Autism is one of those conditions which was virtually unheard of 60 years ago but modern diagnostic criteria now classify 1 in 45 in the Western world, as autistic. Contrast this figure with the incidence recognised in the 1970s, of 1 in 2,000. Could it be that the condition has become easier and more efficiently diagnosed? Perhaps we have broadened the range of behaviours that are included? Could it be down to zealous clinicians over-diagnosing the condition? Perhaps the real incidence of autism is increasing by causes and agents, unknown?
I’ll come back to this vexed question later. Terminology for autism has changed quite recently. Autism and Asperger syndrome are lumped into the inclusive ‘Autistic Spectrum Disorder’, or ASD. The interesting part of the terminology is the spectrum bit. It implies that a wide set of disparate/ desperate clinical criteria are involved. And we are not to be disappointed. Thus a child with profound intellectual deficit with no or very little speech can be easily inserted into the spectrum. So can a child with a high IQ. In this case, the gifted child will have accompanying social interaction problems together with obsessive repetitive behaviours. What a curious condition autism has become. To my mind, these two quite different clinical presentations represent two completely separate entities. Of course, if you insert the word, ‘spectrum’ this solves the apparent incongruity, or does it? Clever physicians are apt to call this sort of thing, ‘Clinical heterogeneity’, but they would say that, wouldn't they?
From a genetic perspective, ASD is representative of a ‘multifactorial disorder’. Classically this describes a condition where several/many genes are involved. Although the cynically minded might contend that it represents a technical term for: ‘we have no bloody idea’. Regardless, there is no doubt that genetics plays a major role in the development of autism. Like the clinical classification, the genetics is considered heterogeneous. Furthermore, an ‘environmental trigger’ may be required in certain instances. Evidence indicates that in a minority of cases, the environment is paramount in eliciting the condition, especially during pregnancy. Autism mediated through environmental factors does not necessarily rule out the involvement of some form of genetic predisposing factor(s).
So why is ASD so common nowadays in comparison to the recent past and is the increase 'real' or just a matter of semantics? As mentioned, the diagnostic criteria have undergone extensive rework recently and there seems little doubt that it has become more inclusive. Children and adults who were previously diagnosed with developmental delay or intellectual retardation are now considered part of the autistic spectrum. That said, the change in diagnosis cannot explain all of the increase in reported cases. When we look at the 'incidence plot' since 1975 to date we see something very interesting. The incidence does not show a smooth linear increase. What we observe is an exponential increase. In other words, the rate of increase is accelerating over time. If this rate is maintained the incidence of autism will become 50% by 2020. And there are doom-laden sayers who predict such a scenario. Of course, because the incidence exhibits an exponential rise currently it is not necessarily the case that this rate of increase will continue. Sensible clinicians and scientists predict a plateau.
Environmental factors may be at play although experts get increasingly vague when asked to cite these factors. It has been noted that premature babies are at a higher risk of autism. Today, in the First World at least, the survival rate for premature babies has increased dramatically. However, this influence would only account for a relatively small number of newly diagnosed cases. It is speculated that older parents may be to blame. Certainly, in the West, we are seeing a skewed parenthood demographic. Sensible folk are delaying parenthood possibly due to career choices and career pressures. A whole host of agents have been considered, such as the rise of the internet, GMO, pesticides, and vaccines. Graphs are readily produced showing a correlation between a given substance and the increase in autism. But correlation is not causation and for the most part, we are totally ignorant to why autism is on the apparent rise.
One thing is sure, vaccines do not cause autism, no matter how many undereducated celebs say yea. The fraudulent work by Dr. Wakefield, suggesting a link, has been thoroughly discredited. I'll cover this distressing story in a future post. Sadly, there are folk out there who take note of deluded celebs and bestow a verity to their ramblings which they do not deserve. The celebs in question are not qualified medics or scientists and they have not critically scrutinised the peer-reviewed literature on the subject. Thus the weight of their pontifications should count as chaff and add no mass to the debate in question. But their baleful influence on the gullible general public has been profound and has resulted in the increase of serious diseases in Western countries. For this, they must bear the burden of blame.