CHAPTER 6: CONCLUSIONS AND RECOMMENDATIONS
2.5 THE PREVALENCE OF AUTISM
2.4.3 Other studies in progress
Currently, at the University of California, research is being conducted in the study of hair,blood,urine and tissue samples from family members of individuals with autism, to test for 17 metals, traces of pesticides, opioids and other toxicants (Wallis, 2006).
Some experts believe that the rise in autism is due to diet, vaccines and exposure to pesticides, which affect those with a genetic predisposition to autism (London Daily Mail, 2006). As researchers are still not completely sure what causes autism, it is necessary to continue research into possible causal factors. This is also important to help determine appropriate intervention strategies (c.f. 3.2), which the .educator or other professionals might use within the context of inclusive education,either in a full service school, or a special school suitable for supporting the learner with autism (c.f.
1.2).
173 % increase in the number of learners with autism in public schools, from 1992 to 1997 (Sicile-Kira,2003). The U.S. Centre for Disease Control identified it as a public health crisis in 1999 that warranted immediate attention; that autism is the fastest growing developmental disability in the United States. The calculated rate in 1999 was 0.6 - 1.0 % of the general population of school-age learners (Peeters and Gillberg, 1999:39). The rates in adults were expected to be of the same scale as those in children. At present, the prevalence of all PDD in the USA is 1 in 166 children;
double the rate of 10 years ago (Baird et al.,2006;Autism Society of America, 2006; Wallis,2006; Grinker,2007).
According to the AP A (2000),epidemiological studies show the rate of the disorder as being 5 cases per 10 000 individuals, with reported rates ranging from 2 to 20 cases per 10 000 individuals (APA, 2000). Furthermore, autism occurs five times more often than Down's syndrome and three times more often than childhood diabetes (Nash,2002; Time Magazine,2002).
In 2003, international research showed that the occurrence of autism increased worldwide (Fombonne, 2003; Sicile-Kira, 2003; Yazbak, 2003), with a prevalence rate of autism at 34 per 10 000 and the prevalence rate of PDD at 60 per 10 000 (Fombonne, 2003). The increase of autism between the ages of 6 - 21 years in the U.S. over the last decade, was notably greater than the number of children with disabilities in general (Yazbak,2003).
In 2005, Fombonne (2005) stated the prevalence of autism as 13 per 10 000. This global estimate is derived from a conservative analysis of existing data. According to Cure Research (2005) autism affects an estimated 10 - 20 in every 10 000 individuals, depending on diagnostic criteria used.
Currently, in 2007, the prevalence of PDD is 1 per 166 (Grinker, 2007). The cause of the high prevalence of PDD is debatable. The prevalence of autism could be an underestimation,as children with milder or high-functioning autism are likely to have been missed;an exaggeration, as the increase of autism could be due to a broadening of the diagnostic criteria, public awareness, worldwide introduction of the WHO (1992) and the APA (2000) diagnostic criteria since the early 1990s, or due to a
genuine increase in incidences of autism (Baird et al., 2006; Kurita, 2006; Pulse, 2006; Wikipedia, 2007b; Grinker, 2007). Similar to the above divergence of opinions, opinion in South Africa is not unanimous regarding autism's prevalence.
2.5.2 Gender prevalence
Consistent research from as early as the 1970' s to date has proven that there is a higher rate of autism and its spectrum disorders in males than females (Wing, 1971;
1980; Furneaux and Roberts, 1977; Wing, 1993; APA, 2000; Kaminsky and Dewey, 2002; Opleidscentrum Autisme,2004; Cure Research, 2005; Volkmar and K1in,2005;
Grinker, 2007). Several researchers are of the opinion that autism itself occurs in 4 times as many boys as girls (Sici1e-Kira,2003; Opleidscentrum Autisme, 2004; Cure Research, 2005),while the APA (2000) states that the rates are 4 to 5 times higher in males than in females. Other researchers believe that the rates rise as high as 6 to 1 (Kaminsky and Dewey,2001).
Researchers believe that autism could have a slightly different presentation in females and that this could lead to a wrong diagnosis in some female cases, it often being diagnosed as mental retardation (APA, 2000). Girls in general may develop better language and social skills than boys,and their interest patterns are also not usually as restricted and technical as those of boys. They therefore do not show evidence of typical 'autism quality'. On the other hand,these girls may be incorrectly diagnosed with other problems like 'social deficits and leaming problems' ; girls who refuse to do something may often be diagnosed with "pathological demand avoidance". Girls who will only talk in front of certain people,but are mute or almost mute when with other people, may be diagnosed as atypical variants of "selective mutism" (Peeters and Gillberg,1999:40).
2.5.3 Prevalence in race, ethnic and socio-economic groups
According to several researchers,autism does not affect any specific race, ethnic or socialgroup. Autism has nothing to dowith familyincome,lifestyleand educational
levels of parents (Peeters and Gillberg, 1999; Autism Society of America, 2000;
Nash, 2002; Dyches et al., 2004;Eaton, 2005; Volkmar and KEn,2005; Fombonne, 2005;Kurita, 2006;Grinker, 2007).
Most epidemiological studies have been conducted in Western countries and cannot be generalized to other countries, such as developing nations. This could be due to the fact that some families from minority cultures do not want to participate because of language barriers, mistrust, fear, or misunderstanding. It could also be that, to avoid stigma, families from some cultural or socio-economic groups advocate a diagnosis of autism rather than mental retardation. Some cultures do not consider certain behaviours of children with autism as problematic but rather as part of their culture e.g. avoiding eye contact, aggressive behaviours - resulting in the child not being taken to a doctor.
The prevalence of autism has increased dramatically, which makes it necessary to explore possible causal factors of autism,thereby facilitating prevention and support.