Category · F70-F79 block
F73 — Profound mental retardation
Terminology note: ICD-10's own term for this block is "mental retardation." Modern clinical and educational usage prefers "intellectual disability" (used in DSM-5 and in ordinary clinical practice since the mid-2010s), and ICD-11 has renamed and relocated this entire classification territory to "disorders of intellectual development." This page keeps ICD-10's actual code and official title for classification accuracy, and uses person-first language throughout ("a person with an intellectual disability"), never a label standing in for the person.
What is this category?
F73 is the far end of the same dual-criteria scale, at an approximate IQ range where support needs are pervasive and continuous across every area of daily living, requiring the same careful confirmation — rather than assumption from severity of presentation alone — as every other grade in this block.
Core diagnostic concept
F73 requires the same dual criteria as every other grade — significantly subnormal intellectual functioning and a matching adaptive-functioning deficit, with developmental onset — at an approximate IQ range under 20. Support needs are pervasive and continuous, and associated motor, sensory, or other physical impairments are common, though, as with F72, the classification itself still turns on the same intellectual/adaptive dual criteria rather than on the presence of a physical impairment alone.
Key diagnostic features
- Approximate IQ range under 20
- The lowest approximate range in this block's severity scale.
- Pervasive, continuous support needs
- Support needs typically span every area of daily living, continuously.
- Associated impairments common
- Motor, sensory, or other physical impairments are common at this grade, though not themselves the classification criterion.
- Onset during the developmental period
- Present from early infancy, as with every grade in this block.
How to weigh evidence
These learning labels are teaching aids, not official ICD-10 terminology (see Sources and Method).
- supports A confidently completed assessment placing intellectual functioning in the approximate profound range, together with pervasive, continuous support needs across every daily-living domain.
- consistent not decisive The presence of a severe associated physical impairment alone, without independent confirmation of the intellectual/adaptive picture.
- raises alternative A picture where an associated impairment specifically prevented a confident assessment — this points toward F78, the same logic applied at F72's boundary.
- contradicts or weakens Support needs that are actually less pervasive than a profound-range picture would suggest.
- missing and necessary to ask Whether a confident assessment was actually achieved, given how commonly an associated impairment is present at this grade.
Diagnostic boundary
F73 is distinguished from F72 by the same dual criteria one threshold further, and from F78 by exactly the same distinction drawn at F72's own boundary: whether assessment was actually achievable, not simply how severe the overall presentation looks.
Full comparisons:
Duration and course
Minimum duration: Onset during the developmental period, as with every grade in this block.
Course: A pervasive, continuous, lifelong pattern of support need.
Included presentations
- A confidently completed assessment placing intellectual functioning in the approximate profound range, with pervasive, continuous support needs across every daily-living domain.
Exclusions and distinguishing presentations
| If this is true instead… | Consider | Why |
|---|---|---|
| Support needs and intellectual functioning more consistent with the severe range | F72 | The dual criteria, applied at the severe threshold, may instead support F72. |
| Grading specifically made difficult by an associated sensory, physical, or behavioural impairment | F78 | F78 is reserved for a confounded assessment, exactly as at F72's own boundary. |
Four-character subtypes (orientation)
As with every category in this block, the fourth character records behavioural impairment independently of the severity grade itself.
- F73.0 — No, or minimal, impairment of behaviour
- Behaviour does not require particular attention or treatment beyond the intellectual disability itself. (in_depth)
- F73.1 — Significant impairment of behaviour, requiring attention or treatment
- A behavioural disturbance (e.g. aggression, self-injury) significant enough to need its own dedicated attention, independent of the intellectual disability grade itself. (in_depth)
- F73.8 — Other impairments of behaviour
- A behavioural picture not fitting the other listed states. (taught for orientation only, not separately assessed in this pilot)
- F73.9 — Without mention of impairment of behaviour
- No information given about whether a behavioural impairment is present. (taught for orientation only, not separately assessed in this pilot)
External causes to check first
Categories in this block require that the disturbance is not better explained by another external cause listed below. These short capsules are reminders, not full teaching modules.
Boundary capsule — The dual criteria and grading logic across F70-F79
A shared reasoning check for every category in this block: none of F70-F73 can be supported by an IQ score alone, none of them can be supported by an adaptive-functioning impression alone, and the severity grade (F70-F73) is a separate question from both the behavioural-impairment fourth character and from whether enough information exists to grade at all (F78 versus F79).
What to check:
- Both criteria, together: is there evidence of both significantly subnormal general intellectual functioning (an approximate IQ range) AND a matching concurrent deficit in adaptive functioning (communication, self-care, home living, social and community skills)? Either one alone, without the other, does not support an F70-F73 classification.
- Onset: has the pattern been present since the developmental period (conventionally, before adulthood), rather than appearing as a decline from a previously typical baseline later in life? A later, datable decline points toward an acquired dementia (F00-F03), not toward this block, however similar the resulting scores look.
- Severity grade versus behavioural-impairment axis: is the question 'how subnormal is intellectual and adaptive functioning' (F70 mild, F71 moderate, F72 severe, F73 profound) being kept separate from the independent fourth-character question 'is there also a significant behavioural impairment requiring its own attention or treatment' (.0-.9)? A significant behavioural impairment does not, by itself, make the severity grade any more or less severe.
- F78 versus F79: when a case cannot be graded into F70-F73, is that because grading is specifically confounded by an identifiable associated sensory, physical, or behavioural impairment that makes standard assessment difficult (points toward F78), or because there is genuinely insufficient information available to grade at all, with no such confound identified (points toward F79)? These are two different reasons for not grading, not interchangeable labels for 'unclear.'
A full standardized cognitive and adaptive-functioning assessment by a qualified professional, which is outside this capsule's scope and is needed before any of these classifications is used in real clinical, educational, or support-planning practice.
Common learner errors
Worked example — profound grade confirmed, not assumed
A 4-year-old requires continuous support and supervision across every daily activity. Despite an associated motor impairment, a specialist team completes an adapted developmental assessment without the impairment preventing a confident result, placing his general intellectual functioning in the approximate profound range.
- Step 1 — Check whether assessment was actually achievable: a specialist team completed an adapted assessment without the associated impairment preventing a confident result.
- Step 2 — Check the intellectual-functioning evidence: the approximate profound range (IQ under 20).
- Step 3 — Check the adaptive-functioning picture: continuous support needed across every domain.
- Conclusion — Because a confident assessment was actually completed despite the associated impairment, F73 is supported here rather than F78, which would apply only if the impairment had actually prevented confident grading.
Interactive practice
- Type A Profound and pervasive support needs Recognition / application · Foundation
- Type B One test score, no other information Boundary discrimination · Transfer
Retrieval prompts
Try answering each of these from memory before revealing where to check. Nothing you think or type here is sent or saved anywhere.
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State the approximate IQ range associated with F73.
Reveal answer location
Check Duration and course, Diagnostic boundary, or the rapid revision card below — the cue you need is one of those, in this category's own already-authored wording.
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Explain the one factor that would shift this presentation from F73 to F78 instead.
Reveal answer location
Check Duration and course, Diagnostic boundary, or the rapid revision card below — the cue you need is one of those, in this category's own already-authored wording.
These self-checks are a personal study aid only, visible to you on this page for this visit — they are not stored and do not affect your mastery dimensions.
Rapid revision card
F73: The same dual criteria as every other grade, at an approximate IQ range under 20, with pervasive, continuous, lifelong support needs.
Decisive boundary cues:
- A confidently completed assessment at this range -> weighs toward F73.
- An assessment actually confounded by an associated impairment -> weighs toward F78 instead.
- A less pervasive support-need picture -> weighs back toward F72.
Duration/course: Onset during the developmental period, as a pervasive, continuous, lifelong pattern.
Nearest alternatives: F72, F78
Common mistake: Assuming the profound grade from the severity of an associated physical impairment alone, rather than from a confidently completed intellectual/adaptive assessment.
Retrieval prompt: What confirms that assessment was actually achievable here, rather than confounded?
(or use your browser's print function) Open full-page printable revision view →
Related glossary terms
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Adaptive functioning
The practical skills a person uses to meet the everyday demands of independent living — communication, self-care, home living, social skills, use of community resources, self-direction, and similar domains — assessed relative to what is typically expected at a person's age and cultural context. A concurrent deficit in adaptive functioning, alongside subnormal intellectual functioning, is one of the two criteria required for an intellectual disability classification (F70-F73); intellectual functioning alone is never sufficient.
Source basis
WHO ICD-10 international classification structure and code/title (ICD-10 Browser, 2019 English release).
Original educational synthesis, informed by general published clinical-education understanding of ICD-10 F70-F79; no verbatim CDDG or DCR text is reproduced. See Sources and Method for the full policy.
Last reviewed: 2026-09-17. Full policy: Sources and Method.
Educational resource only. This page and its cases teach ICD-10 classification reasoning using fictional scenarios. It does not diagnose real people and should not be used to assess yourself or anyone else. Intellectual disability is not the person — every person with an intellectual disability deserves the same dignity and respect as anyone else. If you are concerned about a child's development, or about an adult's intellectual or adaptive functioning, please speak with a qualified professional for assessment and support.