• Clinical science

Autism spectrum disorder


Autism spectrum disorder (ASD), also known as pervasive developmental disorder, is a neurodevelopmental condition characterized by core features seen in all affected individuals. These features include qualitative impairment in social interaction and communication, as well as repetitive stereotyped behavior, interests, and activities. ASD may be further classified into Kanner's syndrome and Asperger's syndrome. Whereas children with Kanner's syndrome show marked impairment in language abilities and reduced intelligence, children with Asperger's syndrome show appropriate language development and pronounced skills in specific areas. Diagnosis is based on careful assessment of behavior, cognitive development, and language skills. Treatment should be initiated early, and involves educational and behavioral management, medical therapy, and family counseling.


  • Global prevalence: 7.6/1000
  • Sex: > (4:1)
  • Age: symptoms typically evident before 2–3 years of age
  • Associated with a higher head:brain ratio [1]


Epidemiological data refers to the US, unless otherwise specified.


  • Complex, multifactorial
    • Genetics: strong underlying predisposition; ; many genes have been associated with autism spectrum disorders
    • Environmental factors (e.g., toxin exposure, prenatal infections) may increase the risk; however, no specific causes have been identified.


Overview of ASD

General clinical features

  • Core features
    • Persistent impairment in communication and social interaction
    • Restricted, stereotyped patterns of behavior, interests, and activities
  • Additional features
    • Intellectual impairment
    • Language impairment
  • Associated conditions

Overview of DSM-IV subtypes

All pervasive developmental disorders present with a varying degree of qualitative impairment in social interactions and communication, and restricted, stereotyped patterns of interest and activities. In addition to the core symptoms of ASD, each subtype has unique distinguishing features.

Autistic disorder/childhood autism

(Kanner syndrome)

Pervasive developmental disorder, not otherwise specified Asperger syndrome Rett's syndrome

Childhood disintegrative disorder (Heller dementia)

Distinguishing features
  • Impaired language competence, reduced intelligence
  • Impaired communication with parents (e.g., no eye contact)
  • Reduced emotional response in social situations (e.g., no reciprocal smiling)
  • Repetitive movements (e.g., stereotyped hand movements)
  • Fixation and intense attachment to certain objects
  • Easily disturbed by small changes in surroundings, react with fear and panic
  • Symptoms do not fulfill the criteria of a specific pervasive developmental disorder
  • Normal language and cognitive development (normal or high IQ)
  • Exceptional skills/interests in specific areas
  • Reduced ability or inability to empathize
  • Impaired emotional expression and emotional intelligence
  • Stereotyped repetitive behavior patterns
  • Increased risk of ADHD, obsessive compulsive disorder, anxiety disorders, schizophrenia
  • Normal development and then onset between 7–24 months of age
  • Loss of motor, cognitive, and language competences
  • Stereotypical hand movements (hand-wringing)
  • Initially normal development, then subsequent loss of acquired skills within several months

ICD-10 classification



  • Comprehensive evaluation of
    • Social interaction and communication skills
    • Language and comprehension competence
    • Behavior
    • Cognitive development
    • Associated conditions
  • Hearing and vision testing: rule out comorbidities or other causes of developmental delays and behavioral disorders.
  • Genetic testing: fragile X syndrome, tuberous sclerosis



  • Early behavioral and educational management
    • Competence training: social skills, communication skills
    • Establishing clear and consistent structures
  • Family support and counseling: e.g., parental education on interaction with the child and acceptance of his/her behavior.
  • Medical treatment .



  • Indicators of poor prognosis: : severe core symptoms, cognitive impairment (low IQ), poor or absent language skills, late initiation of treatment
  • Impaired social interaction often persists into adulthood.
  • The majority of patients depend on their family and familiar surroundings.
  • Individuals with good language and cognitive ability usually learn to cope with their particularities.
  • Approx. 50% of individuals with language impairment do not develop phonetic speech ability.
  • Adolescents: Insensitive behavior towards their peers often results in social exclusion.