The news that the diagnosis of autism may be brought forward is primarily of importance because it may help identify children who will require specialised support. However, it is also interesting because it breaks the co-incidental temporal association that has been part of the reason the MMR vaccine-autism hypothesis gained traction. Since the behavioural cues for autism can’t be picked up well until after one year of age, parental concern about their child being different and autism diagnoses rose after administration of the MMR vaccine. This had unfortunate consequences for the perception of MMR vaccine’s safety.
Elsabbagh et al examined “brainwaves” (event-related potentials – ERPS) of babies with a familial risk of autism when presented with pictures of faces either gazing at the baby or away from the baby. Those children who went on to develop autism diagnoses had differing ERPs.
Although the evidence of fraud, failure to find epidemiological evidence to back-up Wakefield’s claims, and failure to find measles RNA that would have supported Wakefield’s work were enough to bury any scientific case for the MMR Vaccine-autism hypothesis, the fact that autism may now be diagnosed before the MMR vaccine lays a nice wreath on top.
Not all parents whose children developed autism blamed MMR vaccine, some parents were already aware of a “difference” about their child before MMR vaccine, but it is understandable how some parents would have made the connection with the vaccine. After all, it is a key part of how clinicians make connections between a drug and adverse event, and is a strong element of assessing causality (see Bradford-Hill criteria).
The causation in the MMR vaccine debacle was neatly illustrated in an article from Prescriber [Registration required] written by Paula McDonald (a former Consultant in Communicable Disease Control).
Aristotle’s concept of syllogisms, says if certain prepositions are met, something distinct will arise from necessity. However, he also noted false syllogisms (In the UK we have an entire publication devoted to generating them, called the Daily Mail). McDonald’s figure illustrates the usual example of the horse being classified as a cat, along with the example of teddy bears and MMR vaccine causing autism.
You could replace the teddy bears with Peppa the Pig, or some other Greenfieldian scare. However, it sounds more convincing with vaccines, afterall you are introducing foreign material into a healthy child (and vaccines do cause adverse events sometimes).
Convincing people a false syllogism is wrong is a lot harder, than pointing out that A could not have caused B, because B arose months before A happened. Temporal associations are how we make sense of the everyday world. We don’t blame tripping up on a kerb on the beer we were going to have in the pub later that night.
Barring a Skynet conspiracy to send Terminators with MMR vaccine back in time to cause autism, this looks like a useful point to make to parents concerned about the risk of autism with MMR vaccine. Quite what the anti-vaccination groups will do, like the UK JABS cult, is interesting. Perhaps they will move to attack other vaccines given earlier, such as meningitis C or diptheria? Alternatively, they may look to the misapplication of physics, perhaps taking comfort in the news that neutrinos may have travelled faster than light, as their comrades-in-arms the homeopaths did.
Cross posted at Left Brain, Right Brain.