4 Classification and assessment in psychiatry4.2 Classificatory systems
4.2.2 WHO classification of impairments, disabilities and handicaps
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Written by Resident Doctor Committee · Published
Diagnosis and functioning
Diagnosis identifies a condition, while functioning describes what someone can do and what support they need. The World Health Organization (WHO) classifies both.
Support can enable participation despite severe impairment, and barriers can exclude someone with mild impairment, so need is assessed individually.
The ICIDH (1980)
The International Classification of Impairments, Disabilities and Handicaps (ICIDH) separated three consequences of disease.
Term | Level | Definition | Example |
|---|---|---|---|
Impairment | Organ or system | Loss or abnormality of psychological, physiological or anatomical structure or function | Anhedonia in depression, amnesia in dementia |
Disability | Person doing tasks | Restriction or lack of ability to perform an activity within the range considered normal | Cannot cook, take medication or travel alone |
Handicap | Person in society | Disadvantage limiting a role normal for that person, given age, sex and social and cultural factors | Unemployment, loss of tenancy, isolation |
The sequence of disorder, impairment, disability and handicap is not reliably linear: adaptations may prevent disability, and stigma may restrict participation despite few symptoms.
Unemployment and isolation can also worsen the illness.
Handicap is historical terminology, replaced by participation restriction, and is not used in current clinical descriptions.
The ICIDH overemphasised individual deficits and a stable linear process, gave too little weight to fluctuating conditions, social attitudes and environmental barriers, and used stigmatising terms.
The ICF (2001)
The International Classification of Functioning, Disability and Health (ICF) describes functioning as an interaction between health and context.
Component | Problems are called | Content | Example |
|---|---|---|---|
Health condition | The diagnosis | Disorder coded in the International Classification of Diseases | Bipolar affective disorder |
Body functions and structures | Impairments | Physiological and psychological functions, and body parts | Disturbed sleep regulation, poor attention |
Activities | Activity limitations | Execution of tasks by the person | Difficulty budgeting |
Participation | Participation restrictions | Involvement in life situations | Not working, withdrawal from family roles |
Environmental factors | Barriers or facilitators | Physical, social and attitudinal context | Employer discrimination (barrier), workplace adjustments (facilitator) |
Personal factors | Acknowledged, not classified | Age, coping, education, culture | Work history |
The components influence each other, so changing the environment can reduce disability without changing the impairment.
The ICF applies to everyone's functioning rather than defining a separate disabled minority.
Qualifiers grade problems as none, mild, moderate, severe or complete.
Capacity and performance
Capacity is ability in a standardised environment; performance is what the person does in their actual environment.
The gap between them shows barriers and support needs: someone who cooks in an occupational therapy kitchen but not at home may need equipment, money, prompting or company.
Clinic assessment cannot establish everyday performance, so find the reason for the gap before prescribing skills training.
Psychiatric examples
Presentation | Impairment | Activity limitation | Participation restriction | Adjustment |
|---|---|---|---|---|
Depression | Anhedonia, retardation | Starting tasks, self-care | Sickness absence | Phased return |
Psychosis | Executive function, reduced volition | Budgeting, transport | Unemployment, loss of tenancy | Supported employment with a job coach |
Dementia | Episodic memory, praxis | Cooking, money | Loss of driving | Cueing, assistive technology |
Autism | Sensory sensitivity, insistence on sameness | Unexpected change, noisy settings | Exclusion from mainstream school | Predictable routine, written instructions |
Symptom improvement alone may leave activity limitations and participation restrictions, so treatment, rehabilitation and environmental change are combined.
Assessing function
Combine the person's goals and account with observation and, with consent or justification, collateral information.
Depression and cognitive impairment can distort self-estimates, but the direction and extent vary.
Observe tasks in the usual setting where possible, and record strengths, assistance used and the environment assessed.
Standardised daily living scales help with monitoring but cannot replace an individual description.
Special educational needs plans
Statements of special educational needs are historical in England, replaced by Education, Health and Care (EHC) plans under the Children and Families Act 2014. Wales has a separate system.
A parent, young person or professional can request assessment without a diagnosis, and the local authority decides.
Diagnosis and educational need are distinct: some diagnosed children need no plan, while others need provision before any diagnosis.
Plans should state provision specifically, such as weekly individual speech and language therapy rather than "access as appropriate", and are reviewed at least annually.
The psychiatric report gives accurate clinical and functional evidence, including risks and strengths, rather than an unsupported label to obtain support.