Adults with autism spectrum disorder (ASD) are thought to be at disproportionate risk of developing mental health comorbidities, with anxiety and depression being considered most prominent amongst these. Yet, no systematic review has been carried out to date to examine rates of both anxiety and depression focusing specifically on adults with ASD. This systematic review and meta-analysis examined the rates of anxiety and depression in adults with ASD and the impact of factors such as assessment methods and presence of comorbid intellectual disability (ID) diagnosis on estimated prevalence rates. Electronic database searches for studies published between January 2000 and September 2017 identified a total of 35 studies, including 30 studies measuring anxiety (n = 26 070; mean age = 30.9, s.d. = 6.2 years) and 29 studies measuring depression (n = 26 117; mean age = 31.1, s.d. = 6.8 years). The pooled estimation of current and lifetime prevalence for adults with ASD were 27% and 42% for any anxiety disorder, and 23% and 37% for depressive disorder. Further analyses revealed that the use of questionnaire measures and the presence of ID may significantly influence estimates of prevalence. The current literature suffers from a high degree of heterogeneity in study method and an overreliance on clinical samples. These results highlight the importance of community-based studies and the identification and inclusion of well-characterized samples to reduce heterogeneity and bias in estimates of prevalence for comorbidity in adults with ASD and other populations with complex psychiatric presentations.

Anxiety-related difficulties are common in ASD, but measuring anxiety reliably and validly is challenging. Despite an increasing number of studies, there is no clear agreement on which existing anxiety measure is more psychometrically sound and what is the factor structure of anxiety in ASD. The present study examined the internal consistency, convergent, divergent, and discriminant validity, as well as the factor structure of the Spence Children's Anxiety Scale-Parent Version (SCAS-P), in a large international pooled sample of 870 caregivers of youth with ASD from 12 studies in the United Kingdom, United States, and Singapore who completed the SCAS-P. Most were community recruited, while the majority had at least one measure of ASD symptomatology and either cognitive or adaptive functioning measures completed. Existing SCAS-P total scale and subscales had excellent internal consistency and good convergent, divergent and discriminant validity similar to or better than SCAS-P properties reported in typically developing children, except for the poorer internal consistency of the physical injury subscale. Confirmatory Factor Analysis (CFA) of the existing SCAS-P six-correlated factor structure was a poor fit for this pooled database. Principal component analysis using half of the pooled sample identified a 30-item five correlated factor structure, but a CFA of this PCA-derived structure in the second half of this pooled sample revealed a poor fit, although the PCA-derived SCAS-P scale and subscales had stronger validity and better internal consistency than the original SCAS-P. The study's limitations, the use of the SCAS-P to screen for DSM-derived anxiety problems in ASD and future research directions are discussed. Autism Res 2017, 10: 1629-1652. © 2017 International Society for Autism Research, Wiley Periodicals, Inc.

Anxiety is common in autism spectrum disorder. Many anxiety symptoms in autism spectrum disorder are consistent with Diagnostic and Statistical Manual of Mental Disorders (5th ed.) anxiety disorders (termed “common” anxieties), but others may be qualitatively different, likely relating to autism spectrum disorder traits (herein termed “autism-related” anxieties). To date, few studies have examined both “common” and “autism-related” anxiety experiences in autism spectrum disorder. We explored caregiver-reported Spence Children’s Anxiety Scale-Parent version data from a multi-site (United Kingdom, Singapore, and United States) pooled database of 870 6- to 18-year-old participants with autism spectrum disorder, of whom 287 provided at least one written response to the optional open-ended Spence Children’s Anxiety Scale-Parent item 39 (“ Is there anything else your child is afraid of?”). Responses were thematically coded to explore (a) common and autism-related anxiety presentations and (b) their relationship with young people’s characteristics. Nearly half of the responses were autism-related anxieties (mostly sensory, uncommon, or idiosyncratic specific phobias and worries about change and unpredictability). The other half described additional common anxieties not covered in the original measure (mostly social, weather and environmental disasters, and animals). Caregivers of participants who were more severely affected by autism spectrum disorder symptoms reported more autism-related, as compared to common, additional anxieties. Implications for the assessment and understanding of anxiety in autism are discussed.

The present study aimed to examine anxiety profiles among children and adolescents on the autism spectrum. It further aimed to characterize the association between the identified anxiety profiles and key clinical and developmental variables. The Spence Children's Anxiety Scale‐Parent Version (SCAS‐P) data from a large international pooled sample of 870 caregivers of autistic children and adolescents (Mage = 11.6 years, SDage = 2.77; 107 females) was used. Latent profile analysis identified a three‐anxiety profile solution exhibiting high entropy (0.80) and high latent profile probabilities, with good classification accuracy. Identified profiles fell along the severity spectrum and were named as the mild (n = 498), moderate (n = 272) and severe (n = 100) anxiety profiles. There were no statistically significant differences between the three anxiety profiles in terms of sex distribution. Participants in the mild profile were significantly younger than those in the severe profile, had significantly fewer social communication difficulties than youth in the moderate anxiety profile group and had significantly fewer restricted and repetitive behaviors and lower cognitive functioning scores compared to participants in moderate and severe anxiety profiles. This is the first study to move beyond identifying associations and group‐level differences to exploring and identifying characteristics of anxiety‐based subgroups at an individual level that differ on key clinical and developmental variables. The subgroups identified in this study are a preliminary, yet important, first step towards informing future assessment and individualized interventions aiming to support young people on the autism spectrum to reduce and manage anxiety. Lay Summary This study tried to understand if there are subgroups of autistic young people who may have similar anxiety profiles. We found that we could meaningfully group young people into three groups based on how severe the anxiety symptoms their caregivers reported were: a group with low levels of anxiety, those with moderate anxiety, and those with more severe anxiety. We also found that the young people in the mild group were younger, had fewer autism traits and lower levels of intellectual functioning than young people in the other two groups.

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