Autism-Open Access
Open Access

A Theory on Epidemiology of Autism Circumstances

Robert Mahapatra^{* *}Correspondence: Robert Mahapatra, Department of Neuropsychiatry, Central Institute of Psychiatry, Jharkhand, India, Email:

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Epidemiological surveys of autism started in England and since then been conducted in many countries. All epidemiological surveys have focused on a psychiatric-diagnostic approach to autism that has relied over time on different sets of criteria. Thus, it is concerned with autism defined as a severe developmental disorder and not with more subtle autistic features or symptoms that occur as part of other developmental disorders or as unusual personality traits. Most surveys have relied on operational definitions of autism, be they embodied by official classifications or not, and have used the clinical judgment of experts to arrive at the final case groupings. It is worth emphasizing that the field trials of recent classifications such as DSM-III-R or DSM-IV} ICD-10) have also relied upon the judgment of clinical experts as a gold standard to diagnose autism. Therefore, it was conducted while recognizing the differences of particular diagnostic systems available in the last decades to define autism while making no a priori assumptions on their superiority relative to expert clinical judgment. The aims of this article are to provide an up-to date of the methodological features and substantive results of published studies.

Rates of medical conditions associated with autism were reported in 11 surveys. It will be appreciated that these medical conditions were investigated by very different means ranging from questionnaires to full medical work-ups. However, some consistent findings derive from epidemiological samples. Some investigators have mentioned the possibility that rates of autism might be higher among immigrants. Five of the 17 children with autism identified in the Camber well study were from Caribbean origin and the estimated rate of autism was 6 ± 3}10,000 for this group as compared to 4 ± 4}10,000 for the rest of the population. However, the wide confidence intervals associated with rates from this study. Indicate no statistically significant difference. In addition, this area of London had received a large proportion of immigrants from the Caribbean region and, under circumstances where migration fluxes in and out of an area are happening, estimation of population rates should be viewed with much caution. Yet, Afro-Caribbean children referred from the same area were recently found to have higher rates of autism than referred controls; however, the sample was again very small (N¯18) and differential referral patterns to a tertiary center also providing services for the local area could not be ruled out. It is worth noting that only one child was born from British-born Afro-Caribbean parents in a recent survey. Twelve of the 23 studies provided information on the social class of the families of autistic children. Of these, four studies, suggested an association between autism and social class or parental education. The year of data collection for these four investigations and all eight studies conducted thereafter provided no evidence for the association. Thus, the epidemiological results suggest that the earlier findings were probably due to artifacts in the availability of services and in the case-finding methods, as already shown in other samples.

Epidemiological surveys of autism have been extremely useful in establishing a baseline on the prevalence of this severe developmental disorder and in providing a relatively unbiased picture of its main correlates. Despite the methodological differences across surveys, survey results showed a fair amount of consistency, both for rates and correlates. Rates for the schoolage period tended to be higher, reflecting more effective case identification methods at that age, and the median rate in 11 surveys with available estimates for this age group was 5 ± 0}10 000. Found that about half the surveys were consistent with population values of 5 ± 4–5}10 000. Based on these two highly convergent findings, the figure of 5 ± 5}10 000 appears to be the most robust estimate for the prevalence of autism currently available. The epidemiological surveys mentioned in this are now well established and relies on a multi-stage case finding method. Epidemiological surveys can provide an invaluable starting point for the investigation of developmental disorders in countries where such investigations have not yet been conducted. By and large, we observed that the rate proportion for mental imbalance and other non-medically introverted inescapable formative problems to that of barely characterized autism chemical imbalance was 2 ± 6.