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.



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 interventionssuch 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 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.




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.




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.




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.




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.




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.”



Most patients presenting in clinical settings with an Autism Spectrum Disorder, such as Aspergers syndrome or autism, have other comorbid disorders. Mental retardation is a possible comorbid disorder at the more severe end of the autism spectrum.


Mental retardation is a term for a pattern of persistently slow learning of basic motor and language skills (“milestones”) during childhood, and a significantly below-normal global intellectual capacity as an adult. One common criterion for diagnosis of mental retardation is a tested intelligence quotient (IQ) of 70 or below.


People with mental retardation may be described as having developmental disabilities, global developmental delay, or learning difficulties.



The term “Mental retardation” has acquired pejorative and shameful connotations over the last few decades and is now used almost exclusively in technical or scientific contexts where exactness is necessary. The term ‘intellectual disability’ is increasingly common, and used on this website where possible.


In North America the broad term developmental delay has become an increasingly preferred synonym by many parents and direct support professionals. Elsewhere, however, developmental delay is generally used to imply that appropriate intervention will improve or completely eliminate the condition, allowing for “catching up.” Importantly, this term carries the emotionally powerful idea that the individual’s current difficulties are likely to be temporary.
Developmental disability is preferred by most physicians, but can also refer to any other physical or psychiatric delay, such as delayed puberty.
Both the phrases ‘intellectual disability’ and ‘learning disability’ are increasingly being used as a synonym for people with significantly below-average IQ. These terms are sometimes used as a means of separating general intellectual limitations from specific, limited deficits as well as indicating that it is not an emotional or psychological disability. Intellectual disability is also used to describe the outcome of traumatic brain injury or lead poisoning or dementing conditions such as Alzheimer’s disease. It is not specific to congenital conditions like Down syndrome.


The American Association on Mental Retardation continues to use the term mental retardation. In June 2006 its members voted to change the name of the organization to the “American Association on Intellectual and Developmental Disabilities,” rejecting the options to become the AAID or AADD. Part of the rationale for the double name was that many of the members worked with people with autism and Asperger’s syndrome, also known as pervasive developmental disorders, not all of whom were also mentally retarded.


In the UK, “mental handicap” had become the common medical term, replacing “mental subnormality” in Scotland and “mental deficiency” in England and Wales, until Stephen Dorrell, Secretary of State for Health in England and Wales from 1995-7, changed the National Health Service’s designation to “learning disability.” The new term is not yet widely understood, and is often taken to refer to problems affecting schoolwork (the American usage): which are known in the UK as “learning difficulties.” British social workers may use “learning difficulty” to refer to both people with MR and those with conditions such as dyslexia.



There are many signs. For example, children with developmental disabilities may learn to sit up, to crawl, or to walk later than other children, or they may learn to talk later. Both adults and children with intellectual disabilities may also:

• have trouble speaking
• find it hard to remember things
• have trouble understanding social rules
• have trouble discerning cause and effect
• have trouble solving problems
• have trouble thinking logically.


In early childhood mild disability (IQ 60–70) may not be obvious, and may not be diagnosed until they begin school. Even when poor academic performance is recognized, it may take expert assessment to distinguish mild mental disability from learning disability or behavior problems. As they become adults, many people can live independently and may be considered by others in their community as “slow” rather than retarded.


Moderate disability (IQ 50–60) is nearly always obvious within the first years of life. These people will encounter difficulty in school, at home, and in the community. In many cases they will need to join special, usually separate, classes in school, but they can still progress to become functioning members of society. As adults they may live with their parents, in a supportive group home, or even semi-independently with significant supportive services to help them, for example, manage their finances.


Among people with intellectual disabilities, only about one in eight will score below 50 on IQ tests. A person with a more severe disability will need more intensive support and supervision his or her entire life.


The limitations of cognitive function will cause a child to learn and develop more slowly than a typical child. Children may take longer to learn to speak, walk, and take care of their personal needs such as dressing or eating. Learning will take them longer, require more repetition, and there may be some things they cannot learn. The extent of the limits of learning is a function of the severity of the disability.


Nevertheless, virtually every child is able to learn, develop, and grow to some extent.



According to the DSM-IV, there are three criteria before a person is considered to have a developmental disability: an IQ below 70, significant limitations in two or more areas of adaptive behavior (i.e., ability to function at age level in an ordinary environment), and evidence that the limitations became apparent in childhood. It is formally diagnosed by professional assessment of intelligence and adaptive behavior.


IQ tests were created as an attempt to measure a person’s abilities in several areas, including language, numeracy and problem-solving. The average score is 100. People with a score below 75 will often, but not always, have difficulties with daily living skills. Since factors other than mental ability (depressionanxiety, lack of adequate effort, etc.) can yield low IQ scores, it is important for the evaluator to rule them out prior to concluding that measured IQ is “significantly below average”.


The following ranges, based on the Wechsler Adult Intelligence Scale (WAIS), are in standard use today:
Class IQ
Profound mental retardation Below 20
Severe mental retardation 20–34
Moderate mental retardation 35–49
Mild mental retardation 50–69
Borderline mental retardation 70–79


Significant limitations in two or more areas of adaptive behavior

Adaptive behavior, or adaptive functioning, refers to the skills needed to live independently (or at the minimally acceptable level for age). To assess adaptive behavior, professionals compare the functional abilities of a child to those of other children of similar age. To measure adaptive behavior, professionals use structured interviews, with which they systematically elicit information about the person’s functioning in the community from someone who knows them well. There are many adaptive behavior scales, and accurate assessment of the quality of someone’s adaptive behavior requires clinical judgment as well. Certain skills are important to adaptive behavior, such as:

• daily living skills, such as getting dressed, using the bathroom, and feeding oneself
• communication skills, such as understanding what is said and being able to answer
• social skills with peers, family members, spouses, adults, and others.


Evidence that the limitations became apparent in childhood

This third condition is used to distinguish it from dementing conditions such as Alzheimer’s disease or is due to traumatic injuries that damaged the brain.



Down syndrome, fetal alcohol syndrome and Fragile X syndrome are the three most common inborn causes. However, doctors have found many other causes. The most common are:


Genetic conditions. Sometimes disability is caused by abnormal genes inherited from parents, errors when genes combine, or other reasons. Examples of genetic conditions include Down syndrome,Fragile X syndrome, and phenylketonuria (PKU).
Problems during pregnancy. Mental disability can result when the fetus does not develop inside the mother properly. For example, there may be a problem with the way the fetus’s cells divide as it grows. A woman who drinks alcohol (see fetal alcohol syndrome) or gets an infection like rubella during pregnancy may also have a baby with mental disability.


Problems at birth. If a baby has problems during labor and birth, such as not getting enough oxygen, he or she may have developmental disability due to brain damage.


Health problems. Diseases like whooping cough, measles, or meningitis can cause mental disability. It can also be caused by not getting enough medical care, or by being exposed to poisons like lead or mercury.


Iodine deficiency, affecting approximately 2 billion people worldwide, is the leading preventable cause of mental disability in areas of the developing world where iodine deficiency is endemic. Iodine deficiency also causes goiter, an enlargement of the thyroid gland. More common than full fledged cretinism, as retardation caused by severe iodine deficiency is called, is mild impairment of intelligence. Certain areas of the world due to natural deficiency and governmental inaction are severely affected. India is the most outstanding, with 500 million suffering from deficiency, 54 million from goiter, and 2 million from cretinism. Among other nations affected by iodine deficiency, China and Kazakhstan have begun taking action, while Russia has not.


Malnutrition is a common cause of reduced intelligence in parts of the world affected by famine such as Ethiopia.


The use of forceps during birth can lead to intellectual disability in an otherwise normal child. They can fracture the skull and cause brain damage.


Institutionalization at a young age can cause intellectual disability in normal children.


Sensory deprivation in the form of severe environmental restrictions (such as being locked in a basement), prolonged isolation, or severe atypical parent-child interactions.


Psycho-social disadvantage. Contributing factors are lack of reading material, use of language not common in that community, poor diet, poor health practices, and poor housing.



By most definitions it is more accurately considered a disability rather than a disease. It can be distinguished in many ways from mental illness, such as schizophrenia or depression. Currently, there is no “cure” for an established disability, though with appropriate support and teaching, most individuals can learn to do many things.


There are usually a variety of agencies in the most countries that provide assistance for people with developmental disabilities. They will usually include state-run, for-profit, and non-profit, privately run agencies. Within one agency there could be departments that include fully staffed residential homes, day habilitation programs that approximate schools, workshops wherein people with disabilities can obtain jobs, programs that assist people with developmental disabilities in obtaining jobs in the community, programs that provide support for people with developmental disabilities who have their own apartments, programs that assist them with raising their children, and many more.


Although there is no specific medication for intellectual disability, many people with developmental disabilities have further medical complications and may take several medications. Beyond that there are specific programs that people with developmental disabilities can take part in wherein they learn basic life skills. These “goals” may take a much longer amount of time for them to accomplish, but the ultimate goal is independence. This may be anything from independence in tooth brushing to an independent residence. People with developmental disabilities learn throughout their lives and can obtain many new skills even late in life with the help of their families, caregivers, clinicians and the people who coordinate the efforts of all of these people.



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