Comprehensive Guide to Autism: Understanding the Spectrum

Lari Kharkongor
Sep 1
13 min read

What is Autism?

Autism spectrum disorder (ASD) is a complex neurodevelopment condition involving persistent challenges with social communication, restricted interests and repetitive behaviour. It is characterised by differences or difficulties in communication and social interaction, a preference for predictability and routine, sensory processing differences, focused interests, and repetitive behaviours.

According to the Centres for Disease Control and Prevention, an estimated one in 36 children has been identified with autism spectrum disorder. About 1 in 100 children has autism globally. The condition affects people across all demographics, though autism affects males four times more than females.

Key Characteristics of Autism:

Social Communication Differences: Challenges with back-and-forth communication, nonverbal communication, and developing relationships
Repetitive Behaviours and Restricted Interests: Repetitive movements, insistence on routines, highly focused interests
Sensory Processing Differences: Unusual reactions to sensory input like sounds, textures, or lights
Need for Predictability: Preference for routines and resistance to unexpected changes

Why is it Called "Autism Spectrum Disorder"?

The "Spectrum" Concept

The spectrum concept signals diversity rather than a simplistic range from mild to severe, and support needs can change over time and depend on context.

Why "Spectrum"?

Diverse Presentations: The term "spectrum" in ASD refers to the varying symptoms and severity. Each person's symptoms can vary.
Range of Abilities: Some are non-speaking or have developmental delays, while others speak fluently and show typical intelligence yet experience atypical social skills.
Variable Support Needs: While some with ASD can live independently, attend college and work professionally, others may need significant assistance with activities of daily living

Autism vs. Asperger Syndrome

Historical Context

Asperger Syndrome (AS) was first included as a diagnosis in DSM-IV in 1994, characterised by qualitative impairment in social interaction and restricted, repetitive behaviours without significant delay in language or cognitive development.

However, the DSM-5 now has only one broad category for autism: autism spectrum disorder (ASD), which replaces all previous disorders within the spectrum, including Asperger's disorder, pervasive developmental disorders (PDDs) and autism.

Reasons for the Change

The DSM-5 neurodevelopmental Disorders Workgroup aimed to acknowledge widespread consensus that Asperger syndrome is part of the autism spectrum, clean up a currently hard-to-implement diagnostic schema, and do away with distinctions made idiosyncratically across different centres.

Impact of Changes

Individuals with well-established DSM-IV diagnoses of Asperger's disorder should be given the diagnosis of autism spectrum disorder. No one should lose their diagnosis or services because of administrative DSM-5 changes.

Dimensional Approach

The DSM-5 takes a dimensional, as well as categorical, approach. Accompanying a diagnosis of autism spectrum disorder will be a comprehensive description of the individual's symptoms and strengths or impairments.

Benefits of Spectrum Approach:

Individualised Assessment: Recognises unique combination of characteristics in each person
Flexible Support: Allows for changing needs over time
Reduced Stigma: Moves away from hierarchical "high/low functioning" labels
Better Services: Ensures no individual currently diagnosed who needs support should lose that support

Modern Understanding

Today we understand the spectrum to mean each person with autism has a unique combination of characteristics. People with autism can be very different to each other, with different sets of strengths and challenges.

The spectrum acknowledges that autism manifests differently across:

Communication abilities (from non-speaking to highly verbal)
Intellectual functioning (from intellectual disability to neurotypical intelligence, and even savant like abilities)
Support needs (from minimal to 24-hour care)
Sensory processing (hyper- or hypo-sensitivity)
Social interaction patterns (from complete withdrawal to active but unusual approaches)

History of Autism

While one of the earliest recorded accounts of autism dates back to 1799, it centres on a boy in France who was initially believed to have been raised by wolves. The child, later named Victor, could not speak, appeared indifferent to heat and cold, and often spent hours rocking back and forth. Physician Jean-Marc-Gaspard Itard took responsibility for his education, focusing on developing Victor’s social, self-help, cognitive, and communication skills. More than 140 years later, these distinct characteristics were presented as what we now call autism.

The Founding Figures

Many psychologists and psychiatrists have contributed to the research and study of autism before it became known as we understand it today. Two of the most renowned pioneers in this field are Leo Kanner and Hans Asperger.

Leo Kanner (1894-1981) Leo Kanner was an Austrian-American psychiatrist best known for his 1943 landmark paper describing 11 children who displayed "a powerful desire for aloneness" and "an obsessive insistence on persistent sameness." He emphasised two essential features: autism (severe problems in social interaction) and resistance to change/insistence on sameness.

Hans Asperger (1906-1980) Hans Asperger, an Austrian-American psychiatrist described a group of children who shared many features with Kanner's patients but showed precocious interest in systems and how things work, despite social awkwardness. However, historical research has revealed that Asperger served Germany's National Socialist regime and participated in its child 'euthanasia' program.

Early Origins and Timeline

Year	Milestone	Key Figure	Contribution
1911	Term "autism" first introduced by Eugen Bleuler in his description of schizophrenia	Eugen Bleuler	Coined the term "autism"
1920s	Earliest research focused on children who would today be considered autistic	Grunya Sukhareva	First comprehensive definition of what is now considered autism
1938	Asperger used terms autistic psychopath and autism in a lecture	Hans Asperger	Early description of autism spectrum
1943	Kanner published "Autistic Disturbances of Affective Contact" describing 11 children	Leo Kanner	Established "early infantile autism" as distinct condition
1944	Asperger wrote article describing children sharing many same features as Kanner's patients	Hans Asperger	Described "autistic psychopathy"
1980	DSM-III defined autism as separate disorder from schizophrenia	APA	First official autism diagnosis
1981	Lorna Wing's influential paper "Asperger's Syndrome: A Clinical Account"	Lorna Wing	Introduced concept of autism spectrum
1994	DSM-IV introduced autism spectrum; included Asperger's disorder	APA	Expanded autism categories
2013	DSM-5 combined all autism diagnoses into single "autism spectrum disorder"	APA	Modern unified approach

Although there have been significant advances in understanding autism, history has not always been kind to individuals on the spectrum. In the past, there were distressing periods characterised by institutionalisation, forced sterilisation, and eugenics. Today, however, the focus has shifted towards improving the quality of life for those on the spectrum. From research initiatives to advocacy groups, the aim is to enhance understanding and foster a more compassionate and overall, a more accepting society.

Causes of Autism

Autism has multiple contributing factors, with research showing it results from complex interactions between genetic and environmental influences.

Genetic Factors

Several twin studies have suggested that aggregation within families is best explained by shared genes as opposed to shared environment. The variation of autistic traits in the general population has been shown to be highly heritable (heritability 40% to 80%).

Genetic Risk Factors:

Multiple genetic factors may increase autism risk in a complex manner. People with certain genetic conditions such as Fragile X Syndrome and Tuberous Sclerosis are at increased risk.
An estimated 200-1,000 genes impact autism susceptibility
The recurrence risk in siblings of children with autism is 2% to 8%, rising to 12% to 20% if including siblings with impairment in one or two domain.

Ultimately, it often comes down to chance in the genetic lottery.

Environmental Factors

According to recent evidence, up to 40–50% of the variance in autism spectrum disorder (ASD) liability may be influenced by environmental factors. It is important to stress that there is no single cause of autism, and it is certainly not the fault of any parent.

Decades of autism research reveal consistent trends: certain prenatal, perinatal, and parental factors are associated with a higher likelihood of autism. However, these links typically show modest effect sizes and should not be interpreted as direct causation.

The following table summarises the general patterns reported across large-scale studies and meta-analyses:

Risk Factor Category	Specific Factors	Evidence Level
Pregnancy-Related	Maternal infections, gestational diabetes, maternal obesity	Weak - moderate
Birth Complications	Severe birth complications associated with trauma, ischemia and hypoxia	Strong
Parental Age	Advanced parental age	Strong
Medications	Valproic acid and thalidomide when taken during pregnancy	Strong
Chemical Exposures	Bisphenol A (BPA), air pollution, endocrine disrupting chemicals	Emerging evidence

Characteristics and Traits

Core Diagnostic Features

According to DSM-5 criteria, to meet diagnostic criteria for ASD, a child must have persistent deficits in each of three areas of social communication and interaction:

A. Social Communication and Interaction Deficits:

Social-emotional reciprocity: Difficulty with back-and-forth conversation and social interaction
Nonverbal communication: Difficulty reading facial expression and emotional regulation
Developing relationships: Difficulty seeking interest in other people, preference for solitude

B. Restricted and Repetitive Behaviors (at least 2 of 4):

Repetitive motor movements or speech: Stereotyped speech, repetitive motor movements, echolalia
Insistence on routines: Rigid adherence to routines, extreme resistance to change
Restricted interests: Highly restricted interests with abnormal intensity or demonstrate monotropic thinking.
Sensory differences: Increased or decreased reactivity to sensory input

Associated comorbidity and autism

Comorbidities in individuals with autism include delayed language skills, delayed movement skills, delayed cognitive or learning skills, hyperactive/impulsive behaviour, epilepsy, unusual eating and sleeping habits, gastrointestinal issues, unusual mood reactions, anxiety disorder, and atypical fear responses.

Age-Related Manifestations

Age Range	Common Characteristics
Early Childhood (0-3 years)	Avoids eye contact, doesn't respond to name by 9 months, doesn't show facial expressions by 9 months
Toddlers (18-36 months)	Doesn't point to show interesting things by 18 months, doesn't notice when others are hurt by 24 months
School Age	Lines up toys and gets upset when order changed, repeats words or phrases over and over
Adolescence/Adulthood	Difficulties developing friendships, communicating with peers, understanding expected behaviours

Diagnosis

Diagnostic Criteria Evolution

The DSM-5 made significant changes to autism diagnostic criteria. Previously, five separate diagnoses were classified under "Pervasive Development Disorders." These have now been combined into one label: Autism Spectrum Disorder (ASD).

Assessment Process

Diagnostic Steps:

Developmental screening at regular pediatric visits
Comprehensive evaluation by specialists
Standardised assessment tools
Clinical observation and history

Key Assessment Tools

Tool	Full Name	Purpose	Age Range
ADOS-2	Autism Diagnostic Observation Schedule, Second Edition	Structured interactions and observations to evaluate social communication and repetitive behaviors	12 months to adulthood
ADI-R	Autism Diagnostic Interview-Revised	Structured interview with parents covering full developmental history	All ages
CARS-2	Childhood Autism Rating Scale	Rating scale assessing behavior across autism-related domains	Children
M-CHAT-R	Modified Checklist for Autism in Toddlers-Revised	Early screening	16-30 months
SRS	Social Responsiveness Scale	Questionnaire assessing social and communication skills	2.5-18 years

DSM-5 Severity Levels

The DSM-5 includes severity ratings based on support needs:

Level	Description	Characteristics
Level 1	"Requiring Support"	Difficulty initiating social interactions, unusual responses to social advances, decreased interest in social interactions
Level 2	"Requiring Substantial Support"	More pronounced social communication deficits, inflexibility that interferes with functioning
Level 3	"Requiring Very Substantial Support"	Severe deficits in social communication, extreme difficulty coping with change

Most children on the autism spectrum are diagnosed around the age of 2 or 3, as this developmental stage often reveals core characteristics, particularly in delay in language and social skills. There are claims, supported by both research and anecdotal reports, that autism can be detected as early as 18 months. In addition to a range of assessment tools, medical and biological tests are sometimes recommended to ascertain and address comorbidities such as seizures, gastrointestinal issues, or sleep problems. Diagnosing autism involves trained professionals and a multidisciplinary team, including doctors, psychologists, teachers, speech therapists, and parents.

Treatment and Interventions

Evidence-Based Treatments

The most effective treatments available today are applied behavioural analysis, occupational therapy, speech therapy, physical therapy. Treatment works to minimise the impact of the core characteristic and associated deficits of autism and to maximise functional independence and quality of life.

Current Treatment Categories

Treatment Category	Examples	Evidence Level	Target Areas
Behavioural Approaches	Applied Behavior Analysis (ABA), Early Start Denver Model (ESDM)	Moderate to Strong	Social communication, adaptive behaviors, learning skills
Educational Approaches	Evidence-Based Educational Practice, Social Skills Training	Moderate to Strong	Academic skills, social interaction
Communication Therapies	Speech-Language Therapy, AAC devices	Strong	Receptive/expressive language, social communication
Sensory/Motor Therapies	Occupational Therapy, Physical Therapy	Moderate	Sensory processing, fine/gross motor skills, daily living

Cognitive Behavioural Therapy claims to improve social wellbeing and anxiety management and the research shows its promising

Education

This topic really deserves its own post. If you’re interested in a deeper dive into how educational planning differs between the U.S. and the Netherlands, stay tuned—I’ll be writing a dedicated article. For now, I’ll give you a brief overview of what education typically looks like for a child with autism.

To qualify for special education services, a child must first be referred and then complete a comprehensive evaluation to determine eligibility. Once eligibility is confirmed, the family and the school team meet to develop an educational plan tailored to the child’s needs.

In the U.S., this plan is called an Individualised Education Program (IEP). The IEP is not only detailed and comprehensive, but also a legally binding document. It outlines specific learning goals for the child, along with the services (Speech and OT) and supports that will be provided. After the IEP is drafted, the team finalises it and sends it to the family. Parents are required to sign and give consent, but if they do not, the IEP automatically goes into effect after 14 school days. The lifetime of an IEP cannot extend beyond 365 days. During that time, families receive four progress reports to track their child’s progress. IEP meetings are held annually to review progress and adjust goals as needed.

In the Netherlands, a similar document exists, called the Student Support Plan (SSP) or an ontwikkelingsperspectief (opp) roughly translates to developmental perspective plan . The purpose of the SSP/OPP is much the same as an IEP—it outlines a child’s needs, goals, and communicates the required support. Depending on the school, the reviewing meetings may take place at the start and end of the school year, while in others, the team and parents meet every six months. Unlike the IEP, however, the SSP is not legally binding. The key difference lies in the legal framework: in the U.S., the IEP is protected under federal law through the Individuals with Disabilities Education Act (IDEA), whereas in the Netherlands there is no universal legal standard. Regardless, it is still an important tool used for educational planning.

The goals outlined in an IEP is dependent on the needs of the child. These goals cover academic (reading, writing, math), social skills, behaviour, self-help skills, communication (Speech), occupational therapy (OT) and Developmental Adapted Physical Education (DAPE). In the US, communication (Speech), OT and DAPE fall under related services and are provided for by special education staff but in the Netherlands speech and OT are provided by external professionals. While, a dedicated adapted PE isn't really a thing in international schools, Dutch special education schools have a variation of adapted PE.

Example of what goals might look like - Keep in mind: goals are uniquely tailored to the student's needs.

Communication: “Student will use functional words to request preferred items with 80% accuracy across 3 consecutive sessions.”
Social Skills: “Student will initiate appropriate greetings with peers during unstructured activities in 4 out of 5 opportunities.”
Academic: “Student will complete two-step math problems involving addition and subtraction with 90% accuracy.”
Behavioural: “Student will use pre-taught coping strategies during transitions with minimal prompting.”

Transitioning beyond school

Transition Planning

Transition planning for life after high school is essential. In the United States, this process typically begins when a student turns 16, though it is increasingly common to start as early as age 14. In the Netherlands, however, the Student Support Plan introduces the concept of uitstroombestemming—expected outcomes—much earlier. These outcomes are not fixed and may change as the child develops and progresses. Still, for many expat parents, seeing such expectations documented in the support plan can come across as an unpleasant surprise. Transition planning is designed to prepare students for adulthood, bridging the gap between school and life after graduation. This may include higher education, vocational training, independent living, and active participation in the community.

Conclusion

The understanding of autism has grown remarkably, shifting from efforts to “normalise” toward recognising strengths, addressing challenges, and supporting individuals across the lifespan. Progress is being made in the areas of treatments, better education, and stronger transition support, yet true acceptance remains a journey. Early intervention and school-age support are vital, and there is still important work ahead in ensuring young adults are supported with dignity and in building resilient systems that provide a safety net for those who may need a little extra help.

References and Citation

American Psychiatric Association. (2013). Diagnostic and Statistical Manual of Mental Disorders (5th ed.). Arlington, VA: American Psychiatric Publishing.
Centers for Disease Control and Prevention. (2024). Autism Spectrum Disorder (ASD). Retrieved from https://www.cdc.gov/autism/index.html
World Health Organization. (2023). Autism spectrum disorders. Retrieved from https://www.who.int/news-room/fact-sheets/detail/autism-spectrum-disorders
Kanner, L. (1943). Autistic disturbances of affective contact. Nervous Child, 2, 217-250.
Asperger, H. (1944). Die "Autistischen Psychopathen" im Kindesalter. Archiv für Psychiatrie und Nervenkrankheiten, 117, 76-136.
Wing, L. (1981). Asperger's syndrome: A clinical account. Psychological Medicine, 11(1), 115-129.
Lord, C., Rutter, M., DiLavore, P. C., Risi, S., Gotham, K., & Bishop, S. (2012). Autism Diagnostic Observation Schedule, Second Edition (ADOS-2) Manual (Part I): Modules 1-4. Torrance, CA: Western Psychological Services.
Chaste, P., & Leboyer, M. (2012). Autism risk factors: genes, environment, and gene-environment interactions. Dialogues in Clinical Neuroscience, 14(3), 281-292.
Love, C., Sominsky, L., O'Hely, M., et al. (2024). Prenatal environmental risk factors for autism spectrum disorder and their potential mechanisms. BMC Medicine, 22, 393.
Sandbank, M., Bottema-Beutel, K., Crowley, S., et al. (2020). Project AIM: Autism intervention meta-analysis for studies of young children. Psychological Bulletin, 146(1), 1-29.
Maenner, M. J., Warren, Z., Williams, A. R., et al. (2023). Prevalence and characteristics of autism spectrum disorder among children aged 8 years — Autism and Developmental Disabilities Monitoring Network, 11 sites, United States, 2020. MMWR Surveillance Summaries, 72(2), 1-14.
Happé, F., & Frith, U. (2020). Annual research review: Looking back to look forward – changes in the concept of autism and implications for future research. Journal of Child Psychology and Psychiatry, 61(3), 218-232.
Silberman, S. (2015). NeuroTribes: The legacy of autism and the future of neurodiversity. New York: Avery.
Baron-Cohen, S. (2017). Editorial perspective: Neurodiversity – a revolutionary concept for autism and psychiatry. Journal of Child Psychology and Psychiatry, 58(6), 744-747.
Lai, M. C., Lombardo, M. V., & Baron-Cohen, S. (2014). Autism. The Lancet, 383(9920), 896-910.
Centers for Disease Control and Prevention. (2024). Treatment and Intervention for Autism Spectrum Disorder. Retrieved from https://www.cdc.gov/autism/treatment/index.html
Children's Hospital of Philadelphia. (2017). Evidence-based Treatment Options for Autism. Retrieved from https://www.chop.edu/news/evidence-based-treatment-options-autism
DeFilippis, M., & Wagner, K. D. (2016). Treatment of Autism Spectrum Disorder in Children and Adolescents. Psychopharmacology Bulletin, 46(2), 18-41.
Hyman, S. L., Levy, S. E., Myers, S. M., et al. (2020). Identification, Evaluation, and Management of Children With Autism Spectrum Disorder. Pediatrics, 145(1), e20193447.
National Clearinghouse on Autism Evidence and Practice. (2020). Evidence-Based Practices for Children, Youth, and Young Adults with Autism. Frank Porter Graham Child Development Institute, University of North Carolina at Chapel Hill.
Autism Society of North Carolina. (2023). Evidence-based practices for autism treatment. Retrieved from https://www.autismsociety-nc.org/treatment/
Dawson, G., Rogers, S., Munson, J., et al. (2010). Randomized, controlled trial of an intervention for toddlers with autism: the Early Start Denver Model. Pediatrics, 125(1), e17-e23.
Wong, C., Odom, S. L., Hume, K. A., et al. (2015). Evidence-based practices for children, youth, and young adults with autism spectrum disorder: A comprehensive review. Journal of Autism and Developmental Disorders, 45(7), 1951-1966.
Steunpunt Passend Onderwijs. (2021, November 10). Het ontwikkelingsperspectief (OPP). Steunpunt Passend Onderwijs. https://www.steunpuntpassendonderwijs-povo.nl/document/het-ontwikkelingsperspectief/
Texas Education Agency. (2024). Autism: Special Education Services. Retrieved from https://tea.texas.gov/academics/special-student-populations/special-education/programs-and-services/autism
Rast, J. E., Roux, A. M., Anderson, K. A., & Shattuck, P. T. (2018). National Autism Indicators Report: Transition into Young Adulthood. Life Course Outcomes Research Program, A.J. Drexel Autism Institute.
Interagency Autism Coordinating Committee. (2024). Transition Resources for Autism. U.S. Department of Health and Human Services. Retrieved from https://iacc.hhs.gov/resources/transition/
Kaye, K. E., Allen, K. E., Smith, V. S., et al. (2024). Emerging Treatments and Therapies for Autism Spectrum Disorder: A Narrative Review. Cureus, 16(7), e63671.