Global prevalence of autism: A systematic review update

Abstract

Prevalence estimates of autism are essential for informing public policy, raising awareness, and developing research priorities. Using a systematic review, we synthesized estimates of the prevalence of autism worldwide. We examined factors accounting for variability in estimates and critically reviewed evidence relevant for hypotheses about biological or social determinants (viz., biological sex, sociodemographic status, ethnicity/race, and nativity) potentially modifying prevalence estimates of autism. We performed the search in November 2021 within Medline for studies estimating autism prevalence, published since our last systematic review in 2012. Data were extracted by two independent researchers. Since 2012, 99 estimates from 71 studies were published indicating a global autism prevalence that ranges within and across regions, with a median prevalence of 100/10,000 (range: 1.09/10,000 to 436.0/10,000). The median male‐to‐female ratio was 4.2. The median percentage of autism cases with co‐occurring intellectual disability was 33.0%. Estimates varied, likely reflecting complex and dynamic interactions between patterns of community awareness, service capacity, help seeking, and sociodemographic factors. A limitation of this review is that synthesizing methodological features precludes a quality appraisal of studies. Our findings reveal an increase in measured autism prevalence globally, reflecting the combined effects of multiple factors including the increase in community awareness and public health response globally, progress in case identification and definition, and an increase in community capacity. Hypotheses linking factors that increase the likelihood of developing autism with variations in prevalence will require research with large, representative samples and comparable autism diagnostic criteria and case‐finding methods in diverse world regions over time. Lay Summary We reviewed studies of the prevalence of autism worldwide, considering the impact of geographic, ethnic, and socioeconomic factors on prevalence estimates. Approximately 1/100 children are diagnosed with autism spectrum disorder around the world. Prevalence estimates increased over time and varied greatly within and across sociodemographic groups. These findings reflect changes in the definition of autism and differences in the methodology and contexts of prevalence studies.

Two Genetic Mechanisms in Two Siblings with Intellectual Disability, Autism Spectrum Disorder, and Psychosis

“…Intellectual disability (ID) and autism spectrum disorder (ASD) are common neurodevelopmental disorders. The prevalence of ID is around 1–3% in the general population worldwide [ 1 , 2 , 3 ], while the global prevalence of ASD is approximately 1% [ 4 ]. ID and ASD are complex disorders with high clinical heterogeneity and etiological complexity.…”

“…ID and ASD are complex disorders with high clinical heterogeneity and etiological complexity. Approximately 33% of patients with ASD are comorbid with ID [ 4 ], while ID often co-occurs with behavioral and psychiatric conditions [ 5 , 6 , 7 ]. ID and ASD have high genetic components in their etiology, and the genetic deficits of ID and ASD are highly heterogeneous, ranging from chromosomal abnormalities and copy number variations of genomic DNA (CNV) to small insertions and deletions (indel) and single nucleotide variants (SNV) [ 8 , 9 ].…”

Infantile neurodevelopmental outcome after fetoscopic laser photocoagulation for twin-to-twin transfusion syndrome: the first prospective experience from Iran

“…Otherwise, NDI was not different according to the TTTS stages. Autism was found in two infants in our study (5%) which was the first report of this condition after FLC, although it is greater than general population (0.1%) [ 13 ]. It may be explained by the twinning process, which is a main risk factor for the development of autism [ 14 ].…”

Improvement of the Clinical and Psychological Profile of Patients with Autism after Methylcobalamin Syrup Administration

“…The existing autism prevalence estimates are divergent. Recent reports show a 0.62–0.70% prevalence of autism worldwide and a 1–2% prevalence in a large-scale survey [ 1 ], while the incidence of occurrence continues to rise [ 2 ]. The epidemiology of autism is not strongly affected by geographic region, ethnic/cultural, or socioeconomic factors [ 3 ], but males are affected two-to-five times more often than females [ 1 , 4 ].…”