Pervasive Developmental Disorder (PDD)

Reviewed by:
Hannah Andreasen

January 5, 2023

Pervasive developmental disorder (PDD), also known as atypical autism or subthreshold autism, refers to a subtype of autism spectrum disorder (ASD) characterized by developmental delays in socialization and communication skills.

What Is PDD?

PDD was one of several diagnoses that were rolled into the single diagnosis of autism spectrum disorder (ASD) when the newest version of the Diagnostic and Statistical Manual of Mental Disorders (DSM) was released in 2013. The DSM is used by many professionals around the world to diagnose psychiatric disorders. 

The previous edition of the DSM included five subcategories of PDD:

  • Autistic disorder
  • Asperger’s disorder
  • Rett’s disorder
  • Childhood disintegrative disorder (CDD) 
  • Pervasive developmental disorder not otherwise specified (PDD-NOS)

In the new version of the DSM, Autistic disorder, Asperger’s disorder, and PDD-NOS have been replaced by a single diagnosis of ASD. Those diagnosed with autism after 2013 most likely will not carry a diagnosis of PDD. However, if you were diagnosed before 2013 you may recognize this term. 

In the past, someone might be diagnosed with PDD if they met some, but not all, of the criteria for autism. A person might not meet all the criteria for an autism diagnosis if they are diagnosed at an older age or have mild or atypical autism symptoms. 

The DSM changes reflect research showing autism symptoms as falling along a continuum, with mild symptoms at one end and severe symptoms at the other end of the spectrum. Individuals who have received a diagnosis of PDD in the past might be diagnosed with ASD along with a severity rating.

What Are the Symptoms of PDD?

The symptoms of PDD are very similar to that of ASD. Children with PDD can have a wide range of behaviors and abilities. 

PDD is characterized by developmental delays in social communication; repetitive and restrictive special interests, routines, or activities; and impairments in speech and language. 

Some of the symptoms include:

  • Avoiding eye contact
  • Delays in learning and understanding language 
  • Difficulty relating to others
  • Differences in how the child plays with toys or other objects (such as lining up or organizing toys or playing with them the same way every time)
  • Difficulty with changing a routine 
  • Repetitive body movements (like hand flapping, rocking, or spinning)
  • Restricted interests 
  • Unusual response to light, sound, taste, smell, or touch 
  • Preference for being alone
  • Repetition of words or phrases 

What Are the Subgroups of PDD-NOS?

Studies suggest that there are three subgroups of PDD-NOS. 

The first group is a high-functioning group. This group generally has mild symptoms but does have some delay in language and mild cognitive impairment.

Those in the second group have similar symptoms to autistic disorder but do not fully meet all the diagnostic requirements.

Those in the third group meet the diagnostic criteria for autistic disorder but have mild stereotypical and repetitive behaviors.

How Is PDD Diagnosed?

Diagnosis requires monitoring a child’s achievement of developmental milestones. A pediatrician or pediatric psychiatrist will make the diagnosis. 

In the past, a child may be given a diagnosis of PDD if they had some signs and symptoms of autism, but did not meet the full diagnostic criteria. Today, a child is given a diagnosis of ASD along with a severity rating. 

A person is classified as having level 1, level 2, or level 3 autism based on their condition and how much support they need in their everyday lives. 

Those with level 1 autism require some support. 

Those with level 2 autism require more substantial support. 

Those with level 3 autism require very substantial support.

How Is PDD Treated? 

There is no cure for autism, but many treatment options can help improve symptoms. Outcomes are usually improved with early intervention.

Studies have shown that when compared to children with other ASD diagnoses, children diagnosed with PDD who receive treatment at an early age are more likely to no longer exhibit ASD symptoms later in their development. 

There are many treatment approaches available for PDD. Treatment should be tailored to meet the individual needs of each child. 

Behavioral Approach

Behavioral approaches focus on changing behavior based on an understanding of what happens before and after the behavior. Behavioral treatment methods commonly use the science of applied behavior analysis (ABA). ABA therapy is supported by years of research supporting the effectiveness of these methods in the treatment of autism symptoms. 

ABA methods can help to increase desired behaviors and decrease harmful ones. This method uses positive reinforcement and knowledge of how behavior works to teach new skills and behaviors. 

The Early Start Denver Model is an example of a proven early behavioral intervention using ABA methods.

Developmental Approach

Developmental approaches are commonly combined with behavioral approaches. Developmental approaches include speech-language therapy, occupational therapy, sensory integration therapy, and physical therapy. 

Educational Approach

This approach is provided in a classroom. The most common method is the TEACCH method. This method uses structure, visual cues, and routine to help improve learning and build a child’s independence. 

Social-Relational Approach

The social-relational approach focuses on improving social skills and building emotional relationships. Examples of this method include Floortime and social stories. 


Although the term PDD is no longer used, people who were diagnosed before 2013 may still carry this diagnosis. Today, PDD is included in the diagnosis of ASD. The symptoms of PDD are the same as ASD, but may not be as severe. Early diagnosis and treatment of PDD is important for improving outcomes later in life. 

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.