What Is Atypical Autism?

Reviewed by:
Hannah Andreasen

April 23, 2022

Atypical autism, also known as PDD-NOS (Pervasive Developmental Disorder-Not Otherwise Specified), is defined by the ICD-10 as a pervasive developmental disorder that does not meet the diagnostic criteria for autism. The term "atypical autism" was first used in the fourth edition of the Diagnostic and Statistical Manual of Mental Illnesses (DSM-5), a textbook reference used by medical practitioners to identify and diagnose mental disorders.

Due to unusual symptoms, late-onset age, or both, the phrase was used to designate anybody who didn't fall into the Pervasive Developmental Disorders categories: 

  • Autistic disorder or severe autism
  • Asperger syndrome
  • Childhood disintegrative disorder
  • Rett's syndrome

Atypical autism is considered a moderate form of autism that does not always necessitate treatment or therapeutic involvement.

Atypical autism overview

According to ICD-10, the symptoms and deficits of atypical autism appear after the age of three or do not appear in the three areas of autism: 

  • Social interaction
  • Communication
  • Restricted, repetitive, or stereotyped behavior.

Atypical autism affects those with significant intellectual disabilities whose low level of functioning prevents them from engaging in some activities, as well as those with severe receptive language difficulties.

The characteristics of atypical autism remain a topic of debate. While some experts feel that atypical autism is just a milder version of classic autism, others argue that its clinical characteristics and links to other conditions distinguish it as its own condition.

Overall, research suggests that the average severity of atypical autism cases is somewhere between classic autism and Asperger syndrome, which is linked to better social and cognitive functioning.

Subgroups of atypical autism

A publication by Darlene Walker in 2004 examined the degree of functioning of children with autistic disorder, Asperger syndrome, and atypical autism in research published in the Journal of the American Academy of Child & Adolescent Psychiatry.

In addition to discovering that atypical autism is often a mild form of classic autism, this team discovered three separate subgroups that satisfied the diagnostic criteria for classic autism.

1. With limited stereotypy

Children who match all the diagnostic criteria for autistic conditions but lack repetitive behaviors make up a majority of atypical autism, accounting for more than half of all cases. As a result, social deficits are far more common than stereotypy and interest restrictions.

2. Incomplete autism criteria

According to the findings, 25% of individuals with atypical autism have symptoms in the three areas crucial to the diagnosis (communication, interaction, and stereotyped behaviors). However, the symptoms aren't severe enough to match the diagnostic criteria..

3. High functioning

The third class of atypical autism resembles Asperger syndrome and is characterized by generally normal language performance.  This subtype also accounts for around a quarter of the population.

The symptoms of atypical autism

Atypical autism also has traits that are comparable to those linked with a regular diagnosis of an autistic disorder, although they are milder. They are as follows:

  • Inappropriate social conduct
  • Unusual development of motor, cognitive, and visual or spatial perception skills
  • Slow speech and language development and comprehension, and communication loss, both nonverbal and verbal
  • Change in taste, sight, hearing, smell, and touch sensitivity

Even though atypical autism emerges with fewer symptoms, individuals with this type of autism face significant challenges. In a study conducted by the American Academy of Child and Adolescent Psychiatry, children with atypical autism were compared to those with autistic disorder and Asperger syndrome.  The study found half of the children with atypical autism displayed some repetitive behaviors that were characteristic of autism, but did not match the disability's criteria. A quarter of the kids exhibited just minor linguistic or cognitive developmental problems. The remaining quarter had a late onset of autism or were too young to meet the criteria for an autism diagnosis.

Even if the atypical autism diagnosis confirms mild symptoms, health professionals would advise using standard treatments that are effective for children across the autism spectrum including ABA, speech, occupational, and physical therapy, behavior and developmental therapy, and social skills classes for older children.

Atypical autism diagnosis

Atypical autism manifests itself in children who have a wide range of talents, making diagnosis difficult. Furthermore, because its symptoms are generally milder and less disruptive than those of autistic disorder, atypical autism may be difficult to diagnose.

However, atypical autism is no longer an accepted diagnosis and will not be diagnosed by a child's doctor because it is not included in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5). A child may be diagnosed as being on the autism spectrum and given a severity level based on the amount and intensity of diagnosable traits.

Treatment or therapies for atypical autism

Early detection and intervention will aid in overcoming a variety of problems, including primary functioning, independence, and adulthood. Therapy can begin at any stage of autism. Here's a rundown of some of the most frequent therapies and services:

  • Occupational therapy
  • Physical therapy
  • Speech therapy
  • Applied Behavior Analysis (ABA)
  • Social skills classes

Atypical autism manifests itself differently in each person with a unique set of obstacles and issues. As a result, atypical autism therapies must be personalized based on an accurate diagnosis by a medical professional and a review by a  Board Certified Behavior Analyst (BCBA).  Symptoms, the individual's behavior history, communication abilities, social functioning, and cognitive skills should all be included in the evaluation. 

Note: For a young kid with atypical autism, parents should seek an Early Intervention Program (EIP) and an Individualized Education Program (IEP) for children over 5 years of age.

Final thoughts

Atypical autism has a reputation for being a "less difficult" kind of autism to live with. However, even though certain symptoms are milder than those in classic autism spectrum conditions, the symptoms that are present can still alter your child’s quality of life, even into adulthood.

Atypical autism needs the same amount of intervention, care, and continuous therapy as other levels of autism. The treatment's intensity will be determined by the unique circumstances of each child.

For personalized therapies and a devoted team of therapists to take care of your child, get in touch with Songbird. Songbird Therapy is a technology-enabled provider setting a higher standard for children’s autism care. With a deeply passionate team and innovative technology, we’re building a world where every child can access world-class care at home, uniquely tailored to them. technology-enabled provider setting a higher standard for children’s autism care.