© Mike Connor 2005.
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AUTISM – CURRENT ISSUES 39
This short paper summarises, firstly, the content of a recent BBC documentary about autism and the MMR; then refers to a study concerning hypothesised links between Crohn’s disease and MMR. No evidence was found for any such link in either case.
The third section highlights the debated pro’s and con’s of a neonatal screening device for autism based upon a blood test to examine (immune) cell composition.
Given the advance publicity about the availability of “new” evidence about MMR to be set out in a recent BBC documentary (Horizon – May 29th 2005), the programme was monitored, and the following notes are a summary of the contents.
To begin with, it was reported that there has been a recent and apparently marked increase in the number of children diagnosed with autism, and there appeared to be an implication, particularly from the parental representative, that there must be some specific cause underlying the change of incidence.
(It can be argued however – MJC – that insufficient attention was given to the view that the shift in incidence is more concerned with changes in diagnostic practices and criteria. The concept of an autistic spectrum, coupled with the greater probability of using an autistic diagnosis rather than a diagnosis of learning disability or language disability or pervasive developmental disorder, appears most likely to explain the change in the reported rates of autism. Such a view is supported by studies such as that of Jick and Kay [2003] which showed that as the rates of autistic diagnoses in the UK have gone up, these forms of differential diagnosis have gone down… ie one is not talking about more cases, but a different way of evaluating cases.)
It was further reported that the use of the MMR vaccination has been cited as a likely causal factor behind the apparent rise in the incidence of autism.
Reference was made by parents to the deterioration in their children’s behaviour and development, following earlier normal progress, observed shortly after the vaccination was given.
However, the programme did acknowledge the risk of confusing a causal link between MMR and the onset of autistic symptoms and a purely temporal link since the time at which the child may first show signs of autistic behaviours corresponds with the time when the vaccination is routinely given.
(One might suggest that
reference should also have been made to the commonly observed regression in
skills, notably language, among a significant minority of children with autism
and ASD around the middle of their second year. This phenomenon has been widely reported by parents and
clinicians and was first noted by Kanner [1943] and by a number of studies
since … such as those of Goldberg et al [2003] or Lord et al [2004. Estimates have indicated that around 20-25%
of children later diagnosed with autism experience a loss of previously
acquired language, accompanied by a loss in social interest or general
communicability, at some age between 17 and 24 months. What matters is that this phenomenon has
been observable long before the availability of the MMR vaccine.
One might also note the existence of the separate and severe condition described as childhood integrative disorder.)
The work of Dr. Andrew Wakefield was much discussed (with a reference to the original paper in The Lancet which gave rise to the concerns over MMR), and the postulated link between MMR, a form of bowel disorder, and autism was described.
Again, the issue of timing was much stressed … with significance attributed to the emergence of autistic signs and symptoms soon after the vaccination … although there was a restatement of the risk that a causal link was being made when it is simply a matter of the events happening at much the same time. A temporal correlation is not the same as a cause.
In any event, the claim has been refined and the current hypothesis is that MMR is linked to a particular type of autism … a regressive type of autism.
However, evidence was cited in the programme that autism can first be observed up to the age of three (and possibly not recognised for exactly what it is until later, when the child enters a preschool setting) and the idea of some kind of “late” autism is not new.
Regression has been a relatively commonly observed event well before the introduction of MMR, and there is evidence that the regression appears equally to involve children who have not been given the MMR vaccination.
Data were also cited that the increase in the number of autistic diagnoses predated the introduction of the MMR and, where MMR has been withdrawn, the upward rise has been maintained.
Particular reference was made to a study in Denmark involving children born between 1991 and 1998 which indicated that rates of autism and ASD were similar among those children who had received the MR vaccination and those who had not.
Meanwhile, the risk of not having children vaccinated was underlined, with reference to the possibly severe outcomes for the children of exposure to the conditions against which the MMR vaccine gives protection.
There was also the worry expressed lest not all children would receive all three of the elements of the vaccine if they were made more readily available as separate doses.
The question was then re-posed about what has “caused” the big increase in autistic diagnoses. If it is not attributable to MMR, what is behind it ?
A possible implication was that there was some kind of establishment “cover-up” or, at least, too great a reliance upon epidemiological data (ie “ you can prove anything with statistics ”).
(Or is it a matter of a strong
need to explain the autistic condition, to find some clear and tangible answer,
especially if this might prove to be linkable to some efficient means of
prevention or an effective means of intervention ?
The probability is that there is no one causal route, and that children with autism and ASD may represent linked but differentiable conditions albeit sharing the core triad characteristics; and that it may not be appropriate anyway to look for some (single) cause behind the increase in the diagnosed incidence of autism when it is actually a matter of wider criteria for such a diagnosis alongside a reduction in the use of alternative diagnostic labels.)
The programme went on to describe how the MMR claim has been refined further still, with the current suggestion that there may be a very small number of children who are damaged by MMR but in too few cases to have any impact upon epidemiological data. Such children experience bowel disorder, and the associated pain exacerbates (and confounds) the autistic-type symptoms.
However, expert evidence was cited to the effect that around 50% of cases of neurological disorder are accompanied by bowel problems.
The counter claim is that autism is associated with a particular and distinctive form of bowel disorder, including ulceration within the small bowel or enlarged lymph nodules.
It is the measles virus which is said to have the debilitating impact upon bowel functioning, and the virus has been detected in the blood.
Even microscopic residual quantities can have this impact, and it is only due to new screening techniques (PCR) that these traces of the measles virus are detectable.
However, the studies which have given rise to this kind of hypothesis have been subject to much criticism for their perceived methodological weaknesses with the conclusions drawn seen as lacking validity.
The programme concluded with the question whether there really is a sub-sample of children with autism who have a distinctive bowel condition.
(One might also ask what
precisely is the hypothesised mechanism by which the bowel condition interacts
[ via viral traces in the blood ?] with
neurological functioning.)
The review highlighted the absence of any viable existing evidence for such a type of autism.
In particular, reference was made to ongoing studies at Guy’s Hospital which have been comparing samples of children with autism and non-autistic control children in respect of the presence of the measles virus in the blood.
No differences have been identified between the autistic and non-autistic children.
On current evidence, therefore, it was concluded that there is support for the commonly-held position that there is no MMR-autism link.
On a related theme to the above, one notes the recent study by Seagroatt (2005) which has demonstrated that, since the introduction of the MMR vaccine in the UK, there has been no increase in the occurrence of Crohn’s disease (a form of inflammatory bowel disease).
As with the controversy surrounding autism, there has been speculation that the MMR vaccine could increase the risk of Crohn’s disease, albeit with little systematic investigation of such an association.
Seagrott correlated records of MMR vaccine usage with recorded instances of this form of bowel condition during the period 1991 and 2002; and she found no evidence that Crohn’s disease showed any increase with the use of the vaccine.
Her conclusion was that strong evidence could be cited against the hypothesis of an association between this condition and the MMR vaccine, and that there is support for the view that the MMR vaccine is safe (and no less safe in this respect than the single measles vaccine).
(Summary contained in Reuters Health Information- May 12th 2005; original article in BMJ 330 1120-1121)
Reports in the national press (Sample 2005 Move towards autism test at birth raises fears. Guardian 17th May) have described how the availability of a screening for autism among neonates is becoming a more realistic prospect.
A study at the University of California has indicated that there may be scope for an early diagnostic marker within the observation of the functioning of children’s immune systems, and the concentration of certain types of cells, as reflected in blood tests.
However, at least one school of thought regards such a possibility as potentially hazardous as much as helpful. The question is raised over what precise actions could be taken in the case of newly born infants, and whether a positive diagnosis might simply cause stress and distress to the parents.
It is acknowledged that existing assessment methodology may not be very meaningful until the child is into his or her third year given the reliance upon behavioural observation.
On the one hand, the value of a much earlier assessment will reflect the usefulness of interventions available for such young children; but, on the other hand, it is argued that any delay in identifying autism reduces the opportunity for intervention during a period of very rapid brain growth and development (and potential plasticity ?). A sensitive and accurate biological marker could, it is suggested by researchers at California University, provide opportunities for understanding the nature of the condition and for introducing treatments.
The problem is that there is little evidence that existing (formal) strategies designed to help children of two years or younger are of much benefit; and reference has also been made to the anxiety, and possible interference with normal parenting practices, in the case of false-positive early diagnoses. Nevertheless, a representative of the NAS has suggested that knowing that their child has some kind of predisposition to autism could only help parents, and the children would benefit from enhanced encouragement towards shared communication and shared problem-solving activities.
In any event, even if some differences in the composition of the blood can be detected between children who are autistic and control children, it is noted that any availability of a neonatal screening device is a long way off. One next step is to determine whether the children with autism can be differentiated in this way from children with other pervasive developmental disorders; a further investigation will concern whether or not these “markers” are consistently present among all the cases of babies who go on to be formally diagnosed as autistic.
© Mike Connor 2005.
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