GASTROINTESTINAL TRACT
PROBLEMS
It has been claimed that up to fifty percent
of children with autism
experience persistent gastrointestinal tract problems, ranging from
mild to moderate degrees of inflammation in both the upper and lower
intestinal tract. This has been described as a syndrome, autistic
enterocolitis, by Dr. Andrew Wakefield; this diagnostic terminology,
however, has been questioned by medical experts. Constipation,
often with overflow, or encopresis, is often associated with developmental
disorders in children, and is often difficult to resolve, especially
among those with behavioral
and communication
problems. Click here
strategies to deal with constipation.
'leaky gut' theory of autism
This high prevalence of gastrointestinal tract
problems has led some to claim this is one of the causes
of Autism. Many autistic individuals have permeable intestinal
tracts, often referred to as ‘leaky gut.’ Suggested causes for this
include viral infection such as measles, an overgrowth of yeast
(candida albicans), and a reduction in phenol sulfur transferase
which normally lines the intestinal tract. Some proponents of the
leaky gut theory also theorize that heavy metals could be a cause.
The 'leaky gut' theory proposes that some children
are unable to digest the protein in many cereals (gluten) or in
milk (casein) completely. It claims that casein and gluten proteins
aren't properly broken down and lead to a build up of opioids in
the body, leading to high pain tolerance, repetitive
behaviors and lack of concentration. A gluten and casein-free
diet is believed by some parents of autistic children to aid in
reducing symptoms of autism, Asperger's syndrome and other Autism Spectrum Disorders.
As with many aspects of Autism, there is much
research needed in this area, but there is a growing consensus that
gastrointestinal tract problems are a comorbid
disorder with autism Spectrum Disorders, not an actual cause.
Some parents claim that biomedical
interventions such as the gluten-free
casein-free diet have had varying degrees of benefit for their
child. This fact sheet covers some of the controversy around this
theory.
Autistic enterocolitis
Autistic enterocolitis is a controversial condition
first reported by British gastroenterologist Dr. Andrew Wakefield
to describe a number of common clinical symptoms and signs which
he contends is distinctive to autism. There are numerous medical
conditions comorbid to Autism Spectrum Disorders, with colitis perhaps
the most prevalent. Up to fifty percent of children with Autism Spectrum Disorders experience persistent gastrointestinal problems,
with mild to moderate degrees of inflammation in both the upper
and lower intestinal tract. The term is starting to come into wider
use as other researchers examine enterocolitis in autism.
Background to persistent gastrointestinal tract problems
Until the 1970s, autism was considered a very
rare condition, but it is diagnosed much more often nowadays, whether
due to increased diagnostic vigilance by doctors, changes of diagnostic
categories, or an actual increase
in incidence. Estimates of the percentage of late-onset autism
cases range from 20% to 80%, with the lower percentage reported
by sources including the British Medical Journal as not
having changed in recent years. Wakefield, however, contends that
a regressive syndrome "may reflect a subset of children with
developmental disorders with distinct etiological and clinical features."
Despite others describing common bowel features,
there have been no peer reviewed studies yet published, as of 2006,
corroborating the existence of autistic enterocolitis; other studies
have explicitly denied its existence. Thus, it is not generally
accepted that the types of colitis found in autism are unique to
autism. To date, no adequately controlled study has been published
comparing the gut pathology of autistic and non-autistic children.
The Lancet study
When Wakefield and his colleagues first reported
in 1998 a possible association between autistic regression, IBD,
and MMR vaccines in the Lancet, they evaluated a dozen children
with pervasive developmental disorders, apparent developmental regression,
and intestinal symptoms, referred to the Royal Free Hospital.
Onset of behavioral symptoms was linked to recent
(within two weeks) immunization with MMR vaccine in six of the children
diagnosed with autism. An autism diagnosis was not linked to MMR
vaccination, or the link was tenuous, in the remaining six. The
most consistent finding was lymphoid nodular hyperplasia of the
terminal ileum in nine of the children. This feature has also been
reported in non-autistic children. A variety of colonic and rectal
mucosal abnormalities was seen in eight cases. Biopsies of the ileum
showed reactive lymphoid follicular hyperplasia in seven. Biopsies
of the colon showed a diffuse mononuclear cell infiltrate in six.
Wakefield and his colleagues say they have described
features of regressive autism with bowel disorders, or autistic
enterocolitis, although these findings have been questioned:
* A vast majority of the children have chronic
swelling of the lymphoid tissue lining the intestines, particularly
near where the small and large intestines meet, and chronic inflammation
of the large intestine, producing abdominal pain and alternating
constipation and diarrhea.
* Affected children exhibit impaired cellular immunity to common
recall antigens; the numbers of circulating white blood cells are
low.
* A specific measles protein signal has been detected in immune
cells of inflamed lymphoid tissue; another such indication is that
affected children often have raised levels of measles-specific antibodies
in their bloodstream.
* A loss of speech and language accompanied by symptoms of excessive
thirst, bowel disturbances, self-injury, and a self-limited diet
associated with cravings for particular foods.
* Allergies, food intolerances, and recurrent upper respiratory
tract infections unresponsive to conventional treatments are also
prominent features of this sub-group.
IBD and regressive autism
Although also characterized by intestinal lymphoid
tissue disease activity, the primary symptoms and diagnostic criteria
of the syndrome are behavioral and developmental. Age, dose of infection
and the interaction of two or more viruses are claimed to be factors
leading to regressive autism. According to Wakefield, "it is
possible that the emergence of this new type of autism is related
to a different pattern of exposure to environmental triggers."
Abnormal metabolites of macro-nutriments have been found in the
urine of autistic children, suggesting an incomplete or insufficient
intra-intestinal digestion.
Potential link to MMR vaccinations
Central to one of the most acrimonious controversies
in autism, Wakefield has hypothesized that autistic enterocolitis
is an emergent IBD phenotype that follows from the increased incidence
of low-dose compound viral exposures, i.e., exposures associated
with the vast increase in the number of vaccinations given to children
during a period when their immune systems are rapidly developing.
Specifically, Wakefield asserts the autistic enterocolitis syndrome
involves increased permeation of neurotoxic substances across the
blood-brain barrier during a vulnerable part of brain development,
leading to regressive autism. Other research, however, rejects this.
Researchers have identified a high incidence of bowel symptoms in
autistic children before the MMR vaccine was licensed.
"Retraction of an interpretation"
The Lancet paper has been widely cited as an impetus
for concerns regarding the MMR vaccine being a cause of autism.
Wakefield gave interviews after the publication of the paper, including
on 60 Minutes where he raised concerns regarding administration
of the MMR vaccine. In the Lancet paper, Wakefield and his co-authors
said on the issue:
"We did not prove an association between
measles, mumps, and rubella vaccine and the syndrome described.
Virological studies are underway that may help to resolve this issue".
In 2004, ten of the authors issued a statement
in the Lancet (2004;363:750) entitled "Retraction of an interpretation".
In it the authors recommended first that work continue into their
new discovery of intestinal problems of autistic children, saying:
"The main thrust of this paper was the first
description of an unexpected intestinal lesion in the children reported.
Further evidence has been forthcoming in studies from the Royal
Free Centre for Paediatric Gastroenterology and other groups to
support and extend these findings. While much uncertainty remains
about the nature of these changes, we believe it important that
such work continues, as autistic children can potentially be helped
by recognition and treatment of gastrointestinal problems."
The authors went on to say that they retracted
the "interpretation placed upon" their findings but the
statement did not retract the findings themselves:
"We wish to make it clear that in this paper
no causal link was established between MMR vaccine and autism as
the data were insufficient. However, the possibility of such a link
was raised and consequent events have had major implications for
public health. In view of this, we consider now is the appropriate
time that we should together formally retract the interpretation
placed upon these findings in the paper, according to precedent."
Some view the decision as a means whereby the
co-authors could dissociate themselves from the implication that
there was a conclusion that there was any association at all. Others
view it as an endeavor to disassociate the primary research into
intestinal problems from the MMR/autism controversy so that original
work could continue for the benefit of autistic children. Despite
the statement the study findings still are always referenced in
studies that test the hypothesis of MMR being a cause of autism.
The editor of the Lancet and the authors were
taken aback by the furor that arose and the attention the paper
received after publication.
Just before the retraction of an interpretation,
criticism arose over the fact that the Royal Free Hospital had received
£55 000,00 in August 1996 from lawyers preparing to sue MMR manufacturers
for support of Dr. Wakefield's research. Later, Wakefield asserted
that the donation was to fund a second clinical study; some of the
children involved were subjects in both studies.
Wakefield currently faces disciplinary charges
before the General Medical Council over the conduct of his research.
In October 2005, the Cochrane Library published
its analysis of 31 "high quality" medical studies which
concluded no link could be found between the MMR vaccine and bowel
disease, autism or other pervasive developmental disorders. To increase
the rigor of the meta-analysis, the criteria of the meta-analysis
excluded smaller studies and studies that had the potential for
bias. Wakefield's work was specifically excluded in the meta-analysis
due to small sample size. With regard to the vaccine, Cochrane said
that its survey of research "strongly supports its use."
Click here
for the full range of Asperger's and autism fact sheets at www.autism-help.org
Click here
to read the Allergies and Food Sensitivities fact sheet
Click here
to read the Brain chemistry and autism fact sheet
This autism fact sheet is licensed under the
GNU
Free Documentation. It is derivative of an autism and Asperger's
syndrome-related articles at http://en.wikipedia.org |
