by Chan Oga, HELP University College, Malaysia.
Until the 1920s, there were only a small number of diagnoses for mental disorders such as schizophrenia, dementia, manic-depressive psychosis, paranoia, senility, epilepsy and, the most popular of them all “disorder undiagnosed”. A large proportion of people with autism at that moment would have been diagnosed as “schizophrenia childhood type”. In the 1940s, an Austrian Psychiatrist Leo Kanner (1894-1981) argued that children with autism were different from schizophrenics in the sense that they do not experience delusions. He then introduced the term “infantile autism” and observed 11 patients that led to his discovery that autism was a syndrome (Grinker, 2006). Today, autism is one out of the five disorders currently categorized under Pervasive Developmental Disorders (PDDs) which means “early occurring, non-psychotic disturbances that are qualitatively deviant from normal development” (Wick-Nelson & Israel, 2009). Today, crucial features used for diagnosing autism are social, communication and imagination impairments, as well as repetitive stereotyped behaviours (Grinker, 2006).
According to a research done by Kawamura, Takahashi and Ishii (2008), autism was rare with the prevalence of only two per 10000 in the 1970s. However, according to their current study, the rate has increased to 181 per 10000, where 52.9% had average and above average IQ scores. The result of their study was compared with results from other studies in different regions, which recorded prevalence of 24- 116 per 10000. Various possibilities were discussed to justify the inconsistency of the prevalence rates which includes the use of different diagnostic methods and different populations. Kawamura and colleagues strongly believed that the methodology of epidemiology for autism should be reviewed. However, the increase in the prevalence rate of autism since three decades ago is indisputably significant.
Questions arose following the significant rise in the prevalence number of autistic children. There are four possible reasons for the reported rise in autism cases (Newson & Hovanitz, 2006; Wazana, Bresnahan & Kline, 2007 as cited in Wick-Nelson and Isreal, 2009 & Wing, 2001). Firstly, the definition of autism has been broadened over time; that it fits a larger variety of symptoms. Secondly, the increasing interest and awareness of the disorder among professionals and parents consequently increased the likeliness of autism cases being reported. Thirdly, the increased accessibility to diagnostic services contributes to the rise in rates. Fourthly, there could be real increase. Whether or not there is a real increase in the prevalence of autism, the number of children affected by this disorder is not small and it also affects the quality of life of family members, thus the root of the disorder should be investigated for intervention.
There is a nature-nurture debate in the cause of autism. Berg (2009) wrote an article titled “Autism- An Environmental Issue After All?” which discussed on the possible environmental factors of autism. Due to the prominent social symptoms in autistic people, social-psychological reasons were suggested as causes of autism such as bad parenting, early childhood trauma and stress. However, little evidence was found. The focus changed when increasing epidemiology reported that siblings had autism despite separate upbringing (Berg, 2009).
Back to investigating environmental causes of autism- heavy metals, flame retardants, insecticides, phthalates in vinyl and cosmetics, antibacterial soaps, thalidomide, valporic acid, bacterial and viral infections are also suspected of triggering autism (Berg, 2009). A research even found positive correlation between precipitation (rain or snow) with autism rate. A possible reasoning for this would be the longer period spent in front of the television, higher Vitamin D deficiency and increased exposure to household cleaners when it rained or snowed (Berg, 2009).
Then, in 1999, the use of themirosal as a preservative in vaccines was terminated when it was thought to cause autism in children (Berg, 2009). However, Offit (2008) and McNeil (2009) in separate articles wrote that there is no link between the vaccines and autism. Epidemiological studies showed no difference in rate of people exposed and not exposed to themirosal, no difference in level of mercury in blood between autistic and non-autistic children, and the rise in prevalence of autism despite the removal of themirosal from most vaccines in the US disapproves the link of vaccination to autism. Offit (2008) wrote that the vaccine’s link with autism was a speculative notion and not based on facts, advocated by desperate parents of autistic children and law firms hoping to sue the vaccine manufacturers. This caused vaccination rates to drop and death cases from measles rose in the UK (Offit, 2008). This incident opened the eyes of scientists that they “could be confronted by people who reject facts, in which evidence is at war with belief”. This also brings us to our senses that claims from the medical world should not be taken in too quickly and research should be done before falling into false claims.
Berg (2009) also wrote about the intense-world hypothesis in exploring the environmental causes of autism where the brain of an autistic is seen as overperforming rather than underperforming. The brains of autistic children grow faster than average, thus 10% larger than non-autistic children’s brain. The extra volume is made of an extra layer of the cerebral cortex called minicolumns which are responsible for basic information processing where too much of minicolumns causes sensory-overload, withdrawal, and eventually, other symptoms of autism will follow. Environmental toxicants which are mostly excitatory create an over-responsive brain. Berg (2009) believes that this hypothesis is promising as it explains the savant phenomenon where some autistic children have extraordinary mental abilities.
Overall, Berg (2009) concluded in her article that if the environment were to play a role in causing autism, a lot of factors will be involved, instead of just one.
On the other hand, there is the opinion that genetics play a role in autism. According to Cook (1998) in his journal “Genetics of Autism”, autism is influenced by strong and complex genetic factors where the strongest evidence is shown in the relatively high concordance rate between monozygotic twins compared to dizygotic twins. If a member of the family is known to have autism, the probability of another sibling of having autism is 4.5%. That probability is 90 folds the prevalence of autism in a population, which is only 0.05- 0.10% (Cook, 1998).
Initially, it was thought that autism could be caused by an autosomal recessive inheritance, according to a segregation analysis of families with more than one autistic child done by Ritvo et al. (1985). However, Pickles et al. (1995) used a latent class analysis and found that several genes act multiplicatively to lead to autism. Pickles et al. (1995) also discussed with his colleagues that it is possible that relatives who show lesser signs of autism may have autism susceptibility genes but not enough to show it as a full syndrome. Though Pickles et al. (1995) has explicitly described various aspects of genetics that show patterns of relationship between the genetic linkage and autism, no objective identification has been made yet. The full human genome is yet to be mapped out to identify the actual gene(s) responsible for autism susceptibility.
In his journal, Cook (1998) kept referring the gene(s) responsible for autism as the “autism susceptibility genes”. The word “susceptibility” means something easily influenced, harmed or damaged (Cambridge, 2003). This implies that Cook does not assume that the gene(s) carry the autism genotype, but the gene(s) merely can be influenced by environmental factors, resulting in autism behaviour. Berg (2009) also said:
“If you just had a slightly more baseline genetically determined excitatory level of activity, and you got exposed to the same level of excitatory toxins, you would probably go
over some edge sooner than if you didn’t have it.”
From the literature researched, no definite cause was identified responsible for autism. However, it could be drawn that both environmental and genetic factors probably play a hand-in-hand role in causing autism. Whereas, the degree of which symptoms of autism is exhibited by an autistic individual probably varies with the individual’s exposure to various environmental factors.
References
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Cook, E. H. (1998). Genetics of autism. Mental retardation and developmental disabilities
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Grinker, R. R. (2006) Unstrange minds: Remapping the world of autism. New York: Basic
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Kawamura, Y., Takahashi, O. & Ishii, T. (2008). Reevaluating the incidence of pervasive
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an integrated system of screening in Toyota, Japan. Psychiatry and clinical
neurosciences, 62, 152–159.
McNeil, D.G. (2009) Court finds no link between vaccines and autism. Child Health Alert, 27, 4
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Offit, P. (2009) Science under attack: vaccines and autism. BioScienc, 59, 440-441.
Wicks-Nelson. R., Israel, A. C. (2009) Pervasive developmental disorders and schizophrenia.
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Wing, L. (2001) The autistic spectrum. California: Ulysses Press.