Language note: Although individual preferences exist, surveys of the autistic community consistently show that autistic people prefer identity-first language rather than person-first language (i.e., “autistic person” rather than “person with autism”). This article reflects that community language preference.

The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision, defines autism as a neurodevelopmental disorder that occurs on a spectrum of severity. This language is misleading, as an individual may experience more symptoms in different environments or struggle in some areas but not others. Further, the levels of severity can also be misleading as support needs and traits may vary day to day and in different environments, all in the same person.

According to the DSM, an individual must meet the following criteria to be diagnosed with autism:

When a provider diagnoses someone with autism, they can specify severity by indicating whether the autistic person is Level One, Level Two, or Level Three; Level One indicates “mild” symptoms and Level Three indicates more severe difficulties.

If the diagnosing provider believes that the individual has “severe” autism, they are typically diagnosed with level three autism. According to the DSM, level three autism is characterized by the following:

Essentially, if the autistic person has high support needs and has difficulty functioning independently, they can be diagnosed with severe autism. Although some symptoms can be consistent across the lifespan, some autistic people experience an increase in symptom severity while they are experiencing burnout and require more support when this occurs.

Below are the main factors that indicate whether or not someone will be autistic.

Autism runs in families, and an individual is more likely to be autistic if they have an autistic parent or sibling.

Autistic people are at higher risk than the rest of the population for genetic disorders, possibly due to recessive genetic traits that have been linked to autism.

Comorbidity (which means being diagnosed with more than one condition) can affect the severity of symptoms. In other words, some autistic people who also have another type of genetic disorder (e.g.. Down's syndrome, cystic fibrosis, Turner syndrome, etc.) are at a higher risk for “severe” symptoms and high support needs compared to autistic people who have not been diagnosed with another disorder.

However, often symptoms that are attributed to “severe” autism are actually due to the comorbid genetic disorder. In these cases, individuals are labeled as having “severe” autism even though the term is not technically accurate.

Accurately labeling the source of various symptoms is an important part of researching these conditions, providing accurate information to the public, and reducing the stigma associated with an autism diagnosis.

Although no one factor causes an autistic person to exhibit “severe” symptoms, older parents are more likely to have autistic children than younger parents.

Older parents are more likely to produce children with recessive genes or mutations compared to younger parents, and some genetic presentations that correlate with autism are linked to these recessive traits.

Prenatal and postnatal factors can also correlate with more “severe” support needs in autistic individuals, including:

These early environmental factors may introduce stressors that contribute to autistic symptom presentation.

Because autism is a neurodivergent condition and not a mental illness, it is not something to be “cured” or “fixed.”

Consider what the goals are before seeking treatment for “severe” autism. Because autistic individuals who are labeled “severe” tend to have high support needs, they are at high risk for abuse or exploitation, and some in the autism industry promote interventions that are harmful or traumatic.

For instance, Applied Behavioral Analysis (ABA) Therapy is still widely used to "treat" autism, however, it forces autistic people to learn behaviors that are supposed to help them appear to be neurotypical or "normal." Many autistic people who have undergone this type of therapy report that it's a traumatic experience. In fact, a PTSD diagnosis is higher among autistic people who have undergone ABA than autistic people who have not.

Each person has unique needs, and no one treatment plan will be right for every situation. Depending on the person, they may benefit from:

Autistic people with high support needs may rely on caregivers for their health and safety. Caregivers should know that, even if the autistic person does not communicate through spoken language, they still have opinions and preferences, and they can communicate in other ways to express their needs. Focus on meeting their expressed needs in ways that they prefer and feel comfortable with rather than forcing one specific communication method.

Be mindful of the autistic person’s sensory needs and sensitivities. Try to maintain spaces that are sensory-friendly to the autistic person, and get their input in what their needs are for these spaces

Seek information about what services are appropriate and affirming by listening to the autistic community, and get feedback from other autistic people to ensure that you are centering and prioritizing the autistic person’s needs in their care. The Autistic Self-Advocacy Network is a good starting point for education, support, and resources for autistic people and their caregivers, and their resource database includes information that can help autistic people with various support needs.