F84 vs F70
F70 — Mild mental retardation (intellectual disability)
Distinguish a pervasive developmental disorder (F84) from intellectual disability (F70) presenting on its own, using the presence or absence of the qualitative social-interaction/communication/restricted-behaviour triad rather than global cognitive level — a cross-block boundary check, since the two conditions frequently co-occur and can both be coded together when both are genuinely present.
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Show overlap — what both share
Autistic people frequently also have an intellectual disability, and a child with global developmental delay can show reduced social responsiveness or limited language for reasons unrelated to the F84 triad, so a vignette showing global delay alone can be mistaken for pervasive developmental disorder, and vice versa.
Show decisive evidence
- F84 is defined by the qualitative triad — abnormal reciprocal social interaction, abnormal communication, and restricted/repetitive behaviour — assessed relative to the person's own mental age, not by intellectual level alone.
- F70 is defined by significantly subaverage general intellectual functioning together with limitations in adaptive behaviour, without requiring the qualitative F84 triad to be present.
- A person with global cognitive and adaptive limitations, but whose social interaction, communication style, and behaviour are consistent with what would be expected at their own developmental/mental age, favours F70 alone.
- A person showing the qualitative triad — behaviour that is abnormal even relative to their own mental age, not just delayed in step with it — favours F84, whether or not intellectual disability is also present and separately coded.
What weakens F84: Social interaction and communication consistent with the person's own mental age weakens F84 regardless of global cognitive level; qualitative abnormality beyond what mental age would predict weakens a intellectual-disability-only classification.
Show duration / course
Both are developmental in onset; F84's specific subtypes carry their own onset/course requirements (see the F84 category record), while F70 requires onset during the developmental period without a triad-based qualitative requirement.
Show exclusions / context
Global intellectual and adaptive deficits without the qualitative pervasive-triad abnormalities are directed to F70 rather than F84, per the exclusions_distinctions entry on the F84 category record — and the two are not mutually exclusive: both can be coded together when both are genuinely present.
Show information still needed
Whether social interaction, communication, and behaviour are qualitatively abnormal relative to the person's own mental age (pointing to F84, possibly alongside F70), or simply delayed in a manner consistent with that mental age (pointing to F70 alone).
Show the common trap
Assuming that any child with global developmental delay and limited social responsiveness must have a pervasive developmental disorder, without checking whether the observed behaviour is genuinely qualitatively abnormal relative to the child's own mental age, rather than simply delayed in step with it.
Mini challenge — practise this distinction
Apply the discriminating evidence above to a fresh case before checking the full feedback.