The autism spectrum encompasses a range of neurodevelopmental disorders characterized by challenges with social skills, repetitive behaviors, speech and nonverbal communication. There are 5 main disorders that fall on the autism spectrum:
Autistic Disorder (Autism)
Autistic disorder, sometimes called autism or classical autism, is the most common condition on the autism spectrum. According to the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), people with autistic disorder have persistent deficits in social communication and social interaction across multiple contexts. They also exhibit restricted, repetitive patterns of behavior, interests or activities. Symptoms are present in early childhood and limit or impair everyday functioning.
Some key signs and symptoms of autistic disorder include:
- Delayed language development and difficulty communicating
- Avoidance of eye contact
- Lack of interest in peer relationships
- Repetitive behaviors like rocking, hand-flapping or spinning
- Excessive interest in specific topics or objects
- Adherence to fixed routines and rituals
- Sensory issues like hypersensitivity to sound
Autistic disorder is considered the “classic” presentation of autism. It makes up the majority of autism spectrum disorder (ASD) cases.
Asperger’s Syndrome
Asperger’s syndrome is a developmental disorder characterized by challenges in social interaction and nonverbal communication, along with restricted interests and repetitive behavior patterns. However, people with Asperger’s syndrome do not experience language delays or intellectual disability.
Some key signs and symptoms of Asperger’s syndrome are:
- Difficulty with social interactions and nonverbal communication
- Clumsiness and uncoordinated motor movements
- Narrow, intense interests or preoccupations
- Repetitive routines or rituals
- Speech peculiarities like a monotone or fast rhythm
- Above average vocabulary but difficulty understanding figures of speech
- Sensitivity to specific textures, sounds or light
In the past, Asperger’s syndrome was considered a distinct condition. But the DSM-5 folded it into the broad diagnosis of autism spectrum disorder (ASD) in 2013.
Pervasive Developmental Disorder Not Otherwise Specified (PDD-NOS)
Pervasive developmental disorder not otherwise specified (PDD-NOS) is a diagnosis on the milder end of the autism spectrum. It’s given to individuals who meet some, but not all, criteria for autistic disorder or another ASD.
Key features of PDD-NOS may include:
- Impairments in social communication and interactions
- Challenges with transitions, organization and planning
- Repetitive behaviors or fixated interests
- Sensory processing differences
However, symptoms cause less impairment for those with PDD-NOS compared to classical autism. PDD-NOS was removed as a distinct diagnosis in the DSM-5, but many individuals previously diagnosed still identify with the label.
Childhood Disintegrative Disorder
Childhood disintegrative disorder (CDD) is a rare condition characterized by significant regression in language, social skills and motor function after several years of typical development. According to the DSM-5, onset occurs between ages 2 and 10.
Key signs and symptoms include:
- Marked decline in communication, social interaction, play and motor skills
- Impaired functioning across multiple areas
- Loss of interest in surroundings
- Loss of previously acquired skills in at least two areas (e.g. language, social abilities, bowel control)
CDD has similarities to autistic disorder but involves distinct regression after normal development. Some experts posit it may represent an extreme variant of ASD. Prevalence is estimated around 1-2 cases per 100,000 children.
Rett Syndrome
Rett syndrome primarily affects females and causes impaired growth, communication problems, repetitive hand movements and difficulty walking. According to the DSM-5, symptoms emerge between 6-18 months of age following a period of apparently normal development.
Distinctive features of Rett syndrome include:
- Decelerated head growth
- Loss of previously acquired purposeful hand skills
- Development of hand movements like wringing, clapping or rubbing
- Severely impaired expressive and receptive language
- Apraxia, ataxia or tremors
Rett syndrome is associated with mutations in the MECP2 gene. It almost exclusively occurs in females, though some males have a severe fatal encephalopathy. Prevalence is estimated at 1 in 10,000-15,000 females.
Conclusion
In summary, the 5 main disorders classified on the autism spectrum are:
- Autistic disorder (classic autism)
- Asperger’s syndrome
- Pervasive developmental disorder not otherwise specified (PDD-NOS)
- Childhood disintegrative disorder (CDD)
- Rett syndrome
Though symptoms vary, these disorders are all characterized by challenges with communication, social skills, restricted interests and repetitive behaviors. Increased awareness and understanding of the range of autism spectrum disorders can help improve diagnosis and access to support.