Unit I: Introduction to ASD

1. ASD: Concept, definition and characteristics

2. Historical perspective – Cultural perspective, myths, and evolution of understanding the diagnosis till date

3. Prevalence and incidence

4. Types of ASD

5. Etiology, Recent Trends and Updates


1.     ASD: Concept, definition and characteristics

Definition, Types and Characteristics

Autism Spectrum Disorders (ASD) are complex neurological disorders that have a lifelong effect on the development of various abilities and skills. Helping students to achieve to their highest potential requires both an understanding of ASD and its characteristics, and the elements of successful program planning required to address them.

The term “spectrum” is used to recognize a range of disorders that include a continuum of developmental severity. The symptoms of ASD can range from mild to severe impairments in several areas of development. Many professionals in the medical, educational, and vocational fields are still discovering how ASD affects people and how to work effectively with individuals with ASD.

The Individuals with Disabilities Education Act (IDEA)

       A developmental disability affecting verbal and non-verbal communication and social interaction,(Age<3).

        Engagement in repetitive activities and stereotyped movements, resistance to environmental change or change in daily routines, and unusual responses to sensory experiences.

The Americans with Disabilities Act of 1990 (ADA)

       Autism is defined as a developmental disability significantly affecting verbal and non- verbal communication and social interaction, generally (< age 3), which adversely affects a child's educational performance


The most recent and updated version of the Diagnostic and Statistical Manual of Mental Disorders version 5 (DSM -5) of American Psychiatric Association has just a single category for the diagnosis of an autistic disorder – autism spectrum disorders, which include the following disorders that were previously discussed separately:

Autism or Autistic Disorder: Children who seem to have met most of the rigid criteria of a diagnosis of Autism are said to have Autism or Autistic Disorder. They have moderate to severe impairments in Social and Language skills, possess Repetitive Behaviors and Restricted Interests. Often the children and individuals with Autistic Disorder also have mental retardation and seizures.

Asperger’s Syndrome: Asperger Syndrome: AS, is the mildest form of Autism. It is found to have affected boys three times more in comparison with girls.

The most common symptoms of Asperger Syndrome are the children affected become excessively interested in a single subject or topic. They tend to find out and learn everything about their preferred subject and talk about it all the time. As compared with other form of Autism, children with Asperger have extremely good vocabulary however their social skills are markedly impaired and they are often awkward and uncoordinated.

It is also found that the children with Asperger’s Syndrome very often have normal or above normal IQ (Intelligence Quotient). As a result, many doctors address it as High-Functioning Autism. As children with AS enter into Childhood, they are at a high risk of developing Anxiety and Depression.

PDD-NOS (Pervasive Development Disorder, Not Otherwise Specified): PDD-NOS is a little complex syndrome to diagnose amongst children on the Autism Spectrum. Commonly children & individuals whose behavioral symptoms are more severe than Asperger’s Syndrome but less severe than Autistic Disorder are diagnosed as PDD-NOS.

No two children/individuals with PDD-NOS exhibit similar symptoms. This makes generalizing the disorder rather more complex. Commonly, children with PDD-NOS exhibit following symptoms:

Impaired social communication/interaction (similar to Autistic Disorder)

Better language/communication skills as compared to children with Autistic Disorder however these skills are not as good as of children with Asperger’s Syndrome

Lesser sensory dysfunction as a result fewer repetitive behaviors

Rett Syndrome : Rett Syndrome is severe form of Autism and it mostly occurs in girls. It is mostly caused by a genetic mutation wherein the mutation occurs randomly and has no inherited significance. It is a rare syndrome affecting about one in 10,000-15,000 girls.

In this syndrome, girls aging between 6 to 18 months of age regress marginally and lose linguistic and social skills. They habitually wring hands and develop coordination problems. Head growth slows down significantly and by the age of two their head appears to be far below normal. The treatment of Rett Syndrome focuses mostly on physical therapy and speech therapy to improve function.

Child Disintegrative Disorder : It is the least common and most severe form of Autism Spectrum Disorder. In CDD, the child rapidly loses multiple areas of function between the ages of 2 to 4 years of age. This regression takes place in social skills, linguistic skills as well as in intellectual abilities.

Very often the child develops a seizure disorder. The children with CDD – Childhood Disintegrative Disorder are severely impaired and don’t recover their lost function.

The number of children affecting CDD is lesser than 2 children per 100,000 children with Autism Spectrum Disorder. Boys are more commonly affected by CDD than girls.


Qualitative Impairment in Social Relationships: 

·      Children/individuals with Autism have limited or non-existent interest in, or desire to Socialise with others. Children with attention related disorders may have extremely poor skills but there is no lack of desire to relate to others.

·      Mothers may notice in the early weeks of life that their baby seems ‘different’ and shows little interest in them, may resist being cuddled or smiling. Infant interactive games such as ‘peek-a-boo’ and nursery rhymes are ignored.

·      The toddler may not watch other children and may not run up to play with them. Whilst the shy child may hide or refuse to join a group, the autistic child seems unaware of the group and doesn’t respond to it.

·      At times, autistic children are often termed as being socially “aloof”, will often ignore other people, and may seem unable to distinguish between people and objects.

·      Play is typically solitary, and often repetitive or restricted to a single type of object or activity.

·      The child cannot imitate, and may not wave or smile responsively.

·      Interactions initiated by the child serve only to achieve the child’s immediate wants and needs, rather than to make friends or play.

·      The older child may be unable to show empathy or understanding of other point-of-view or experiences, and will neither make nor desire friendships.

Extremely Rigid Pattern of Behaviour :

·      Almost every individual with Autism finds it extremely difficult to cope with the demands of a changing environment or set of expectations, or in generating rapid and appropriate responses to new experiences.

·      Once they have found a comforting or a pleasurable experience they will tend to repeat it endlessly. Thence their interests seem narrow and their behavior lacks flexibility or variation.


Non-Diagnostic Behaviours

·      An excellent photographic memory for places or things is often described in autistic children.

·      Unusual responses to sensory stimulation such as extreme responses to sounds – children may be fascinated with particular sounds and distressed by others.

·      Autistic children are frequently fascinated by bright or flashing lights and may spend hours watching rotating ceiling fan or other rotating objects. They may seem obsessed by spinning wheel of a toy car, mirrors and revolving parts of machinery.

·      Autistic children have described major difficulty in visual perception so that they have difficulty seeing objects as a whole. An adult autistic explained that “she had never seen a tree, just thousands of individual leaves.”

·      This type of visual perceptual difficulty can compound the difficulties experienced by autistic people in complex social situations and clearly interferes with much conceptual learning.

·      Hyperlexia is characterized by a preoccupation with print noted before the age of three years. In some cases hyperlexic children can read what they see, although usually without understanding.

·      Autistic children seem unduly sensitive to pressure on the skin – they may compulsively undress, taking tight garments off with obvious relief, or conversely they may seek and enjoy pressure on skin and joints.

·      They may show abnormal tactile response decrement – whilst most people do not feel their tight underwear or socks half a minute after they have put them on, the autistic person may continue to be aware of such sensations for hours. The children may spend hours in such tactile exercises as playing with a piece of silk, sandpaper, velvet or wood.


Language and Imagination

       Language has both verbal as well as non-verbal components. Both are impaired in Autistic Spectrum Disorder.

       Impaired non-verbal skills are manifest as poor or interpersonal synchrony, poor eye contact, an “empty gaze” or even a discomforting, piercing stare.

       Inappropriate body language such as unawareness of personal space – standing or sitting too close for conversational comfort.

       Absent or inappropriate gesture or smiling may include smiling which may seem unrelated to current experience.

       Individuals with Asperger Disorder may reach basic language milestones normally but their use of language is abnormal. They are unable to maintain a conversation, and understand the meaning of words only in their most literal sense, so that often unable to understand metaphor, sarcasm, puns or humor. Their speech is monotonous and like their facial expression, conveys little or no emotion.

       Expressive language is not simply delayed in autism, it seems to follow an abnormal or deviant developmental path. The child may repeat words or phrases just heard but not understood (Immediate Echolalia) or may suddenly repeat a sentence heard a day or two before (Delayed Echolalia).

       A severe deficit in Pragmatics can be identified Autistic people even if their expressive language is otherwise perfect or in many cases of Asperger Disorder.


2.     Historical perspective – Cultural perspective, myths, and evolution of understanding the diagnosis till date

       It has been established that before the discovery of the concept of what is now known as autism spectrum disorder, the people that did exist with the autism were considered under a single umbrella term and were called ‘mentally retarded’  or ‘insane’.

       Leo Kanner published his first paper identifying children suffering from autism in 1943, specifying that he had noticed such children since 1938.

        Kanner had observed that these children often demonstrated capabilities which proved that they could not be termed as slow learners, and despite that they didn't completely fit the patterns of emotionally disturbed children. Due to this he coined a new category, which he called ‘Early Infantile Autism’, which has since also synonymously been called Kanner's Syndrome.

       The following instance shows how people suffering from symptoms of autism were considered being ‘insane’.

        In the legal case of Hugh Blair, son of Scottish landowner who in 1747 appeared in the Edinburgh court for a decision to be taken with respect to his mental health and his ability to get married. His brother successfully petitioned for the marriage to get annulled to gain his brother’s inheritance.

       All that was known is that Hugh Blair had not suffered from any prior serious illnesses. The deficits in his social relationships included tactlessness and abnormal gaze; although in adult life he was affectionate and friendly. His obsessive and repetitive behaviour included odd motor mannerisms, collecting feathers and sticks, always sitting in the same seat in church and insistence that domestic items should be kept at the same place.

       At that time he was described as lacking common sense and suffering from ‘silent madness’.

       There have been many speculations about disabilities of those children who were known as ‘wolf children’, i.e. those children who were found in the wild and who were rumoured to be bred by wolves. Those children who were found tended to be mute and walked on all fours. Numerous cases were described at that time mostly in India and Ireland.

       The most celebrated of the ‘wolf children’ was Victor who was also known as ‘wild boy of ‘Aveyron’, found naked and covered with scars in the woods in 1798 aged about 11-12.

        Victor’s fame rests on the French physician Jean Itard’s attempts over a time period of 5 years to educate and ‘humanise’ him. At first Victor’s gaze was expressionless and was insensitive to noises and smells but still showed curiosity and sniffed at everything. He seemed melancholic and had frequent abrupt bursts of laughter and responded with joy to the sun, moon, and other elements of nature.

       Itard formed a systematic behavioural programme whose goals at first was to help him form social bonds, then to awaken his nervous sensibilities and then finally to guide him towards speech through imitation. As it was found Victor had a great memory and sense of order. Within 9 months he was able to match letters of the alphabet and in the course of next 5 years he learnt to distinguish emotions through different tones of voice and he became affectionate towards other people and loved helping other people.

       Over the course of many years there has been a change in the understanding and comprehension of Autism.

       In 1943, Leo Kanner's experimental study on 11 children led to the establishment of few particular traits related to autism.

        He discovered striking similarities of traits among these children, like difficulties in social interactions, difficulty in adapting to changes in routines, good memory, sensitivity to stimuli, resistance and allergies to food, good intellectual potential, echolalia or propensity to repeat words of the speaker and difficulties in spontaneous activity.

       Based on the outcomes, he proposed a term 'early infantile autism' to define children who have a 'powerful urge for aloneness' and 'an obsessive insistence on persistent sameness.‘

       Kanner's observation was based on a limited sample size which also led him to conclude that autistic children tend to have cold relations with their mothers. He coined a term, “refrigerator mothers” for this.

       Hans Asperger, a German scientist in 1944 had described a "milder" form of autism now known as Asperger's Syndrome. The cases he reported were all boys who were highly intelligent but had trouble with social interactions and specific obsessive interests.

       In 1967, Researcher 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 and referred to the term ‘refrigerator mothers’ first used by Kanner. He separated the children from their parents.

        Kanner and Bettelheim both worked towards making hypothesis that showed autistic children had frigid mothers.

       Later Bernard Rimland, who was a psychologist and parent of a child with autism, 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 1980 "Infantile autism" was listed in the Diagnostic and Statistical Manual of Mental Disorders (DSM) for the first time and also in addition to it, the condition was also officially separated from childhood schizophrenia.

        Then again in 1987 the DSM replaced "infantile autism" with a more expansive definition of "autism disorder," and included a checklist of diagnostic criteria.

       In 1980s, through the studies of Wing and Gould, more light was shed on the concept of autism and on the education of people suffering from autism.

       It was in 1980s that Asperger’s work was translated to English and published and came into knowledge.

        It was also in the 1980s that research on autism gained momentum. It was increasingly believed that parenting had no role in causation of autism which disproved Bruno Bettelheim’s research.

       In 1994, Asperger's Syndrome was added to the DSM, expanding the autism spectrum to include milder cases in which individuals tend to be more highly functioning.

       Recently in 2013, the DSM-5 folds all subcategories of the condition into one umbrella diagnosis of autism spectrum disorder (ASD). Asperger's Syndrome is no longer considered a separate condition. ASD is defined by two categories

       (1) Impaired social communication and/or interaction

       (2) Restricted and/or repetitive behaviours.

Screening and Diagnostic Assessments

Screening and diagnostic assessments for autism are usually made after detailed interviews with the family members, and after observations of and interactions with the individual with autism. The specific protocol used will depend on the age, skills and interests of the individual, as well as his or her background.

       Autism Diagnostic Observation Schedule (ADOS)

       The Autism Diagnostic Interview-Revised (ADI-R)

       CARS (Childhood Autism Rating Scale)

       GARS (Gilliam Autism Rating Scale)

       SCQ (Social Communication Questionnaire)

       SRS (Social Responsiveness Scale)

       MCHAT-R (Modified Checklist for Autism in Toddlers)

       ISAA (Indian Scale for Assessment of Autism)

3.     Prevalence and incidence

Prevalence is the number of people in a population that have a condition relative to all of the people in the population. Prevalence is typically shown as a percent (e.g. 1%) or a proportion (e.g. 1 in 100).

Autism spectrum disorder (ASD) is an important cause of developmental disability worldwide. Its estimated prevalence is 1% in the United Kingdom and 1.5% in the United States. There have been various epidemiological surveys to determine the prevalence estimates of ASD during the past decade. The data based on these surveys showed an increase in the prevalence of ASD worldwide. The prevalence was estimated to be 61.9/10,000 globally in 2012.

India is a populous country of nearly 1.3 billion people with children ≤15 years constituting nearly one-third of the population. It has been estimated that more than 2 million people might be affected with ASD in India. Most of the reported studies on ASD are based upon hospital-based data and thus lack information on the prevalence estimates of this disorder in India. There are only a few studies focusing on its prevalence in the community settings. Furthermore, lack of uniform application of fully validated and translated autism diagnostic tools makes it difficult to estimate the exact prevalence of ASD. There is also under-recognition of the disorder due to a delay in the diagnosis of ASD at a young age.

ASD not only affects the child and the family but also has direct and indirect cost implications on the nation as resources have to be utilized in providing health care, support for education, and rehabilitative services for these children. There is a lack of systematic reviews focused exclusively on the prevalence of ASD in India. Therefore, this study was designed to estimate the prevalence of ASD in Indian children below 18 years of age.

This systematic review reports a relatively low percentage prevalence of ASD in both rural and urban community-based settings in India. There were surprisingly lower number of prevalence studies present in the literature, and only four studies were found eligible to be included in this review. All the enrolled studies were recently published and specifically belonged to the time period between 2014–17. However, all the four studies, which were included in this systematic review, have used a varied spectrum of diagnostic tools for screening of autism. Some studies have used a single diagnostic tool and others have used more than one diagnostic tool to diagnose autism.

Autism is a developmental disorder with an early onset in childhood. There is no single screening tool that may be considered specific for the diagnosis of autism and which could be applicable worldwide. There are tools which are standardized to the local conditions and are being evaluated for their efficacy in establishing its diagnosis. Therefore, there might be an under- or over-estimation of the prevalence of ASD in different geographic distributions due to this variability in assessment. The ISAA is a locally developed standardized tool useful for the diagnosis of ASD. The ISAA includes screening questions pertaining to social relationship and reciprocity, emotional responsiveness, speech, language and communication, behavioral patterns, and has sensory and cognitive components.  However, it has been applied in only one study. The DSM-IV has been used for the clinical evaluation of screened children in two studies.

In a population-based prevalence estimate from the United States, the pooled estimated prevalence of ASD was 14.6 per 1000 (1 in 68) children aged 8 years. In a survey in the United Kingdom, the weighted prevalence of ASD in adults was 9.8/1000 (95% CI 3.0–16.5).
[1] In our systematic review, the pooled estimate of autism varied from the rural to the urban population from 14/10,000 to 12/10,000. These figures are relatively lower than those reported from the United States and United Kingdom. Our prevalence estimates were similar to the prevalence of 8.3/10,000 in children aged 3–12 years reported from the Chinese population.  A recent systematic review of the South Asian (Bangladesh, India, Sri Lanka) population has reported the percentage prevalence rate ranging from 0.09% to 1.07% among children in the age group of 0–17 years with ASD.

A study by Nair et al., (Centers for Disease Control and Prevention (CDC), Kerala 16) demonstrated the highest sample size with screening of 101,438 children. This study was conducted in Kerala and was aimed at diagnosing most of the developmental disabilities such as developmental delay, global developmental delay, autism, and cerebral palsy using simple and standardized screening tools. There is a need for such large population-based epidemiological surveys, which will be helpful in estimating the exact burden of ASD in our country. However, Nair et al., studied children in the age range of 0–6 years, which could be responsible for the observed low prevalence in this age group as the diagnostic yield is lower in the younger age group. Poovathinal et al., reported a relatively higher prevalence which could be due to the inclusion of children upto the age range of 15 years. However, the population screened by Nair et al., was larger, and therefore, the study had received a higher weightage in pooled prevalence estimates of the urban subgroup. It thus provided lower estimates in the urban setting.

Our systematic review had a few limitations. First, we could not perform quality assessment of the enrolled studies due to the lack of standardized and validated tools that specifically focus on the prevalence of ASD. Second, there was a heterogeneity in the methodology among the applied diagnostic tools used in the included studies, which might have led to under- or over-estimation of the prevalence data. Third, the enrolled studies were recent, and therefore, we could not perform a trend analysis of the prevalence rate. Fourth, our subgroup analysis on rural versus urban population might not have been robust because there was only one study that had included data on the prevalence of ASD in the rural setting.

Estimates of the prevalence of the disorder in the USA and other countries are controversial and have been moving towards an apparent increase in rates. Prevalence estimates range from 0.07% to 1.8%. Experts disagree about the causes and significance of the recent increases in prevalence of ASD. Despite hundreds of studies, it is still not known why autism incidence increased rapidly during the 1990s and is still increasing in the 2000s.

The importance of accurately identifying children with autism is of utmost importance, particularly given the apparently growing prevalence, considerable family and societal cost, and recognition of the importance of early diagnosis and intervention. In 1990, the Congress added autism as a separate category to federal law that guarantees special education services. Since then there has been an explosion of autism related treatments and services.

Though it is difficult to discuss the prevalence of autism without a universally acceptable definition, for this paper, unless otherwise indicated, Diagnostic and Statistical Manual of Psychiatric Disorders IV-TR (DSM-IV TR) (the American Psychiatric Association (APA), 2000) criteria which recognizes the category of Pervasive Developmental Disorders, under which the diagnoses of Autism, Asperger syndrome, and Pervasive Developmental Disorder Not Otherwise Specified (PPD-NOS) fall (along with Rett syndrome and Childhood Disintegrative Disorder), will be used. Later in the paper a comparison of the existing DSM-IV and newly instituted DSM-5 criteria will be discussed. With the next iteration of the DSM, the DSM-5, the category of Autism Spectrum Disorder (ASD) is officially recognized, having previously been used to capture autism, Asperger syndrome, and PDD-NOS and continuum of impairments represented by these diagnoses.

Recently (March 30, 2012), data from the Autism and Developmental Disability Monitoring Network Surveillance (ADDM), reported by the Centers of Disease Control and Prevention (CDC), indicated a significant increase in prevalence of ASD as follows.

(i)For 2008, the overall estimated prevalence of ASD among 14 ADDM sites was 11.3/1000 (1 in 88) children aged 8 years. Age varied by subtype of ASD (median earliest age ASDs were documented in their record: 4 years, 6 month).

(ii)This estimate varied widely across all sites, from 1 in 210 in Alabama to 1 in 7 in Utah (range: 4.8–21.2/1,000 children).

(iii)There were wide variations by gender and racial/ethnic groups.

(iv)Approximately 1 in 54 boys and 1 in 252 girls were identified as having ASD.


(i)white, non-Hispanic: 12.0/1,000,

(ii)black, non-Hispanic: 12.2/1,000,

(iii)Hispanic: 7.9/1,000,

(iv)Asian or Pacific Islander: 9.7/1,000.

The new numbers of ASD cases reported in 2012 by the CDC are the latest in a series of studies that have steadily raised the official autism estimates. These new figures mean that autism is nearly twice as common as estimated only five years ago. If these estimates for ASD (1 in 88 children) are valid and not an artifact of confounding or systematic bias due to better screening and ascertainment, then ASD affects more than 1 million children and adolescents in the United States.

A Comparison of these 2008 findings with earlier surveillance years indicates a dramatic increase in ASD prevalence over a short period:

(i)an estimated increase of 78% when the 2008 data was compared with data from 2002 (11.0/1,000 in 2008 versus 6.4/1,000 in 2002),

(ii)an estimated increase of 30% when data from 2008 was compared to 2004 (11.0/1,000 in 2008 versus 8.0/1000 in 2004),

(iii)there was an estimated increase in prevalence of 23% when the data from 2008 was compared with data from 2006 (11/1000 in 2008 versus 9/1000 in 2006).

Eight-Year-Old Children Diagnosed with Autism 2002–08













Because the ADDM Network sites do not make up a nationally representative sample, these combined prevalence estimates cannot be generalized to the USA as a whole.

Researchers have suggested that ASD onset, and prevalence are similar across European and North American populations. In Australia, a population based study indicated that the prevalence of ASD increased by 11.9% per annum among children born between 1983 and 1999 and diagnosed by age 8. With exception of Japan, the data are insufficient to measure ASD prevalence accurately in other cultures. For most studies conducted since 2000 in different geographical regions and by different investigators, estimates converge to a median of 17/10,000 for AD and 62/100,000 for all PDDs. For most regions median estimates are recorded except when there were too few estimates available within a given region. It should be noted that these values represent the best estimates currently available and represent median figures with substantial variability across the studies.


4.     Types of ASD

Autistic Disorder

This type of spectrum can also be known as “classic” autism. This type is usually what people think of when they hear the world “autism.” According to the Autism Support of West Shore, those with this type of spectrum disorder have “significant language delays, social and communication challenges, and unusual behaviors and interests.” These people are usually affected by intellectual disabilities as well. This type is considered the most severe form of autism and also the most common.

People who have autistic disorder may have problems with being touched by other people, perform restricted or repetitive behaviors, experience sensory overload, and may have issues communicating. Most other types of autism have the same symptoms, but this particular type means that those symptoms are much more severe.

Some people refer to ‘levels’ when speaking or writing about autism. To compare an autistic disorder to a level, you can most likely look at levels two and three on the spectrum, which are the most severe (three) and moderate (two). 

The experts at Autism Speaks discuss the three levels of autism in more detail and refer to the American Psychiatric Association’s Diagnostic and Statistical Manual for Mental Disorders (DSM-5 ). 

They consider level three as “requiring very substantial support,” level two as “requiring substantial support,” and level one as “requiring support.” As you can see, there is a continuum of severity and the level of support someone with autism will commonly need for each. 

Asperger’s Syndrome is the most mild form of autism and is closely associated with level one of ASD. 

Asperger’s Syndrome

This is one of the milder types of autism spectrum disorder. People with Asperger’s may experience the same symptoms as the other types, but they tend to be milder. Usually, people with Asperger syndrome have unusual behaviors and interests, in addition to social challenges. These symptoms tend to be the most difficult of this type of spectrum, as problems with language or intellectual disability do not tend to affect those with Asperger’s.

The autism experts at Applied Behavioral Analysis Programs list 10 common characteristics of someone who has Asperger’s Syndrome. 

Pervasive Developmental Disorder

This type of autism spectrum disorder is also known as “atypical autism.” This type is typically reserved for those who meet some of the criteria for the other two types, but not all of them. Those affected with PDD-NOS (Pervasive Developmental Disorder-Not Otherwise Specified) experience milder symptoms or fewer symptoms. Quite typically, those with PDD-NOS only suffer from social and communication challenges. These people tend to be the highest-functioning autistic types and simply do not fit into any of the other categories or types of autism spectrum disorders.

Many young children are diagnosed with pervasive developmental disorder after showing mild symptoms of autism in order to continue monitoring them. It may turn out after observation periods that the child is truly categorized within a level one or two; or it might turn out that the child actually does not even have autism at all. 

The autism experts at Applied Behavioural Analysis Programs state the following: 

“Usually a person is diagnosed with Pervasive Developmental Disorder if they exhibit social and communication challenges, but simply do not exhibit other symptoms of Asperger’s, like obsessions over certain topics, developmental delays, or awkward mannerisms. People with Pervasive Developmental Disorder typically live mostly ordinary lives and are considered the highest-functioning of all autism subtypes, but can have issues relating to people, understanding language, accepting change in surroundings or routines, and dealing with their own emotions.”


5.      Etiology, Recent Trends and Updates

Etiology of ASD

There are several theories about the cause or causes of ASD. Researchers are exploring various explanations but, to date, no definitive answers or specific causes have been linked scientifically to the onset of ASD. Research suggests that individuals with ASD experience biological or neurological differences in the brain.

In many families, there appears to be a pattern of ASD-related disabilities, which suggests that ASD is an inherited genetic disorder. Current research studies show that certain classes of genes may be involved or work in combination to cause ASD. There appear to be many different forms of genetic susceptibility but, to date, no single gene has been directly related to ASD (Autism Genome Project Consortium, 2007). Ongoing research is being done to further investigate the cause of ASD.

Latest Changes in ASD Definition (DSM-5)

The Fifth Edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) was released at the American Psychiatric Association’s Annual Meeting in May 2013; it marked the end of more than a decade’s journey in revising the criteria for the diagnosis and classification of mental disorders (http://www.dsm5.org). For the first time in nearly two decades, a panel of American Psychiatric Association researchers has rewritten the definition of autism. The group’s board of trustees voted on the proposals in December 2012 [34]. Field trials have been conducted for validation of the DSM-5 criteria for ASD. These trials were conducted to evaluate new diagnostic criteria that contain several important modifications relative to DSM-IV-TR diagnoses into a single broad ASD [35].

Among the Major Changes

(i)A new “autism spectrum” category was created describing symptoms that usually appear before age 3 and would encompass children with “autistic disorder” now referred to as severe cases, plus those with two high functioning variations.

(ii)Autistic disorder and high functioning variations: Asperger’s disorder and PDD-NOS would be eliminated, but their symptoms will be covered under a new category.

(iii)Another new category “social communication disorder” would include children who relate poorly to others and have trouble reading facial expressions and body language.

Although DSM-5 is now complete, a great deal of work, including the proper use of DSM-5, including providing training materials, questions about its implementation in clinical care, and research; clarifying concerns about the new ICD codes and insurance billing; and correcting any errors remains to be done.

There is concern among several groups of autism advocates and parents that the proposal will exclude as many as 40% of children now considered autistic. But the members of the panel that proposed changes maintain that none of the affected children will be left out and that the revision is needed to remove confusing labels and clarify that autism can involve a range of symptoms from mild to severe. The DSM-5 Neurodevelopmental Disorders Workgroup of The American Psychiatric Association has provided several documents and webinars to explain the changes and strengths of DSM-5, including the following statement in a symposium by Dr. W. D. Kaufman.

Criticisms of DSM-5 ASD Criteria

“Changes in criteria threaten services delivery.”

(i)Actually, a single diagnosis of ASD will improve access to services.

(ii)PDD-NOS and Asperger disorder do not qualify for services in 14 states.

(iii)Apparent biases in diagnostic labeling with rich, white males receiving (less-stigmatizing) dx of Asperger disorder, while poor, nonwhite males, and all females receive PDD-NOS (or autism).

It is somewhat ironic that these changes in the definition of autism are being proposed in the same year when CDC has reported a significant increase in autism cases (1 in 88 children as compared to previous estimate of 1 in 110) and advocacy groups have seized on the new increased rate as further evidence that autism research and services should get more attention.

Emerging Nutritional Risk Factors for Autism

In spite of decades of extensive research, the etiology of ASD is unknown. A number of risk factors being investigated include genetic, infectious, metabolic, nutritional, and environmental factors, with specific causes known in less than 10 to 12% of cases. In most cases, specific underlying causes cannot be identified. ASD is believed to have genetic and environmental origins, yet only in a small fraction of individuals specific causes can be identified. Though it is well established that ASD has a significant genetic component; for at least 70% of cases the underlying genetic cause is unknown. In this commentary a few nutrition related emerging risk factors which encompass both genetic and environmental aspects will be discussed.

Though ASD is considered an autoimmune disease it also appears to have several important diet and nutrient related risk factors. Although genetic contributions to autism etiology are well accepted, the rising prevalence and inconsistent finding from genetic studies suggest a role for interactions between susceptibility genes and environmental factors. A growing body of literature suggests that certain modifiable risk factors such as maternal metabolic syndrome and certain vitamins such as vitamin D and folic acid either in utero or early life, may be associated with increased risk of autism 

Though more than $1 billion has been spent during the past decade on ASD research, it is disappointing that the estimated prevalence of ASD has increased by 78% as compared to the 2002 estimates. Also, in the past two decades not much progress has been reported in untangling risk factors associated with ASD, or the factors which may be related to increased prevalence of ASD. However, recent identification of de novo gene mutation may account for a small but significant percentage of ASD cases. This research has opened up a large field for future discovery, diagnostics, and hopefully therapeutics. Furthermore, other modifiable, nutrition related risk factors such as folic acid, vitamin D, and maternal metabolic syndrome may account for some proportion of increase in ASD prevalence. Preponderance of evidence suggests a linkage between poor maternal folic acid status and/or folic acid levels during early childhood and autism related disorders. A better understanding of the metabolic basis of autism seems to have potential for the development of laboratory-based testing for autism diagnosis. Although findings so far do not conclusively implicate a dysfunctional folate-methionine pathway in the etiology of autism, the topic obviously deserves more effort and scrutiny studies have indicated that folic acid supplementation can normalize serum folate and folate-methionine metabolites. Whether this normalization affects behavioral measures is yet to be determined.

More research is also needed to further investigate quantitative genetic variations in various components of the vitamin D system. Poor maternal vitamin D status or early childhood vitamin deficiency or low activity of various vitamin D related enzymes may result in deficient activity in the vitamin D system crucial for brain development. Any of these conditions may result in ASD related disorders. Plausible mechanisms have been put forward to explain the palliative role of vitamin D in children with autism via DNA repair, anti-inflammatory actions, autoimmune activities, and increase in regulatory T cells or stimulation antioxidant pathways. Recruitment for an open label clinical trial to evaluate large doses of vitamin D in autistic children as a new treatment modality, with target 25-hydroxyvitamin D3 levels of 80 ng/mL is underway.

It is obvious that ASD research has a long way to go before developing precise yet inclusive diagnostic criteria, pinpointing relevant risk factors, and providing valid reasons for increasing prevalence of ASD.