What Is Severe Autism?

Also known as level 3 autism, it is the most severe form

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Severe autism is the most significant level of autism. Also known as level 3 autism, it often means a person is nonverbal or has very limited speech and restricted social communication skills.

Severe autism also often comes with sensory processing issues and extreme difficulty dealing with changes in routine. Common behavioral challenges include aggression, running or wandering away, and self-injury.

People with severe autism experience profound challenges and requires very substantial support. They are often unable to live independently and require 24-hour-a-day care.

This article discusses severe autism, its symptoms, and its challenges. It also explains the therapies available for people with severe autism and how to find caregiver support.

Other Names for Severe Autism

  • Classic autism
  • Kanner's autism (after the person who first described it)
  • Profound autism
  • Low-functioning autism (Note: This term is not used by most in the autism community.)

Severe Autism Symptoms

There are three levels of autism. Level 1 is considered more high functioning and independent, level 3 is the most debilitating form of the disorder, and level 2 is somewhere in between. Some symptoms of autism are common to all levels, while others are typically only present in people with severe autism.

To be diagnosed with autism, symptoms must impair daily life, and level 3 symptoms have the greatest impact in this regard. They lead to the most significant amount of disability and challenges, which is why round-the-clock support and supervision are usually needed.

Level 3 autism symptoms
 Verywell / Theresa Chiechi

Speech and Social Symptoms

Everyone with an autism spectrum disorder (ASD) has a difficult time with social skills and communication.

People with severe autism are most likely to be nonverbal, or entirely unable to use spoken language. They may also appear not to notice the people around them.

Sensory Dysfunction

Many people on the autism spectrum have sensory dysfunction. That means they're either too sensitive to or not sensitive enough to:

  • Light
  • Smell
  • Sound
  • Touch
  • Taste

Autistics also struggle with hidden sensory systems, including:

  • Interoception: Internal body cues like hunger, thirst, needing to use the toilet, and ambient temperature
  • Proprioception: The sense of self-movement, action, force, and location
  • Vestibular: Balance, spacial orientation, and coordination

People with severe autism tend to be extremely sensitive, to the degree that crowded, bright, or noisy environments can be overwhelming. Sensory overload can lead to an autistic meltdown.

Cognitive Challenges

Many people with autism have high IQs. But some have IQs at or near 75, the cutoff for what used to be called mental retardation.

Generally speaking, people with severe autism tend to have low to very low IQs, even when tested using non-verbal testing tools. It's important to know, however, that appearances can be deceiving.

Some people with severe autism can learn to communicate. They may use sign language, spelling boards, or other tools like augmentative and alternative communication (AAC) devices.

Some level 3 autistics are quite articulate. They prove that at least some people with severe autism are more capable than they may appear.

Repetitive Behaviors

Most people on the autism spectrum have repetitive behaviors and self-stimulatory behaviors.

Higher functioning individuals may flap their hands, rock, or flick their fingers. Often, they can control these behaviors for a period of time when necessary.

People with severe autism are likely to have many such behaviors. And those behaviors can be extreme and uncontrollable. Common ones are violently rocking, door slamming, and moaning.

Physical Symptoms

People with severe autism may have physical symptoms that only sometimes appear with less profound autism. These may include:

  • Sleeplessness
  • Epilepsy
  • Gastrointestinal issues

Because of their communication difficulties, such issues can go undetected or undiagnosed. Undiagnosed physical illness can lead to physical pain, which may cause of worsen behavioral issues.

Challenges in Level 3 Autism

The extreme behaviors associated with severe autism may stem from frustration, sensory overload, or physical pain.

Some people with severe autism express themselves through frightening behaviors. If the behaviors can't be managed, they can become dangerous.

In many cases, it's not safe for family members to live with a severely autistic teen or adult.


While self-injury can occur among people with milder forms of autism, behaviors such as head-banging and pica (eating non-food items) are far more common among people with severe autism.

Aggressive Behaviors

Aggression is relatively rare in autism. But it's certainly not unheard of, particularly among people with more severe symptoms (or those with other issues, such as severe anxiety).

People with level 3 autism may act out by hitting, biting, or kicking. They may also have behaviors, such as fecal smearing or door banging, that require a quick and effective response.


It's common for people with severe autism to wander off or run away. Often there's no obvious cause for and no intended destination. This is sometimes called eloping.

Making the situation worse, people with severe autism generally don't have the tools to communicate with first responders.

This can put the person with ASD in dangerous situations. In some cases, special locks, alarms, and identification tools are necessary to keep them from eloping.

Severe Autism Treatment

Severe autism isn't curable. However, many medical and non-medical treatment options can address symptoms. Some approaches are more common sense than anything else.

Using Medications

Treatments for severe autism usually include medications for anxiety and related issues. Anti-psychotic drugs and antidepressants can also be effective.

It's important to carefully monitor the autistic person's responses to drugs. Side effects or negative interactions can cause as many problems as they solve.

Incorporating Non-Medical Therapies

Children with severe autism often respond well to applied behavior analysis (ABA), a form of behavioral therapy often provided free by schools and early intervention programs.

Sensory integration therapy can be helpful for addressing serious sensory challenges. Other useful therapies include:

Checking for Physical Issues

Few people with severe autism are able to describe physical symptoms or problems. So, it's a good idea to regularly check for physical things that may be exacerbating problem behaviors.

It's not uncommon, for example, to discover that a child's apparently aggressive behavior is actually a response to severe gastrointestinal pain. That pain may go away with the right dietary changes.

Once the pain is gone, they usually find it much easier to relax, engage, learn, and behave appropriately.

Teaching Communication Skills

Even if someone with severe autism learns to use spoken language, they may have a hard time asking or answering questions. They may also repeat sounds without assigning meaning to them.

On the other hand, many of those same people who cannot speak are able to communicate through the use of sign language, picture cards, digital talking boards, and keyboards.

Communication, of course, is the key to any kind of engagement and learning.

Creating the Right Environment

Sensory issues can be minimized by creating a highly structured and low-stress environment. Things that may help someone with severe autism include:

  • A very regular routine
  • Low lights
  • Few loud noises
  • Predictable foods

Support for Caregivers

Parents and caregivers of people with severe autism often have a lot on their plate. Caregiver burnout is common.

It is important to learn to make time for yourself. Taking care of your emotional, physical, and social needs is crucial for caregivers.

Support services are often available and may include:

  • Caregiver support meetings (either for level 3 autism or all levels of autism)
  • Family care and case management to guide you through healthcare, education, and legal systems
  • Online support boards
  • One-on-one therapy or counseling
  • Parent coaching
  • Respite care to provide give you a much-needed break

In the United States, autism support services are often administered through the state or county health department. Search online for your state's department of autism services.


Severe autism, diagnosed as level 3, causes debilitating symptoms. Someone with level 3 autism may be non-verbal and be unable to engage with people. Sensory stimuli may be overwhelming. Cognitive deficits are common. Repetitive behaviors may be extreme and uncontrollable.

These symptoms make for significant challenges such as self-injury, aggressive behaviors, and eloping.

Treatment includes medications and additional therapies (physical therapy, speech therapy). With time and effort, the person with level 3 autism may be able to communicate.

A Word From Verywell

When someone in your life has severe autism, it can help to educate yourself about autism and how it's treated and managed. Work closely with the healthcare team and learn from them as well.

And as you navigate everything, remember that you are not alone in your experience (although it may feel that way sometimes). There are other people who understand exactly what you're going through.

Connecting with them may not only help you cope, but provide you with additional suggestions that can help ease your day-to-day life.

Frequently Asked Questions

  • How do you know if autism is severe?

    Level 3 autism has profound, noticeable symptoms. That said, only a clinician can formally determine if autism is severe.

  • Does autism get more severe with age?

    It's unlikely that new autism symptoms will arise with age, though they can worsen without intervention and/or as life circumstances change.

  • Does level 3 autism affect life expectancy?

    Yes. In one study, the mean age of death for someone with severe autism was 39.5 years. This compares to about 58 years for those with less severe autism and about 70 years for those without autism.

  • Can level 3 autism get better?

    Autism cannot be cured, and support for those with severe autism will always be needed. However, treatment can help a person better manage symptoms.

6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Lisa Jo Rudy
Lisa Jo Rudy, MDiv, is a writer, advocate, author, and consultant specializing in the field of autism.