Autism spectrum in ICD-11: diagnosis and profile

From separate ICD-10 categories to one spectrum

In ICD-10, autism belonged to the group of pervasive developmental disorders. This group included separate categories such as childhood autism, atypical autism, Rett syndrome, other childhood disintegrative disorder, Asperger syndrome, and other and unspecified pervasive developmental disorders. That model suggested several relatively distinct types, although in practice the boundaries between them were often unclear.^[3]

ICD-11 takes a different approach: most former categories are included within one diagnosis, autism spectrum disorder (6A02). The classification no longer asks primarily: "what type of autism?", but: "are the diagnostic requirements for ASD met, does disorder of intellectual development co-occur, and what is the level of functional language?".^[4]

This change better reflects the heterogeneity of the spectrum. Autistic people can differ greatly in independence, communication, support needs, cognitive functioning and adaptive functioning. ICD-11 tries to describe that diversity through the current functioning profile rather than through historical type labels.

Comparison table: ICD-10 vs ICD-11

What happened to Asperger syndrome?

Asperger syndrome may still function as a historical, identity-based or everyday term, but in ICD-11 it is not an independent diagnostic category. A person who previously received an Asperger syndrome diagnosis would most often now be described as having ASD without disorder of intellectual development and with mild or no disorder of functional language (6A02.0). This does not mean, however, that every former diagnosis should automatically be converted to 6A02.0.

The separate category was removed because of diagnostic problems. The boundary between former Asperger syndrome and so-called high-functioning autism was often unclear. A similar clinical picture could lead to different diagnoses depending on speech development history, the clinician's interpretation and the diagnostic system used. ICD-11 attempts to reduce this problem through one shared ASD category and a more precise description of the current functioning profile.

One important caveat remains: a former Asperger syndrome diagnosis should not be automatically rewritten under a new code without assessing the current picture. ICD-11 requires attention to social communication difficulties, restricted and repetitive patterns of behaviour, adaptive functioning, intellectual development and functional language.

Two core domains of ASD in ICD-11

ICD-11 describes ASD through two basic areas of diagnostic requirements.

The first area covers persistent difficulties initiating and sustaining social communication and social interaction. This may involve difficulty reading social cues, limited reciprocity in conversation, literal understanding of language, problems adapting behaviour to context, difficulty understanding other people's intentions, and difficulty forming and maintaining relationships. This is not a simple "lack of desire for contact", but a different way of processing and using social information.

The second area covers restricted, repetitive and inflexible patterns of behaviour, interests or activities. This may include a strong need for routine, discomfort with change, intense and narrow interests, repetitive movements, attachment to patterns, difficulty flexibly shifting between activities, and atypical responses to sensory stimuli such as sounds, light, touch, smells or textures.

Features from both areas are needed for an ASD diagnosis. Sensory selectivity, shyness, difficulty with eye contact or one intense interest alone is not enough for a diagnosis.

Variants 6A02 - description of intellectual and language functioning profile

ICD-11 specifies ASD through two main dimensions: whether disorder of intellectual development co-occurs and what level of functional language is present. Functional language means the ability to use spoken language, sign language or another communication system for practical communication: expressing needs, wishes, choices, refusal and basic information about oneself. It is therefore not only about the number of words spoken, but about real use of communication in everyday life.

This is an important change from ICD-10: instead of relying mainly on former types and speech development history, ICD-11 describes the person's current functioning profile.

Functional language and speech delay

In ICD-10, a history of speech delay was important for distinguishing former categories, especially childhood autism and Asperger syndrome. ICD-11 shifts the emphasis to the current use of language in practical communication.

This distinction matters. A person may speak a lot but have serious difficulties with dialogue, turn-taking, understanding intentions, language pragmatics and adapting communication to the situation. Another person may use only a small number of words or augmentative communication, yet effectively express needs, choices and refusal. For planning support, it is more useful to ask whether communication works functionally in everyday life, not only whether the person "speaks".

Masking and late diagnosis

ICD-11 notes that in some people ASD features may not be immediately visible because the person compensates for difficulties with great effort. This is especially important when recognising ASD in adults and in people who for years appeared to function adequately in social situations.

ASD is a neurodevelopmental disorder, so its onset falls within the developmental period. This does not mean, however, that difficulties are always recognised in childhood. In some people, symptoms become more visible only when social, educational, occupational or relationship demands exceed compensatory capacities.

Masking means strategies that make autistic features less visible to others. It may include learning conversation scripts, forcing eye contact, imitating peers' behaviour, analysing social situations intellectually rather than intuitively, and hiding sensory overload. From the outside, the person may look "well-functioning", but the cost can be very high: fatigue, withdrawal after contact, anxiety, lowered mood or autistic burnout.

ASD in girls and women

For many years, the classic image of autism was based mainly on observations of boys. In girls and women, ASD may be less stereotypical and therefore harder to recognise. More often described are stronger masking, greater social adaptation, intense interests perceived as more "typical" or socially acceptable, perfectionism, exhaustion after contact, difficulties in friendships and a long-standing feeling of being different.

A girl with ASD may have peer relationships but not always understand their hidden rules. She may intensely analyse others' behaviour, imitate peers' style and prepare conversations in advance. If she speaks fluently, learns well and does not show behaviours stereotypically associated with autism, her difficulties may be attributed to anxiety, shyness, sensitivity or perfectionism. This is one reason ASD is recognised late in some girls and women. Review articles suggest that ICD-11 better captures the heterogeneity of ASD presentations, but diagnosis still requires a careful developmental history and assessment of functioning across contexts.

ASD, disorder of intellectual development and language

One important element of ICD-11 is separating ASD itself from co-occurring disorder of intellectual development. A person can be on the autism spectrum and have average or high intellectual abilities. A person can also have both ASD and disorder of intellectual development. These two areas should be assessed separately.

This approach protects against two errors. The first is assuming that autism always means intellectual disability. The second is attributing all communication difficulties in a person with disorder of intellectual development solely to intellectual level, which may leave ASD unrecognised.

The same applies to language. If language difficulties go beyond what can be expected in ASD alone, a separate assessment of speech and language development is needed. Social communication support does not replace language therapy if an independent language problem is present.

Differential diagnosis: what not to confuse with ASD?

An ASD diagnosis should not be based on isolated features such as difficulty with eye contact, shyness, literalness, strong interests or sensory overload. A similar picture may occur in various clinical and developmental conditions.

ADHD can resemble ASD through social difficulties, impulsivity, emotion regulation problems and sensory overload. In ADHD, the main mechanism concerns attention, impulsivity and activity. In ASD, the core consists of qualitative difficulties in social communication and restricted, repetitive and inflexible patterns of behaviour. Both diagnoses can also co-occur.

Social anxiety can cause avoidance of contact, tension in relationships and difficulty with social exposure. In social anxiety, the person usually understands social rules but fears evaluation, rejection or embarrassment. In ASD, the difficulty is more about intuitive reading of social cues and flexible adaptation of behaviour to context.

CPTSD and developmental trauma can produce withdrawal, hypervigilance, rigidity, avoidance and emotional overload. In differential diagnosis, it is important to ask whether symptoms are linked to traumatic exposure and defensive mechanisms, or whether they have a neurodevelopmental character present since childhood.

Personality disorders can be confused with ASD, especially in adults diagnosed late. Rigidity, interpersonal difficulties, emotional distance or an unusual relational style should not automatically be interpreted as a personality disorder. Developmental history, the presence of features since childhood and the quality of social-communication difficulties are key.

Speech and social communication disorders can resemble ASD, but communication difficulties alone are not enough to diagnose autism. ASD also requires the second area: restricted, repetitive and inflexible patterns of behaviour, interests or activities.

Co-occurrence

ASD often co-occurs with other disorders or developmental difficulties. Common co-occurring problems include ADHD, anxiety disorders, mood disorders, sleep disorders, eating problems linked to food selectivity, disorder of intellectual development, tics, movement disorders and epilepsy.

Recognising co-occurring disorders has major clinical importance. It helps avoid reducing all difficulties to one label and makes support planning more accurate. In some people, co-occurring problems such as anxiety, depression, sleep disorders or ADHD may lower quality of life more than the autistic features themselves.

Limitations and controversies of ICD-11

The new ICD-11 approach is more flexible and better describes the diversity of the spectrum, but it does not remove all diagnostic difficulties. A very broad understanding of ASD may increase diagnostic sensitivity, but it also raises questions about the precision of diagnostic boundaries, consequences for research and access to support. The literature notes that the breadth of symptom combinations in ICD-11 may better capture ASD diversity, but may also make clinical and research clarity harder.

For some people, removing Asperger syndrome as a separate diagnosis may be difficult because the name was part of identity, community language and self-understanding. At the same time, the shared concept of the autism spectrum may make diagnostic communication and support organisation easier, as long as the individual profile is not lost.

The article should therefore avoid two simplifications. The first is: "ICD-11 simplified autism to one label" - incomplete, because ICD-11 adds important specifications of functioning. The second is: "every social atypicality means ASD" - also incorrect, because diagnosis requires persistent features from both core areas, developmental history, differential diagnosis and assessment of co-occurrence.

Summary and when to seek help

ICD-11 brings order to autism diagnosis by replacing former separate categories with one category, autism spectrum disorder (6A02). The diversity of autistic people is not ignored. It is described in a different language: through the current intellectual and language functioning profile, not through historical type labels.

Asperger syndrome is not a separate main diagnosis in ICD-11. The clinical picture formerly described in this way most often falls within 6A02.0, meaning ASD without disorder of intellectual development and with mild or no disorder of functional language. Adult diagnosis is possible and justified if developmental history points to features present since childhood, even if they were masked for years.

The content of this article is educational and does not replace specialist assessment. If difficulties in communication, relationships, behavioural flexibility, sensory regulation or everyday functioning have persisted for a long time and genuinely impair life, the appropriate next step is consultation with a psychiatrist, clinical psychologist or a team specialising in neurodevelopmental diagnostics.

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