Epidemiology and demographics

Over 20 epidemiological studies of autism have been conducted, with reported prevalence rates ranging from 0.7 per 10 000 to 21.1 per 10 000 with a median value of prevalence estimate of 4 to 5 per 10 000.(35) Several recent studies have reported somewhat higher rates of the condition, in the order of 1 per 1000; it remains unclear whether the condition has actually increased or whether the apparent increase relates to broader definitions of autism or other factors.

Epidemiological studies have clarified that there is no association of autism with upper socioeconomic status. Early impressions of such associations were the result of referral bias. A number of studies, including both epidemiological and clinically referred samples, report higher rates of autism in boys than in girls (typically 3.5:1 or 4:1). This ratio varies with IQ level, i.e. females with autism who have IQs in the normal range are probably 50 times less common than males. (3.6) The explanation for this sex difference remains unclear. It is possible that the degree of insult required to produce autism in females must be greater than for males.

Aspergers Answers Revealed

Aspergers Answers Revealed

Learn How to Help, Understand amp Cope with your Aspergers Child from a UK Chartered Educational Psychologist. Before beginning any practice relating to Aspergers it is highly recommended that you first obtain the consent and advice of a qualified health,education or social care professional.

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