by higher exposure to smoking during pregnancy (SDP) and by a negative association of smoking with IQ, regardless of confounders. SDP appears to contribute more to broadly defined (PDD-NOS) than to narrowly defined ASD (AD). Findings suggest differences in etiological contributors between ASD phenotypes.

Does a claims diagnosis of autism mean a true case?

The purpose of this study was to validate autism spectrum disorder cases identified through claims-based case identification algorithms against a clinical review of medical charts. Charts were reviewed for 432 children who fell into one of the three following groups: (a) more than or equal to two claims with an autism spectrum disorder diagnosis code (n = 182), (b) one claim with an autism spectrum disorder diagnosis code (n = 190), and (c) those who had no claims for autism spectrum disorder but had claims for other developmental or neurological conditions (n = 60). The algorithm-based diagnoses were compared with documented autism spectrum disorders in the medical charts. The algorithm requiring more than or equal to two claims for autism spectrum disorder generated a positive predictive value of 87.4%, which suggests that such an algorithm is a valid means to identify true autism spectrum disorder cases in claims data.

Patterns and predictors of anxiety among siblings of children with autism spectrum disorders

The purpose of this study was to examine patterns of anxiety among siblings of children with autism spectrum disorders (ASD), and determine the characteristics of the child with ASD and their parents that predicted anxiety. Data was collected from 1,755 siblings of children with ASD whose families participated in the Simons Simplex Collection; siblings ranged in age from 3 to 18 years (M = 9 years). Male siblings were at increased risk for sub-clinical anxiety problems during middle childhood. Parental history of anxiety disorders, higher maternal pragmatic language, and more proband behavior problems predicted higher anxiety. While siblings overall did not show elevated anxiety symptoms, higher rates of sub-clinical anxiety problems among males and siblings in middle childhood are cause for concern.

DSM-5 and autism spectrum disorders (ASDs): an opportunity for identifying ASD subtypes

The heterogeneous clinical presentations of individuals with autism spectrum disorders (ASDs) poses a significant challenge for sample characterization and limits the interpretability and replicability of research studies. The Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-5) diagnostic criteria for ASD, with its dimensional approach, may be a useful framework to increase the homogeneity of research samples. In this review, we summarize the revisions to the diagnostic criteria for ASD, briefly highlight the literature supporting these changes, and illustrate how DSM-5 can improve sample characterization and provide opportunities for researchers to identify possible subtypes within ASD.

The persistence and stability of psychiatric problems in adolescents with autism spectrum disorders

BACKGROUND

Psychiatric problems are common in autism spectrum disorders (ASDs), but the reasons are poorly understood. We use a longitudinal population-representative cohort to examine for the first time the persistence of psychiatric problems and to identify risk factors for their occurrence and stability.

METHODS

Eighty-one 16-year olds (75 male, six female), initially seen at 12 years, were re-assessed using the parent-report Strengths and Difficulties Questionnaire (SDQ). Child, family and contextual characteristics from age 12 were tested as risk factors for psychopathology.

RESULTS

Prevalence rates varied depending on whether general population or ASD-specific SDQ cut-offs were used. While the former suggested a decrease in psychiatric problems over time, the ASD-specific cut-offs showed no significant differences. With the exception of ADHD, the ASD-specific cut-offs identified a smaller proportion of individuals as 'affected' than did the general population cut-offs. There was longitudinal domain specificity, with parent correlations ranging from 0.50 to 0.58 and teacher SDQ reports at age 12 correlating 0.33-0.53 with parent reports at 16 years. In examining the role of risk factors, lower IQ and adaptive functioning predicted higher hyperactivity and total difficulties scores. Greater emotional problems at 16 were predicted by poorer maternal mental health, family-based deprivation and lower social class. Improvement from 12 to 16 years in conduct problems was predicted by greater neighbourhood deprivation and special school attendance.

CONCLUSIONS

This is the first longitudinal study of other psychiatric symptoms in ASD. Additional psychiatric problems in ASD are persistent and domain-specific from childhood to adolescence. The finding that age-related reduction in SDQ symptoms does not apply when ASD-specific cut-offs are used requires further evaluation using diagnostic measures. Only a few of the expected risk factor-psychopathology predictions expected from general population studies were found, raising the possibility that the causes of psychopathology in ASD differ from those in the general population.

The association of quality of social relations, symptom severity and intelligence with anxiety in children with autism spectrum disorders

Limited quality of social relations, milder symptom severity and higher intelligence were shown to account for higher anxiety levels in autism spectrum disorders. The current study replicated and extended earlier findings by combining these three determinants of anxiety in autism spectrum disorders in one study. The sample consisted of 134 school-aged children with autism spectrum disorders, of whom 58 (43%) had a co-morbid anxiety disorder according to the Diagnostic Interview Schedule for Children-Parent version. In this sample, we tested associations between these determinants and anxiety univariately and multivariately to clarify the unique contribution of all determinants. Since we hypothesized that the association between limited quality of social relations and anxiety would be amplified by low symptom severity and/or high intelligence, we additionally tested for moderating effects. We found that higher anxiety levels were associated with a lower quality of social relations and lower symptom severity. In this mainly high-functioning sample, intelligence was not related to anxiety levels. No moderation effects were found. Since lower quality of social relations and lower symptom severity are associated with higher anxiety levels in children with autism spectrum disorders, therapeutic interventions aimed at reducing anxiety in autism spectrum disorders should pay attention to improving social relations, and presumably children with a lower symptom severity could benefit most from such interventions.