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A wide variety of postnatal contributors to autism have been proposed, including gastrointestinal or immune system abnormalities, allergies, and exposure of children to drugs, infection, certain foods, or heavy metals. The evidence for these risk factors is anecdotal and has not been confirmed by reliable studies.
Diagnosis of autism. The diagnosis of autism is based on a person's reported and directly observed behavior. [1] There are no known biomarkers for autism spectrum conditions that allow for a conclusive diagnosis. [2] In most cases, diagnostic criteria codified in the World Health Organization 's International Classification of Diseases (ICD) or ...
A 2003 review of epidemiological studies of children found autism rates ranging from 0.03 to 4.84 per 1,000, with the ratio of autism to Asperger syndrome ranging from 1.5:1 to 16:1; [145] combining the geometric mean ratio of 5:1 with a conservative prevalence estimate for autism of 1.3 per 1,000 suggests indirectly that the prevalence of AS ...
A study of 99 autistic probands which found a 2.9% concordance for autism in siblings, and between 12.4% and 20.4% concordance for a "lesser variant" of autism. [8] A study of 31 siblings of autistic children, 32 siblings of children with developmental delay, and 32 controls.
The epidemiology of autism is the study of the incidence and distribution of autism spectrum disorders (ASD). A 2022 systematic review of global prevalence of autism spectrum disorders found a median prevalence of 1% in children in studies published from 2012 to 2021, with a trend of increasing prevalence over time.
It was presumed initially that there was a common cause at the genetic, cognitive, and neural levels for classic autism's characteristic triad of symptoms. [35] However, over time, there was increasing evidence that autism was instead a complex and highly heritable disorder whose core aspects have distinct causes which often co-occur. [35] [36 ...
The World Health Organization estimates about 1 in 100 children had autism during the period from 2012 to 2021 as that was the average estimate in studies published during that period with a trend of increasing prevalence over time. However, the study's 1% figure may reflect an underestimate of prevalence in low-and middle-income countries.
The mechanisms of autism are the molecular and cellular processes believed to cause or contribute to the symptoms of autism. Multiple processes are hypothesized to explain different autism spectrum features. These hypotheses include defects in synapse structure and function, [1][2] reduced synaptic plasticity, [3] disrupted neural circuit ...