Autism Spectrum Disorder: A Comprehensive Guide

Medically Reviewed By Dannell Roberts, PhD, BCBA-D

Autism spectrum disorder (ASD) is a neurological and developmental disorder. Autistic people may have social, communication, language, and behavioral differences. Their symptoms can range in severity, covering a broad spectrum of neurodivergence, or neurological differences. ASD is a condition that affects the development and function of the brain.

The term includes the word “spectrum” because different autistic people experience diverse ranges in symptoms. Some autistic people may need no help with daily activities and care, whereas others may need intensive, lifelong care.

The World Health Organization (WHO) estimates that 1 in 100 children Trusted Source World Health Organization Highly respected international organization Go to source may have ASD. However, this value might be higher due to barriers to diagnosis.

This article provides a detailed overview of ASD, including what it is and its symptoms, causes, and diagnosis. It also explains the outlook and answers some frequently asked questions about ASD.

Types of autism spectrum disorder

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In 2013, the Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-5) reclassified what were previously five separate conditions under one umbrella term of ASD.

In the past, clinicians may have referred to this group of disorders as “pervasive developmental disorders.”

These disorders were:

Today, someone who once could have received a diagnosis of one of the above conditions may instead receive a diagnosis of ASD.

However, although the DSM-5 says that all previous diagnoses now classify as ASD, many people still use the previous terms.

Read on for more information about the differences between Asperger’s syndrome and autism.

What are the symptoms of autism spectrum disorder?

Symptoms typically appear Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source in early childhood and continue for a person’s lifetime.

There is wide variation in what symptoms a person may experience. The main symptoms of ASD include social and language difficulties, unusually repetitive routines and behaviors, and developmental delays or disabilities.

Specific symptoms may include:

  • social avoidance, such as avoiding eye contact or having a lack of engagement or empathy with others
  • delays, regressions, or losses in skill in areas including:
    • socializing and communication
    • language
    • movement
    • cognition, or thought processing
    • learning
  • repetitive behaviors, such as:
    • repeating words
    • lining up or organizing objects
    • playing the same way every time
    • performing repetitive body movements, or stimming, such as hand flapping
  • obsessive interests
  • distinctive or inflexible eating or sleeping habits
  • anxiety, stress, or fear
  • a marked lack of fear
  • the need to follow a routine and discomfort with change
  • strong reactions to sensory inputs, such as the way things smell, taste, feel, sound, or look

Diagnostic levels of ASD

With the change in terminology and classification with the DSM-5, doctors may now also evaluate ASD by the following severity levels regarding social and behavioral symptoms:

  • level 1, meaning requiring support
  • level 2, meaning requiring substantial support
  • level 3, meaning requiring very substantial support

Serious symptoms that might indicate a life threatening situation

In some cases, autistic people can show behaviors that are violent or dangerous to themselves or others.

Seek immediate help or call 911 for anyone experiencing the following symptoms:

  • suicidal thoughts
  • a desire to hurt oneself or others
  • self-injurious behaviors
  • violent or threatening behaviors

What causes autism spectrum disorder?

Experts have not yet been able to confirm what causes ASD. Researchers are investigating numerous influences that may make people more likely to develop the condition, with evidence suggesting that certain genetic characteristics may be the most significant Trusted Source JAMA Peer reviewed journal Go to source factors.

These genetic factors may include having disruptions to brain growth during early development, having other family members with ASD, and having certain genetic mutations or chromosomal differences. Parenting practices do not cause ASD.

Vaccination and ASD

There has been a lot of discussion about whether or not childhood vaccines cause ASD.

Research supported by the Centers for Disease Control and Prevention (CDC) Trusted Source Centers for Disease Control and Prevention (CDC) Governmental authority Go to source and the World Health Organization (WHO) Trusted Source World Health Organization Highly respected international organization Go to source shows that vaccines do not cause ASD.

These organizations also emphasize that the benefits of vaccines outweigh any risks from them.

What are the risk factors for autism spectrum disorder?

Researchers have identified certain risk factors that can increase the likelihood of developing ASD. However, not all people who experience risk factors will develop ASD.

Risk factors for ASD include:

  • having certain genetic conditions, such as Down syndrome or fragile X syndrome
  • having a sibling with ASD
  • having biological parents who were older when they conceived
  • being assigned male at birth
  • experiencing infections or other health conditions during pregnancy, such as diabetes or folic acid deficiency
  • being born very prematurely or having a very low birth weight
  • experiencing complications before, during, or immediately after birth, such as fetal distress or breech presentation
  • having a birthing parent who was exposed to certain chemicals and pollution during pregnancy, such as:
    • valproic acid
    • thalidomide
    • serotonin reuptake inhibitors
    • misoprostol
    • pesticides
    • heavy metals

The National Institute of Environmental Health Sciences Trusted Source National Institute of Environmental Health Sciences Governmental authority Go to source clarifies that these factors are unlikely to cause ASD on their own. Instead, these factors may increase a person’s likelihood of developing ASD when they experience them in addition to certain genetic factors.

Researchers also clarify that more investigation is necessary to confirm risk factors.

How do you prevent autism spectrum disorder?

It is not possible to prevent ASD. However, early diagnosis and intervention can help make therapies more successful and aid the management of ASD. It can also improve the person’s quality of life.

Contact the child’s pediatrician about routine screening for ASD and early signs of ASD.

How do doctors diagnose autism spectrum disorder?

There is no one specific medical test to diagnose ASD. Instead, doctors may make use of developmental monitoring and screening to observe a young child’s development and presentation of ASD-associated symptoms over time.

The American Academy of Pediatrics Trusted Source Centers for Disease Control and Prevention (CDC) Governmental authority Go to source recommends regular developmental screening during ages 9–30 months.

Additional tests that may help diagnose ASD use an interview structure to evaluate the person’s social communication, interests, and interactive behaviors. These tests can include:

  • the Autism Diagnostic Observation Schedule, 2nd edition
  • the Autism Diagnostic Interview-Revised
  • the Social Responsiveness Scale for Adults

Learn more about the diagnosis of ASD.

Barriers to diagnosis

Although clinicians can diagnose ASD in childhood, many people do not receive an early diagnosis, and they may reach adulthood before exploring the idea of having ASD. This may be particularly true of people who experience lower levels of symptoms.

This can also happen due to Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source barriers to diagnosis and care. Examples of barriers to diagnosis include social stigma causing people to hide their symptoms and a lack of awareness and research about how different people present symptoms across marginalized groups. Also, some people may not have access to healthcare or social forms of support.

Additionally, clinicians sometimes tell Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source families to wait for evaluation and diagnostic testing in case the child achieves certain milestones later. However, this can delay effective treatment and support. Parents and caregivers of children or adolescents who may be autistic do not need to wait to advocate for help if they are experiencing symptoms.

ASD and medical vs. social approaches

ASD is diverse, and different people can have widely different experiences.

Not all autistic people will view their ASD as a condition that needs diagnosis or treatment. This may be particularly true for people with a lower level of symptoms and more independence, as others may need intensive support for daily life and care.

Barriers to diagnosis may also add to this point of view.

As a result, some people may want to focus on addressing social factors as an underlying cause or emphasize social or non-clinical forms of support.

What are the treatments for autism spectrum disorder?

There are a variety of treatment options that can improve quality of life for autistic people and reduce the effects of symptoms.

These approaches include methods that focus on behavior, development, education, and social interaction.

Treatment options can include:

  • Clinical therapies: Therapies such as behavior analysis and cognitive behavioral therapy can help address behavioral and psychological symptoms.
  • Occupational therapies: These include developmental approaches that focus on improving certain skills, such as speech therapy.
  • Medication: Medication will not treat the main symptoms of ASD, but it can address co-occurring symptoms to improve quality of life. For example, medication may help improve mental health, stomach problems, or seizures.
  • Educational approaches: Educational techniques aim to support learning by using techniques that may be more helpful to some autistic people.
  • Social support: This can refer to communication and relationship techniques. It can also refer to some non-clinical, or social, sources of support. Charities, advocacy groups, and peer groups may offer advice, programs, and other help for autistic people and any carers they may have.
  • Complementary or alternative treatments: These are treatments that can work alongside any relevant medical help or instead of it. Examples include animal therapy, mindfulness, and relaxation techniques. However, some complementary and alternative treatments have very little evidence supporting their effectiveness.

If you or a child you care for is experiencing symptoms of ASD, contact a doctor to discuss what treatment approaches may be most appropriate and effective.

Learn more about types of therapy for ASD.

What are the potential complications of autism spectrum disorder?

Having ASD may increase the risk of experiencing further conditions, such as:

Other frequently asked questions

Below are some other frequently asked questions about ASD.

Is autism the same as autism spectrum disorder?

People may use the word “autism” to refer to any diagnosis of ASD, and many people use the two terms — “autism” and “ASD” — interchangeably.

What are the 3 features of autism spectrum disorder?

The three core symptom areas of ASD are:

  • differences in or difficulties with social interaction and communication
  • repetitive behaviors
  • developmental delays

However, ASD is a diverse condition, and every autistic person will experience a different combination and level of symptoms.

How do you raise an autistic child?

One of the most significant ways you can support an autistic child is to make sure they receive the care that is right for them.

It is important to support a child through any social, behavioral, or mental health symptoms by looking for effective clinical and social support, even if they do not yet have a diagnosis of ASD.

Does autism go away?

There is no cure for ASD. However, researchers have observed that a very small number of people stop exhibiting symptoms of ASD with age. This seems to happen particularly with children who received intensive treatment at a young age and who initially displayed less severe symptoms.

It is important to note, however, that researchers are not yet sure why this happens or who it will affect. Additionally, one follow-up study suggests that these people still go on to experience other symptoms and conditions that impact their quality of life.

Can an autistic person live a ‘normal’ life?

The impact that ASD has on a person’s life will depend on the level of their symptoms and how much support they need and receive.

With appropriate support in place, many people with ASD can have an excellent quality of life and will be able to live independently. Others may need more extensive support and may never be able to live with complete independence.


ASD is a neurological and developmental disorder. It can cause differences in how people socialize, communicate, and behave, as well as some developmental delays or disabilities. Symptoms often appear in childhood, but some people reach adulthood before receiving a diagnosis.

ASD is very diverse in how it presents, and symptoms can vary widely in severity.

Researchers believe that the condition may be the result of certain genetic developmental factors.

Treatment options include different types of therapy, medications to address secondary symptoms, and social support. Early treatment is important in supporting an autistic person and improving their quality of life.

Contact a doctor if you believe that you or someone you care for is experiencing symptoms of ASD to discuss the best way to offer support for them.

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Medical Reviewer: Dannell Roberts, PhD, BCBA-D
Last Review Date: 2022 Jun 30
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