Controversies in autism
Encyclopedia
Controversies in autism encompass the disagreement over the exact nature of autism
, its causes
and manifestations. Autism is considered to be a neurodevelopmental condition which manifests itself in markedly abnormal social interaction, communication ability, and patterns of interests.
The cause(s) of autism and the spectrum
of pervasive developmental disorder
s (PDDs) are either unknown or unclear.
estimate a prevalence
of one to two cases per 1,000 people for autism
, and about six per 1,000 for ASD; because of inadequate data, these numbers may underestimate ASD's true prevalence. ASD averages a 4.3:1 male-to-female ratio. The number of children known to have autism has increased dramatically since the 1980s, at least partly due to changes in diagnostic practice; it is unclear whether prevalence has actually increased; and as-yet-unidentified environmental risk factors cannot be ruled out. The risk of autism is associated with several prenatal factors, including advanced parental age and diabetes in the mother during pregnancy. ASD is associated with several genetic disorder
s and with epilepsy, and autism is associated with mental retardation
.
s. One as yet unproven theory is that there may be genes which contribute to a vulnerability to environmental triggers or have another role in the etiology of autism.
Genetics is viewed as an underlying factor. However, while some parents of those with autism are progressively also being diagnosed on the autism spectrum, at least some autistic children have apparently neurotypical
parents. This suggests to some that genetics are either not a necessary cause or that they don't play a part in all cases of ASD, although it could also mean that the gene(s) responsible may be recessive or a spontaneous mutation
. The spectrum of autistic disorders is notable for its significant gender
disparity, with the incidence of autism in males greatly exceeding the incidence in females. Whilst this could be evidence for a genetic theory, it has also been argued that male brains may be more vulnerable during early development.
and vaccinations, leading notably to the MMR vaccine controversy
, the thiomersal controversy
, and the theory of vaccine overload.
(AAP) asked vaccine makers to remove the organomercury
compound thiomersal
(spelled "thimerosal" in the U.S.) from vaccines as quickly as possible, and thiomersal has been phased out of U.S. and European vaccines, except for some preparations of influenza vaccine. The CDC and the AAP followed the precautionary principle
, which assumes that there is no harm in exercising caution even if it later turns out to be unwarranted, but their 1999 action sparked confusion and controversy that has diverted attention and resources away from efforts to determine the causes of autism. Since 2000, the thiomersal in child vaccines has been alleged to contribute to autism
, and thousands of parents in the United States have pursued legal compensation from a federal fund. A 2004 Institute of Medicine
(IOM) committee favored rejecting any causal relationship between thiomersal-containing vaccines and autism. Autism incidence rates increased steadily even after thiomersal was removed from childhood vaccines. Currently there is no accepted scientific evidence that exposure to thiomersal is a factor in causing autism.
was the subject of controversy after publication in The Lancet
of a 1998 paper by Andrew Wakefield
, et al., reporting a study of 12 children mostly with autism spectrum disorders with onset soon after administration of the vaccine. During a 1998 press conference, Wakefield suggested that giving children the vaccines in three separate doses would be safer than a single vaccination. This suggestion was not supported by the paper, and several subsequent peer-reviewed studies have failed to show any association between the vaccine and autism. It later emerged that Wakefield had received funding from litigants against vaccine manufacturers and that Wakefield had not informed colleagues or medical authorities of his conflict of interest
; had this been known, publication in The Lancet would not have taken place in the way that it did. Wakefield has been heavily criticized on scientific grounds and for triggering a decline in vaccination rates, as well as on ethical grounds for the way the research was conducted. In 2004 the MMR-and-autism interpretation of the paper was formally retracted by 10 of Wakefield's 12 co-authors, and in 2010 The Lancets editors fully retracted the paper.
The CDC, the IOM of the National Academy of Sciences
, and the UK National Health Service
have all concluded that there is no evidence of a link between the MMR vaccine and autism. In 2009, The Sunday Times
reported that Wakefield had manipulated patient data and misreported results in his 1998 paper, creating the appearance of a link with autism. A 2011 article in the British Medical Journal
described how the data in the study had been falsified by Wakefield so it would arrive at a predetermined conclusion. An accompanying editorial in the same journal described Wakefield's work as an "elaborate fraud" which led to lower vaccination rates, putting hundreds of thousands of children at risk and diverting energy and money away from research into the true cause of autism.
A 2007 study suggested that Raven's Progressive Matrices
(RPM), a test of abstract reasoning, may be a better indicator of intelligence for autistic children than the more commonly used Wechsler Intelligence Scale for Children
(WISC). Researchers suspected that the WISC relied too heavily on language to be an accurate measure of intelligence for autistic individuals. The neurotypical children scored similarly on both tests, but the autistic children fared far better on the RPM than on the WISC. The RPM measures abstract, general and fluid reasoning, an ability autistic individuals have been presumed to lack. A 2008 study found a similar effect, but to a much lesser degree and only for individuals with Wechsler IQs less than 85.
A 2006 review questioned the common assumption that most children with autism are mentally retarded.
is relatively absent or atypical. These joint attention skills seem to be prerequisites for functional language development. It has also been hypothesized that autistic children initiate joint attention perhaps even as often as their neurotypical peers, albeit in atypical ways, and that a parent should join an autistic child's focus of attention and try harder to notice the child's atypical requests for attention rather than insist on typical behavior from the child. The empirical data supporting the latter hypothesis has been questioned.
Autism
Autism is a disorder of neural development characterized by impaired social interaction and communication, and by restricted and repetitive behavior. These signs all begin before a child is three years old. Autism affects information processing in the brain by altering how nerve cells and their...
, its causes
Causes of autism
Many causes of autism have been proposed, but understanding of the theory of causation of autism and the other autism spectrum disorders is incomplete. Heritability contributes about 90% of the risk of a child developing autism, but the heritability of autism is complex and typically it is...
and manifestations. Autism is considered to be a neurodevelopmental condition which manifests itself in markedly abnormal social interaction, communication ability, and patterns of interests.
The cause(s) of autism and the spectrum
Spectrum disorder
A spectrum in psychiatry is a range of linked conditions, such that there is "not a unitary disorder but rather a syndrome composed of subgroups". The subgroups may be linked together by clinical appearance or by shared underlying causation...
of pervasive developmental disorder
Pervasive developmental disorder
Pervasive developmental disorders is a diagnostic category refers to a group of disorders characterized by delays or impairments in communication, social behaviors, and cognitive development.Pervasive developmental disorders include Autism, Asperger's syndrome, Rett's syndrome, Childhood...
s (PDDs) are either unknown or unclear.
Epidemiology
The epidemiology of autism is the study of factors affecting autism spectrum disorders (ASD). Most recent reviews of epidemiologyEpidemiology
Epidemiology is the study of health-event, health-characteristic, or health-determinant patterns in a population. It is the cornerstone method of public health research, and helps inform policy decisions and evidence-based medicine by identifying risk factors for disease and targets for preventive...
estimate a prevalence
Prevalence
In epidemiology, the prevalence of a health-related state in a statistical population is defined as the total number of cases of the risk factor in the population at a given time, or the total number of cases in the population, divided by the number of individuals in the population...
of one to two cases per 1,000 people for autism
Autism
Autism is a disorder of neural development characterized by impaired social interaction and communication, and by restricted and repetitive behavior. These signs all begin before a child is three years old. Autism affects information processing in the brain by altering how nerve cells and their...
, and about six per 1,000 for ASD; because of inadequate data, these numbers may underestimate ASD's true prevalence. ASD averages a 4.3:1 male-to-female ratio. The number of children known to have autism has increased dramatically since the 1980s, at least partly due to changes in diagnostic practice; it is unclear whether prevalence has actually increased; and as-yet-unidentified environmental risk factors cannot be ruled out. The risk of autism is associated with several prenatal factors, including advanced parental age and diabetes in the mother during pregnancy. ASD is associated with several genetic disorder
Genetic disorder
A genetic disorder is an illness caused by abnormalities in genes or chromosomes, especially a condition that is present from before birth. Most genetic disorders are quite rare and affect one person in every several thousands or millions....
s and with epilepsy, and autism is associated with mental retardation
Mental retardation
Mental retardation is a generalized disorder appearing before adulthood, characterized by significantly impaired cognitive functioning and deficits in two or more adaptive behaviors...
.
Genetics
There is evidence that autism has a genetic component, and ongoing research focuses on finding the biomarkers that determine autistic phenotypePhenotype
A phenotype is an organism's observable characteristics or traits: such as its morphology, development, biochemical or physiological properties, behavior, and products of behavior...
s. One as yet unproven theory is that there may be genes which contribute to a vulnerability to environmental triggers or have another role in the etiology of autism.
Genetics is viewed as an underlying factor. However, while some parents of those with autism are progressively also being diagnosed on the autism spectrum, at least some autistic children have apparently neurotypical
Neurotypical
Neurotypical is a term that was coined in the autistic community as a label for people who are not on the autism spectrum: specifically, neurotypical people have neurological development and states that are consistent with what most people would perceive as normal, particularly with respect to...
parents. This suggests to some that genetics are either not a necessary cause or that they don't play a part in all cases of ASD, although it could also mean that the gene(s) responsible may be recessive or a spontaneous mutation
Mutation
In molecular biology and genetics, mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic...
. The spectrum of autistic disorders is notable for its significant gender
Gender
Gender is a range of characteristics used to distinguish between males and females, particularly in the cases of men and women and the masculine and feminine attributes assigned to them. Depending on the context, the discriminating characteristics vary from sex to social role to gender identity...
disparity, with the incidence of autism in males greatly exceeding the incidence in females. Whilst this could be evidence for a genetic theory, it has also been argued that male brains may be more vulnerable during early development.
Vaccines
Several controversial claims have been made with regard to autismAutism
Autism is a disorder of neural development characterized by impaired social interaction and communication, and by restricted and repetitive behavior. These signs all begin before a child is three years old. Autism affects information processing in the brain by altering how nerve cells and their...
and vaccinations, leading notably to the MMR vaccine controversy
MMR vaccine controversy
The MMR vaccine controversy was a case of scientific misconduct which triggered a health scare. It followed the publication in 1998 of a paper in the medical journal The Lancet which presented apparent evidence that autism spectrum disorders could be caused by the MMR vaccine, an immunization...
, the thiomersal controversy
Thiomersal controversy
The thiomersal controversy describes claims that vaccines containing the mercury-based preservative thiomersal contribute to the development of autism and other brain development disorders...
, and the theory of vaccine overload.
Vaccine overload
Vaccine overload is the notion that giving many vaccines at once may overwhelm or weaken a child's immune system and lead to adverse effects. The idea of vaccine overload is flawed, for several reasons. First, vaccines do not overwhelm the immune system; in fact, conservative estimates predict that the immune system can respond to thousands of viruses simultaneously. Furthermore, vaccines constitute only a tiny fraction of the pathogens naturally encountered by a child in a typical year and common childhood conditions such as fevers and middle ear infections pose a much greater challenge to the immune system than vaccines do. Second, studies have shown that vaccinations, and even multiple concurrent vaccinations, do not weaken the immune system or compromise overall immunity. Finally, there is no evidence of an immune-system role in autism. The lack of evidence supporting the vaccine overload hypothesis, combined with these findings directly contradicting it, have led to the conclusion that currently recommended vaccine programs do not "overload" or weaken the immune system.Thiomersal
In 1999, the Centers for Disease Control (CDC) and the American Academy of PediatricsAmerican Academy of Pediatrics
The American Academy of Pediatrics is the major professional association of pediatricians in the United States. The AAP was founded in 1930 by 35 pediatricians to address pediatric healthcare standards. It currently has 60,000 members in primary care and sub-specialist areas...
(AAP) asked vaccine makers to remove the organomercury
Organomercury
Organomercury refers to the group of organometallic compounds that contain mercury. Typically the Hg-C bond is stable toward air and moisture but sensitive to light. Important organomercury compounds are the methylmercury cation, CH3Hg+; ethylmercury cation, C2H5Hg+; dimethylmercury, 2Hg,...
compound thiomersal
Thiomersal
Thiomersal , and commonly known in the US as thimerosal, is an organomercury compound. This compound is a well established antiseptic and antifungal agent....
(spelled "thimerosal" in the U.S.) from vaccines as quickly as possible, and thiomersal has been phased out of U.S. and European vaccines, except for some preparations of influenza vaccine. The CDC and the AAP followed the precautionary principle
Precautionary principle
The precautionary principle or precautionary approach states that if an action or policy has a suspected risk of causing harm to the public or to the environment, in the absence of scientific consensus that the action or policy is harmful, the burden of proof that it is not harmful falls on those...
, which assumes that there is no harm in exercising caution even if it later turns out to be unwarranted, but their 1999 action sparked confusion and controversy that has diverted attention and resources away from efforts to determine the causes of autism. Since 2000, the thiomersal in child vaccines has been alleged to contribute to autism
Autism
Autism is a disorder of neural development characterized by impaired social interaction and communication, and by restricted and repetitive behavior. These signs all begin before a child is three years old. Autism affects information processing in the brain by altering how nerve cells and their...
, and thousands of parents in the United States have pursued legal compensation from a federal fund. A 2004 Institute of Medicine
Institute of Medicine
The Institute of Medicine is a not-for-profit, non-governmental American organization founded in 1970, under the congressional charter of the National Academy of Sciences...
(IOM) committee favored rejecting any causal relationship between thiomersal-containing vaccines and autism. Autism incidence rates increased steadily even after thiomersal was removed from childhood vaccines. Currently there is no accepted scientific evidence that exposure to thiomersal is a factor in causing autism.
MMR vaccine
In the UK, the MMR vaccineMMR vaccine
The MMR vaccine is an immunization shot against measles, mumps, and rubella . It was first developed by Maurice Hilleman while at Merck in the late 1960s....
was the subject of controversy after publication in The Lancet
The Lancet
The Lancet is a weekly peer-reviewed general medical journal. It is one of the world's best known, oldest, and most respected general medical journals...
of a 1998 paper by Andrew Wakefield
Andrew Wakefield
Andrew Wakefield is a British former surgeon and medical researcher, known as an advocate for the discredited claim that there is a link between the measles, mumps and rubella vaccine, autism and bowel disease, and for his fraudulent 1998 research paper in support of that claim.Four years after...
, et al., reporting a study of 12 children mostly with autism spectrum disorders with onset soon after administration of the vaccine. During a 1998 press conference, Wakefield suggested that giving children the vaccines in three separate doses would be safer than a single vaccination. This suggestion was not supported by the paper, and several subsequent peer-reviewed studies have failed to show any association between the vaccine and autism. It later emerged that Wakefield had received funding from litigants against vaccine manufacturers and that Wakefield had not informed colleagues or medical authorities of his conflict of interest
Conflict of interest
A conflict of interest occurs when an individual or organization is involved in multiple interests, one of which could possibly corrupt the motivation for an act in the other....
; had this been known, publication in The Lancet would not have taken place in the way that it did. Wakefield has been heavily criticized on scientific grounds and for triggering a decline in vaccination rates, as well as on ethical grounds for the way the research was conducted. In 2004 the MMR-and-autism interpretation of the paper was formally retracted by 10 of Wakefield's 12 co-authors, and in 2010 The Lancets editors fully retracted the paper.
The CDC, the IOM of the National Academy of Sciences
United States National Academy of Sciences
The National Academy of Sciences is a corporation in the United States whose members serve pro bono as "advisers to the nation on science, engineering, and medicine." As a national academy, new members of the organization are elected annually by current members, based on their distinguished and...
, and the UK National Health Service
National Health Service
The National Health Service is the shared name of three of the four publicly funded healthcare systems in the United Kingdom. They provide a comprehensive range of health services, the vast majority of which are free at the point of use to residents of the United Kingdom...
have all concluded that there is no evidence of a link between the MMR vaccine and autism. In 2009, The Sunday Times
The Sunday Times
The Sunday Times is a British Sunday newspaper.The Sunday Times may also refer to:*The Sunday Times *The Sunday Times *The Sunday Times *The Sunday Times...
reported that Wakefield had manipulated patient data and misreported results in his 1998 paper, creating the appearance of a link with autism. A 2011 article in the British Medical Journal
British Medical Journal
BMJ is a partially open-access peer-reviewed medical journal. Originally called the British Medical Journal, the title was officially shortened to BMJ in 1988. The journal is published by the BMJ Group, a wholly owned subsidiary of the British Medical Association...
described how the data in the study had been falsified by Wakefield so it would arrive at a predetermined conclusion. An accompanying editorial in the same journal described Wakefield's work as an "elaborate fraud" which led to lower vaccination rates, putting hundreds of thousands of children at risk and diverting energy and money away from research into the true cause of autism.
Intelligence
The percentage of autistic individuals who also meet criteria for mental retardation has been reported as anywhere from 25% to 70%, a wide variation illustrating the difficulty of assessing autistic intelligence. For ASD other than autism, the association with mental retardation is much weaker.A 2007 study suggested that Raven's Progressive Matrices
Raven's Progressive Matrices
Raven's Progressive Matrices are non-verbal multiple choice measures of the reasoning component of Spearman's g , which is often referred to as general intelligence. The tests were originally developed by John C. Raven in 1936...
(RPM), a test of abstract reasoning, may be a better indicator of intelligence for autistic children than the more commonly used Wechsler Intelligence Scale for Children
Wechsler Intelligence Scale for Children
The Wechsler Intelligence Scale for Children , developed by Dr. David Wechsler, is an individually administered intelligence test for children between the ages of 6 and 16 inclusive that can be completed without reading or writing...
(WISC). Researchers suspected that the WISC relied too heavily on language to be an accurate measure of intelligence for autistic individuals. The neurotypical children scored similarly on both tests, but the autistic children fared far better on the RPM than on the WISC. The RPM measures abstract, general and fluid reasoning, an ability autistic individuals have been presumed to lack. A 2008 study found a similar effect, but to a much lesser degree and only for individuals with Wechsler IQs less than 85.
A 2006 review questioned the common assumption that most children with autism are mentally retarded.
Joint attention
Joint attention refers to a cluster of behaviors in one of two classes: a child's response to someone else pointing or shifting eye gaze, and a child seeking another's attention. Many joint-attention behaviors differ in children with autism: for example, eye contactEye contact
Eye contact is a meeting of the eyes between two individuals.In human beings, eye contact is a form of nonverbal communication and is thought to have a large influence on social behavior. Coined in the early to mid-1960s, the term has come in the West to often define the act as a meaningful and...
is relatively absent or atypical. These joint attention skills seem to be prerequisites for functional language development. It has also been hypothesized that autistic children initiate joint attention perhaps even as often as their neurotypical peers, albeit in atypical ways, and that a parent should join an autistic child's focus of attention and try harder to notice the child's atypical requests for attention rather than insist on typical behavior from the child. The empirical data supporting the latter hypothesis has been questioned.