Importance: Many studies have investigated impairments in cognitive domains in adults with autism spectrum disorder (ASD). Yet, to date, a comprehensive overview on the patterns of cognitive functioning is lacking.
Objective: To provide an overview of nonsocial and social cognitive functioning in various domains in adults with ASD, allowing for comparison of the severity of deficits between different domains.
Data Sources: A literature search performed in an academic medical setting was conducted using PubMed, PsycINFO, Embase, and Medline databases with the combination of the following free-text and Medical Subject Headings where applicable: [cogniti* OR neurocogniti* OR neuropsycholog* OR executive function* OR IQ OR intelligence quotient OR social cognition OR emotion perception OR affect perception OR emotion recognition OR attribution OR ToM OR mentalising OR mentalizing OR prosody OR social knowledge OR mind reading OR social cue OR social judgment] AND [autis* OR ASD OR Asperger OR Asperger's OR PDD OR pervasive developmental disorder]. The search was further limited to studies published between 1980 (first inclusion of autism diagnosis in the DSM-III) and July 2018.
Study Selection: Studies included were published as a primary peer-reviewed research article in English, included individuals with ASD 16 years or older, and assessed at least 1 domain of neurocognitive functioning or social cognition using standard measures.
Data Extraction and Synthesis: Of 9892 articles identified and screened, 75 met the inclusion criteria for the systematic review and meta-analysis.
Main Outcomes and Measures: Hedges g effect sizes were computed, and random-effects models were used for all analyses. Moderators of between-study variability in effect sizes were assessed using meta-regressions.
Results: The systematic review and meta-analysis included 75 studies, with a combined sample of 3361 individuals with ASD (mean [SD] age, 32.0 [9.3] years; 75.9% male) and 5344 neurotypical adults (mean [SD] age, 32.3 [9.1] years; 70.1% male). Adults with ASD showed large impairments in theory of mind (g = -1.09; 95% CI, -1.25 to -0.92; number of studies = 39) and emotion perception and processing (g = -0.80; 95% CI, -1.04 to -0.55; n = 18), followed by medium impairments in processing speed (g = -0.61; 95% CI, -0.83 to -0.38; n = 21) and verbal learning and memory (g = -0.55; 95% CI, -0.86 to -0.25; n = 12). The least altered cognitive domains were attention and vigilance (g = -0.30; 95% CI, -0.81 to 0.21; n = 5) and working memory (g = -0.23; 95% CI, -0.47 to 0.01; n = 19). Meta-regressions confirmed robustness of the results.
Conclusions and Relevance: Results of this systematic review and meta-analysis suggest that adults with ASD show impairments in social cognitive domains and in specific nonsocial cognitive domains. These findings contribute to the understanding of the patterns of cognitive functioning in adults with ASD and may assist in the identification of targets for cognitive interventions.