What is Autism?

Autism is not a single disease entity. It is part of a range of developmental disorders known as autistic spectrum disorders (ASD). They begin in childhood and last through adulthood.

There is currently no cure for ASD. Treatment these days includes a wide range of specialist education and behavioural programmes that can help improve symptoms.

Symptoms of autism

ASD has a wide variety of manifestations. These can be categorized into three broad groups.

  1. Problems with social interactions. The affected children may have difficulty understanding the emotions and feelings of others
  2. Problems with language and communication skills – This may manifest as delayed language development and difficulty in starting conversations
  3. Unusual behaviors and patterns of thoughts – this could include repetitive movements and activities and the child getting upset if routines are altered.

Incidence of autism

In England it is estimated that 1 in every 100 children has an ASD. According to the Centers for Disease Control and Prevention (CDC). ASDs occur in all racial, ethnic, and socioeconomic groups, but are almost five times more common among boys than among girls. CDC estimates that about 1 in 88 children is identified with an autism spectrum disorder (ASD).

Over the last two decades the number of cases of autism are seemingly on the rise. This may not mean that the condition is becoming more widespread. Some experts argue that the rise in diagnosed cases may be due to health professionals getting better at diagnosing cases correctly. Earlier children with autism would be missed commonly and they were merely labelled “painfully shy” or “slow”.

Autism myths

Autism has also been linked to administration of the MMR vaccine (against Measles, Mumps and Rubella). Extensive studies have disproved this myth. In 2009, the National Autism Society, released a statement supporting the claim that there is no link between MMR and ASD.

Yet another myth existed that a compound containing mercury called thiomersal, which is used as a preservative in some vaccines could be linked to ASD. Thiomersal has been extensively studied and no evidence of a link to ASD has been found. Furthermore, thiomersal was removed from vaccines in the US after 1999, yet the rates of ASD have continued to rise.

Types of ASD

Being a range of disorders autism includes a wide variety of disorders of varying severity. Some of the types of ASD include:

  • Autistic disorder, sometimes known as "classic autism". This manifests as significant language delays, social and communication challenges, and unusual behaviors. There may be additional intellectual disability as well.
  • Asperger syndrome – Symptoms are milder than classic autism. There are social challenges and unusual behaviors. There may be typically no language problems or intellectual disability.
  • Pervasive developmental disorder – not otherwise specified (PDD-NOS), also known as "atypical autism" – these individuals meet some of the criteria for autistic disorder or Asperger syndrome, but not all. Symptoms may be fewer and milder. There may be social and communication challenges.

Other disorders

Children with ASD may concomitantly also have other problems such as attention deficit hyperactivity disorder (ADHD), Tourette's syndrome or other tic disorders, dyspraxia (developmental co-ordination disorder), epilepsies etc.

Prognosis or outcome of ASD

Those with mild to moderate impairments who have average or above-average intelligence often grow up to be independent adults with jobs, long-term relationships and children. However, those with below-average intelligence are likely to find it difficult to live independently as adults and may need additional care and assistance.

Autism Causes

Autism is a spectrum or range of disorders and no exact cause is known. There are several interacting causes that may lead to Autism Spectrum Disorders (ASD). In most cases there is a combination of genetic risk factors that can interact with environmental risk factors. Because of the complexity of the disorder and because of the overlapping of symptoms making each autistic individual unique, the exact cause is difficult to determine.

Genes and environment

There are several identified susceptibility genes that raise the risk of autism. Many genes likely contribute to autism. These specific genes are believed to interact with certain environmental factors. Exposure to environmental agents such as infectious agents or chemical agents (including medications and environmental toxins) during pregnancy can cause autism.

About 10-15% of cases have a specific, identifiable genetic cause and other congenital disorders, such as such as Fragile X Syndrome, Tuberous Sclerosis, and Angelman’s Syndrome. The role of the immune system in causation of autism is also gaining importance. It is, however, clear from research that autism is not caused by bad parenting.

Genetic factors

Much evidence supports the idea that genetic factors could contribute to a risk of autism. Current evidence suggests that as many as 12 or more genes on different chromosomes may be involved in autism. Each of these are involved in various degrees. Some genes may place a person at greater risk for autism, called susceptibility while yet others may cause specific symptoms or determine severity of the symptoms. Some genes with changes or mutations might add to the symptoms of autism.

The idea of genes being responsible for autism gains support from the facts like identical twins have a high risk of having ASD (36-95% of the time). In non-identical twins, if one child has an ASD, then the other is affected about 0-31% of the time. In addition, parents who have a child with an ASD have a 2%–18% chance of having a second child who is also affected.

Some other genetic conditions also raise the risk of autism. Around 10% of autistic children also have other genetic conditions such as Fragile X syndrome, Tuberous sclerosis, Down’s syndrome and other chromosomal disorders.

HOXA1, of autosomal recessive inheritance is only one of many genes involved in the spectrum of autism disorders. There may be involvement of the DbetaH (DBH) gene as well. These children have a low level of serum dopamine β-hydroxylase, which catalyzes the conversion of dopamine to norepinephrine.

Other suspected genes include NLGN3, NLGN4, NRXN1, MeCP2 etc. The Fragile X gene is associated with autism disorders and there is a positive association of the FMR-1 gene with autism. Mutations or changes in the SHANK2 synaptic scaffolding gene have been documented in autism. In addition, the Reelin gene has been associated with autism. This gene helps in lamination of the brain during the fetal life and helps in cell signalling in adult life.

Viruses and infections

Research has also shown that environmental factors, such as viruses, may also play a role in causing autism. Infections that appear to be causally related to the development of autism include encephalitis caused by measles, congenital rubella, herpes simplex virus, mumps, varicella, cytomegalovirus, and Stealth virus.

Rubella virus was the first known cause of autism. It was found later that measles and mumps viruses can cause encephalitis that can result in autism later. The infections may usually affect the fetus while in the mother’s womb.

Vaccines and autism

To date, there is no conclusive scientific evidence that any part of a vaccine or any combination of vaccines causes autism. There is also no proof that any material used to make or preserve vaccines plays a role in causing autism. This follows the fears that a vaccine preservative Thimerosal is responsible for autism.


When taken during pregnancy, the prescription drugs valproic acid and thalidomide have been linked with a higher risk of ASDs. Injury with thalidomide occurs early in pregnancy (within 20 to 24 days of conception). Misoprostol, a prostaglandin analogue used for prevention of gastric ulcers and to cause abortions is also implicated. Valproic acid given to epileptic patients may also raise the risk of autism when given in pregnant epileptic mothers.

Acetaminophen has also been suggested to cause autism. Children who were given acetaminophen after the MMR (Measles mumps and rubella) vaccine have been seen to be more likely to become autistic than children given ibuprofen.

Prematurity and other disorders

A small number of children who are born prematurely or with low birth weight may be at a greater risk for ASDs. Around 35% of individuals with autism have other disorders like depression, bipolar affective disorder, schizophrenia, schizoaffective disorder, Tourette syndrome, tics, Pica, epilepsy, hypothyroidism (underactive thyroid function), Down’s syndrome, and high blood pressure.

There may be metabolic disorders like phenylketonuria (PKU) or histidinemia, the Landau-Kleffner and Rett syndromes and a variety of other conditions that affect brain development and function.

Genetic syndromes like Fragile X syndrome, Angelman’s syndrome, Down, Edwards, and Klinefelter syndromes associated with XXY genotype and may raise the risk of autism according to some studies.

Classical mitochondrial diseases occur in some autistic individuals.  Mitochondrial dysfunction is thought to be caused by environmental toxins and could be related to autism.


It is possible that autism results from more than one cause. While defective genes may play an important role, the manifestations and severity of the condition often depends on other factors. Some of these could be the advancing age of the parents, and inflammation of the brain, defective immune systems and responses, immune response of the mother to a viral or bacterial infection, a premature birth, encephalitis in the child after birth, or environmental toxins.

Autism Mechanism

Autism is a spectrum of disorders with no specific only cause. This is the reason why its mechanism of pathophysiology is difficult to understand.

In addition to its complexity, no two individuals with autism are the same. Autism is a lifelong neurodevelopmental disorder. There is disorder of brain development. While a genetic basis is recognised, the pathophysiology of autism is unknown.

Brain studies

Brain scans using FMRI have shown abnormalities in the amygdala, hippocampus, septum, mamillary bodies, and the cerebellum of the brain. This suggests that autistic symptoms may be a consequence of abnormal function in these structures.

Autistic brains are slightly larger and heavier. Just after birth, the brain of an autistic child grows faster than usual, followed by normal or relatively slower growth in childhood. The early overgrowth seems to be most prominent in areas underlying the development of higher cognitive specialization. This may lead to disturbed neuronal migration during early gestation and a imbalance between excitatory–inhibitory networks. There may be a poorly regulated synthesis of synaptic protein. Disrupted synaptic development may also contribute to epilepsy, which may explain why the two conditions are associated.

There are excessive cells in the limbic system and they are too small. The neurons themselves seem developmentally immature. The dendritic branches appear to be truncated. Purkinje cells are affected in a widespread fashion in the cerebellum. These changes in the brain anatomy may occur at some point earlier than 30 weeks gestation (before birth).


At the subcellular level research shows that there is an elevation in a major neurotransmitter, serotonin, which affects potentiation at synapses and may play a role in the development of the nervous system.

Neurocognitive theories for autism

There are 3 neurocognitive theories of autism. These include:

  • Problems with executive functions - this means difficulties with problem solving and forward planning in order to achieve a goal. In other words acting as one’s own executive or secretary.
  • Problems with central coherence – this means failure to integrate information to form meaningful whole ideas.
  • Problems with understanding the way others think or might react to a particular situation.

Rapid shifts in attention and modulation of sensory input have been associated with the cerebellum. The under-connectivity theory of autism hypothesizes that autism is marked by under-functioning high-level neural connections and synchronization, along with an excess of low-level processes.

Autism and the immune system

Interactions between the immune system and the nervous system begin early during the embryonic stage of life, and successful neurodevelopment depends on a balanced immune response. Disturbed immune activity during critical periods of neurodevelopment is part of the mechanism of some forms of ASD. However, as autoantibodies are found in conditions other than ASD, and are not always present in ASD, the relationship between immune disturbances and autism remains unclear.

Autism Classification

Autism is part of the five pervasive developmental disorders (PDD). These are characterized by:

  • abnormalities of social interactions and communication
  • restricted interests
  • highly repetitive behavior

Autism has a wide range of severity and symptoms that is often used to classify the Autism Spectrum disorders. Each of the syndromes under ASD is different from the other. For example, people with Asperger syndrome have no substantial delay in language development.

Autism itself is often called ''autistic disorder'', ''childhood autism'', or ''infantile autism''. In some individuals autism may be silent or manifest only as a mental disability while in others there are repetitive movements like hand flapping and rocking.

Some autistic individuals may be normal in all factors of life except for being awkward socially. They may have narrowly focused interests, and verbose, pedantic communication. Boundaries between diagnostic categories are necessarily somewhat arbitrary because of the overlapping and myriad of features.

Autism diagnosis

Autism can normally be diagnosed in children at around the age of two. However, it can be difficult to diagnose as the symptoms will often only become more noticeable as they get older. Some people with ASD grow up without ever being diagnosed.

Types of ASD

Being a range of disorders autism includes a wide variety of disorders of varying severity. Some of the types of ASD include:

  • Autistic disorder, sometimes known as "classic autism". This manifests as significant language delays, social and communication challenges, and unusual behaviors. There may be additional learning difficulties and below-average intelligence as well.
  • Asperger syndrome – Symptoms are milder than classic autism. There are social challenges and unusual behaviors. There may be typically no language problems or intellectual disability. However, some areas of language development may be affected. They may typically have problems with understanding humor or figures of speech. Some children have particular skills in areas that require logic, memory and creativity, such as maths, computer science and music.
  • Pervasive developmental disorder – not otherwise specified (PDD-NOS), also known as "atypical autism" – these individuals meet some of the criteria for autistic disorder or Asperger syndrome, but not all. Symptoms may be fewer and milder. There may be social and communication challenges.

Children with ASD may concomitantly also have other problems such as attention deficit hyperactivity disorder (ADHD), Tourette's syndrome or other tic disorders, dyspraxia (developmental co-ordination disorder), epilepsies etc.

Autism can also be divided into syndromal and non-syndromal autism. Syndromal autism is associated with severe or profound mental retardation or a congenital features such as tuberous sclerosis. For example, those with Asperger syndrome. Aspergers syndrome, however, is different from other autism syndromes as these individuals tend to perform better cognitively than those with autism.

Autism may also be of the regressive type. In these children (for it is seen commonly in children), the diagnosis of autism is made on the basis of loss of language or social skills, as opposed to a failure to make progress, typically from 15 to 30 months of age. This could be a specific subtype.

Other tests for autism subtypes

Apart from diagnosis of individual subtypes by interview based tests, other tests are also useful. Newer technologies such as fMRI can help identify biologically relevant subtypes that can be viewed on brain scans, to help further neurogenetic studies of autism.

Genes are being studied as well to define the subtypes of autism. For example ''Type 1 autism'' denotes rare autism cases that test positive for a mutation in the CNTNAP2 gene.

Autism Screening

Diagnosis of autism is difficult since it is a complex disorder and no two individuals with the disorder have similar manifestations. There are no medical tests like a blood test that can help diagnose the disorder. In addition, autism may be manifested as a wide range of disorders and is thus termed Autism spectrum disorders (ASD).

Diagnosis is usually made by looking at the child’s behaviour and development. Most ASDs are detected in a toddler by the time the child is 18 months or younger.  By age 2, a diagnosis by an experienced professional can be made with relative accuracy. Final diagnosis however may be reached at a much later age.

Diagnosis involves two basic steps.

Developmental Screening

This is a short test to tell if the child is learning basic skills as appropriate for his or her age or if there are any delays. Parents are asked questions or are asked to talk or play with the child while being observed by the physician. This shows how the child learns, speaks, behaves, and moves while interacting with the primary caregiver or the parent. A delay in any of these areas could be a sign of a problem. 

Developmental screening is important for all children disabilities during regular well-child doctor visits. These are usually scheduled at 9 months, 18 months, 24 or 30 months and additional screening visits if the child is at a higher risk of developmental problems due to preterm birth, low birth weight or other reasons. Common reasons include a family history of mental retardation or autism, a sibling history of the same, another coexisting condition like Fragile X syndrome, Tuberous sclerosis, Down’s syndrome or Angelman’s syndrome.

All children need to be screened specifically for ASDs during regular well-child visits. These are scheduled at 18 months and then again at 24 months. Additional screening might be needed if a child is at high risk for ASDs. This includes children with someone in the family (e.g. parent or sibling) with ASDs and those with developmental problems due to preterm birth, low birth weight.

Screening tools are designed to help identify children who might have developmental delays. They cannot make a confirmatory diagnosis. These include Ages and Stages Questionnaires (ASQ), Communication and Symbolic Behavior Scales (CSBS), Parent's Evaluation of Development Status (PEDS), Modified Checklist for Autism in Toddlers (M-CHAT) and Screening Tool for Autism in Toddlers and Young Children (STAT) etc.

Comprehensive Diagnostic Evaluation

This is the second step in diagnosis of ASD. If the doctor detects problems on initial screening they may suggest a comprehensive diagnostic evaluation. This is a more thorough review that looks at the child’s behavior and development and interviews the parents. It may also include other tests like those for hearing and vision screening, genetic testing, neurological testing, and other medical testing.

This evaluation is performed by specialists including Developmental Pediatricians (specialists who work with child development and children with special needs), Child Neurologists (who specialize in brain, spine, and nerves and related disorders of children) and Child Psychologists or Psychiatrists (who specialize in pediatric psychiatry).

Algorithm for screening and evaluation of Autism spectrum disorders:

Autism Prognosis

Autism is a complex disorder with a variety of manifestations and is thus termed Autism Spectrum Disorders or ASD. There is no known cure for this condition. Children with autism may often grow up with lack of social support systems, employment and meaningful relationships and family. Overall this leads to severe lack of self esteem. Symptoms tend to become less severe with age but with most patients with severe autism independent living is unlikely.

Prognosis or outcome of autism

  • Some children with autism may improve at 4-6 years of age especially those with mild autism who have been treated at an early age. These children who improve may be able to include themselves among their normal peers. Current policy of inclusion within the education system helps to support the majority of ASD sufferers within mainstream schools.
  • Results from surveys show that 49% of adults with autism still living with parents and only around 12% have full time employment.
  • A 2004 review of autistic adults diagnosed as autistic children with IQ above 50 in UK found that 12% autistic adults achieved a high level of independence as adults. 10% had a social life and some employment but required some support, 19% had some independence but were living at home. 46% needed specialist residential provision and 12% needed high-level hospital care.
  • In another Swedish study in 2005, it was noted that of all adults with autism only 4% achieved independence. This study included all sufferers of ASD irrespective of IQ.
  • Prognosis also depends on co-existing mental retardation. 25% to 70% of ASD sufferers may have varying degrees of mental retardation. For ASD other than autism, the association with mental retardation is much weaker.
  • With rising awareness about autism more and more parents are amenable to early screening especially of high risk children
  • It is also seen that reported cases of autism increased dramatically in the 1990s and early 2000s. This increase is largely attributable to improvements in diagnostic practices and public awareness. Other factors such as environmental toxins, advanced parental age at the time of pregnancy etc. may also be important.
  • Prognosis also depends on diseases that co-exist with autism. These include genetic disorders like Fragile X syndrome, Down’s syndrome etc. About 10–15% of autism cases have an identifiable chromosomal abnormality.

Autism Management

Autism has no cure at present. Autism spectrum disorder (ASD) is a complex disorder with various manifestations. The aim of treatment is to lessen associated difficulties and deficits and to improve quality of life and functional independence. No single treatment is best and management needs to be tailored to the child's needs. 

Interventions are usually a range of specialist education and behavioural programmes. These work towards improving the skills of children with ASD. Some of the interventions include those that take hours of intensive work while others work in short therapy sessions. What works best depends on the severity of the child’s condition and the type of autism.

Aims of interventions

Interventions target improvement of:

  • Social interaction skills of the child so that he or she can understand other people's feelings and respond to them.
  • Communication and language development skills to develop ability to start and maintain conversations.
  • Cognitive skills to improve on imaginative play.
  • Academic skills that helps the child develop learning skills in reading, writing, drawing and maths.

Common interventions

Commonly used interventions for autism include:

Applied behavioural analysis (ABA)

This intervention works by breaking down skills like communication and cognitive skills into smaller and simpler tasks. The tasks are then taught in a highly structured way. The simple tasks over time coalesce into more complex skills that help in development.

Every task completed is rewarded and reinforced in a positive way and inappropriate behaviour as discouraged and redirected. This intervention can be applied at home and is applied by a consultant, who oversees the programme, and a team consisting of at least three therapists. They consist of 40 hours a week of intensive therapy over two to three years.

  • Early Intensive Behavioral Intervention (EIBI) 
  • This is a type of ABA for very young children with an ASD. The patients are usually younger than five, and often younger than three. 

This is another form of educational intervention that places great emphasis on structured learning by using visual prompts. Children with ASD often respond better to visual cues. This is delivered at special day centres and can be continued at home as well.

Early start Denver model

This is yet another behavioural intervention that combines applied behavioural analysis with developmental and relationship based approaches. The child is brought into interactive social relationships, using positive emotional exchanges and joint play activities. It improves cognitive, language and adaptive behavioural skills.

Discrete Trial Training (DTT)

This is a style of teaching that uses a series of trials and efforts to teach each step of a desired behavior or response.

Pivotal Response Training (PRT) 

This is intended to increase the child’s motivation to learn and monitor his or her own behaviour and begin communication.

Verbal Behavior Intervention (VBI)

VBI is a type of ABA that focuses on teaching verbal skills. 

Speech and language therapy (SLT)

This therapy aims at improving communication and language skills. This can improve their ability to interact with others socially. This intervention may use visual aids, stories and toys and other aids to develop language skills.

Occupational therapy

This focuses on development and maintenance of fine motor and adaptive skills.


There are no medications that can cure or reduce the symptoms of autism. Medications may however help in reduction of repetitive thoughts and behaviour and aggressive behaviour. For repetitive thoughts the class of antidepressants called selective serotonin reuptake inhibitors (SSRIs) are often prescribed. These work by altering levels of serotonin in brain. Serotonin is known to affect behaviour and mood. Children who have addition behavioural problems like Attention deficit hyperactivity disorder may benefit from drugs like Methylphenidate. Melatonin may be considered for treatment of sleep problems associated with ASD.

Alternative and complementary treatments

These include special diets, vitamin supplements, chelation therapy etc. There is little or no evidence that any of these approaches are effective, and some may even be potentially dangerous.

Autism History

The term autism first was used by psychiatrist Eugen Bleuler in 1908. He used it to describe a schizophrenic patient who had withdrawn into his own world. The Greek word ''autós'' meant self and the word “autism” was used by Bleuler to mean morbid self-admiration and withdrawal within self.

The pioneers in research into autism were Hans Asperger and Leo Kanner. They were working separately in the 1940’s. Asperger described very able children while Kanner described children who were severely affected. Their views remained useful for physicians for the next three decades.

Chronological history of autism

  • Eugen Bleuler coined the word "autism" in 1908 among severely withdrawn schizophrenic patients.
  • In 1943 American child psychiatrist Leo Kanner studied 11 children. The children had features of difficulties in social interactions, difficulty in adapting to changes in routines, good memory, sensitivity to stimuli (especially sound), resistance and allergies to food, good intellectual potential, echolalia or propensity to repeat words of the speaker and difficulties in spontaneous activity.
  • In 1944 Hans Asperger, working separately, studied a group of children. His children also resembled Kanner’s descriptions. The children he studied, however, did not have echolalia as a linguistic problem but spoke like grownups. He also mentioned that many of the children were clumsy and different from normal children in terms of fine motor skills.
  • Next Bruno Bettelheim studied the effect of three therapy sessions with children who he called autistic. He claimed that the problem in the children was due to coldness of their mothers. He separated the children from their parents. Kanner and Bettelheim both worked towards making hypothesis that showed autistic children had frigid mothers
  • Bernard Rimland was a psychologist and parent of a child with autism. He disagreed with Bettelheim. He did not agree that the cause of his son’s autism was due to either his or his wife’s parenting skills. In 1964, Bernard Rimland published, Infantile Autism: The Syndrome and its Implications for a Neural Theory of Behavior.
  • Autism came to be better known in the 1970’s. The Erica Foundation started education and therapy for psychotic children in the beginning of the 80s. Many parents still confused autism with mental retardation and psychosis.
  • It was in 1980’s that Asperger’s work was translated to English and published and came into knowledge.
  • It was in the 1980’s that research on autism gained momentum. It was increasingly believed that parenting had no role in causation of autism and there were neurological disturbances and other genetic ailments like tuberous sclerosis, metabolic disturbances like PKU or chromosomal abnormalities like fragile X syndrome.
  • Lorna Wing, along with Christopher Gillberg at BNK (Children's Neuro-Psychiatric Clinic) in Sweden in the 1980’s found the Wing’s triad of disturbed mutual contact, disturbed mutual communication and limited imagination. In the 1990’s they added another factor making it a square. The factor was limited planning ability.
  • Ole Ivar Lovaas studied and furthered behavioural analysis and treatment of children with autism. Lovaas achieved limited success at first with his experimental behaviour analysis. He developed it to target younger children (less than 5 years of age) and implemented treatment at home and increased the intensity (a measurement of the amount of “therapy time”) to about 40 hours weekly. Lovaas wrote Teaching Developmentally Disabled Children: The Me Book in 1981. In 2002, Lovaas wrote, Teaching Individuals With Developmental Delays: Basic Intervention Techniques.