by Mayer, Gwendolyn ¹, Perlea, Victor ¹

• ¹ Universitätsklinikum Heidelberg

This is the extended version, for the abridged version click here
The introduction and overview can be found here

Disclaimer:We have compiled this information to the best of our knowledge based on current scientific literature (as of May 2026). However, we do not provide diagnosis or treatment recommendations. If you notice any mental health concerns in yourself or in a child or adolescent in your care, please consult a medical doctor.

Diagnostic criteria

Autism spectrum disorders are characterised by impaired social interaction, communication difficulties and repetitive, stereotypical behaviours, as well as special interests. What formerly has been characterized by the categories “Childhood Autism”, “Asperger-Syndrome” and “Atypical Autism” has been replaced by ICD-11 and DSM-5 by a dimensional approach.
Autism spectrum disorders may display with and without impaired language and with and without intellectual disability.
However, the following criteria apply regardless of intellectual and language skills:
Essential (Required) Features of ASD according to ICD-11 (source: https://icd.who.int/browse/2025-01/mms/en#437815624, shortened):

• Persistent deficits in initiating and sustaining social communication and reciprocal social interactions, for example in:
  
  • understanding of and interest in the social communications of others
    
  • understanding of non-verbal cues, such as eye contact, gestures, facial expressions and body language
    
  • understanding and use of language in social contexts
    
  • ability to initiate and sustain reciprocal social conversations
    
  • ability to imagine and respond to the feelings and attitudes of others
    
  • mutual sharing of interests
    
  • ability to sustain peer relationships
  
  
• Persistent restricted, repetitive, and inflexible patterns of behaviour that are clearly atypical for the individual’s age and sociocultural context. These may include:
  
  • lack of adaptability to new experiences and circumstances
    
  • inflexible adherence to particular routines; e.g., geographic routines such as following familiar routes, or precise timing such as mealtimes
    
  • excessive adherence to rules (e.g., during game play)
    
  • excessive and persistent ritualized patterns of behaviour (e.g., preoccupation with lining up or sorting objects in a particular way) that serve no apparent external purpose
    
  • repetitive and stereotyped motor movements, such as whole body movements, gait, unusual hand or finger movements and posturing (particularly common during early childhood)
    
  • persistent preoccupation with one or more special interests, parts of objects, or specific types of stimuli or unusually strong attachment to particular objects
  
  
• Lifelong excessive and persistent hypersensitivity or hyposensitivity to sensory stimuli or unusual interest in a sensory stimulus, e.g., sounds, light, textures, odors, tastes, or pain.
  
• The disorder occurs during the developmental phase, typically in early childhood, but the characteristic symptoms may not fully manifest until later, when social demands exceed limited abilities.
  
• The symptoms result in significant impairment in personal, family, social, educational, occupational or other important areas of functioning.

Some individuals with autism spectrum disorder are able to function appropriately in many contexts through extraordinary effort, so that their deficits may not be apparent to others. A diagnosis of autism spectrum disorder is still appropriate in such cases.

Prevention measures

ASD cannot be prevented, but early intervention can help children and adolescents with ASD reach their full potential. Strategies include early and frequent developmental screenings and parental training. Routine developmental screenings should be conducted during paediatrician visits to detect early signs of the disorder. Parents should actively observe their child's development and discuss any concerns with their paediatrician. Special trainings, self-help groups and informational materials can be useful.

Risk factors

The question of the causes of ASD cannot be fully answered to date. Many different genes contribute to the disease and heritability has been estimated to range between 70 and 90 % (Genovese & Butler, 2023). It is further known, that prenatal environment plays a substantial role. Prenatal inflammation, endocrine disbalance, mitochondrial function and the gut microbiome can impair subsequent neurodevelopment (Love et al., 2024).

Treatment approaches / Intervention

It is important to understand that ASD cannot be cured, therefore. However, interventions can help people with ASD at all ages to develop skills, coping strategies and improve their quality of life. The most common approaches are:

• Psychotherapy: Psychotherapy won’t cure autism, but adolescents and adults with ASD often suffer from comorbid mental disorders such as anxiety or depression. Psychotherapy can contribute substantially to an improved self-acceptance and quality of life.
  
• ABA (applied behavioural analysis): this approach is based on the science of learning and behaviour and can have a positive impact on communication skills, cognitive performance and on the reduction of challenging behavioural patterns. Studies have shown that many sessions (25-40 per week) are needed to reach positive results in children. More: https://www.autismspeaks.org/applied-behavior-analysis Individuals with autism assess this method controversially, as harmful effects have been reported (see: https://www.autismtoday.com/applied-behavioral-analysis/ )
  
• TEACCH (Treatment and Education of Autistic and related Communication handicapped Children) is a training program developed by the University of North Carolina (see: https://teacch.com/trainings/). It includes creating structured and supportive physical surroundings, encouraging independence of students, setting routines, and providing visual support.
  
• Communication support by visual signs, e.g. PECS (Picture Exchange Communication System): PECS was developed in 1984 by L. Frost and A. Bondy in order to help people with ASD to initiate communication with the help of visual support: PECS
  
• Other helpful approaches can be chosen based on the individual needs of the person with ASD: Speech therapy, occupational therapy, and music therapy.

References for this article are here