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UKCRC Health Research Classification System

Substance misuse and addiction

Advice on health categories

Both smoking and alcohol have their own specific guidance topics relating to misuse and addiction.

Other substances should be classified depending on the nature of the research.

  • All studies of addiction are treated as psychological conditions and should be coded as Mental Health.
  • Any study of substance abuse / misuse that relates to a specific disease or condition should be coded to the appropriate health category:
    • e.g. intravenous drug use and risk of infection should be coded Infection.
  • The Disputed Aetiology and Other health category also includes some types of social services research for specific ‘healthy’ at risk groups that is not relevant to the general population, e.g. young people or minorities at risk of developing substance misuse problems. Note that in these cases Other should only be used if there is no other disease/condition of focus presented.


Advice on research activities

Substance misuse is considered a risk factor for other diseases. Therefore, interventions to reduce substance misuse should be coded as 3 Prevention, even if the person is already misusing. Use 5 Treatment Development or 6 Treatment Evaluation for studies focussed on treatment of an existing substance-misuse-related disease and in cases of secondary prevention.

Additional guidance on differentiating secondary and primary prevention is also available.


Main inclusion criteria

Conditions of unknown or disputed aetiology (such as chronic fatigue syndrome/myalgic encephalomyelitis), or research that is not of Generic Health Relevance and not applicable to the top 19 health categories with specific pathological / physiological determinants.

Advice on health categories

The Disputed Aetiology and Other category is rarely used and should only be used in specific circumstances that cannot be attributed to any of the 19 named health categories or Generic Health Relevance. There are three such circumstances suggested here. Research that does not fall into the preceding 20 health categories or these specified uses of Other should be considered outside of scope for HRCS coding.

(1) Unknown or disputed Aetiology
The most frequent circumstance where coding to Other is appropriate are conditions of unknown or disputed aetiology. Conditions include:

  • Chronic Fatigue Syndrome / Myalgic Encephalopathy / Post-Viral Fatigue Syndrome / Chronic Fatigue Immune Dysfunction Syndrome:   It is not known how these conditions are triggered; some experts have suggested they are a result of a virus but this does not explain why symptoms get worse after the virus has resolved. The aetiology of the condition has not been agreed.
  • Gulf war syndrome/illness:   This is a multi-symptom disorder affecting returning military personnel and civilians from the Gulf war. The condition has long lasting symptoms and has been recognised by the Department of Defence but there is not agreement on the underlying cause or a formal definition of the condition. Note this is a separate condition distinct from Post-traumatic Stress Disorder (PTSD, which should be coded as Mental Health).


(2) Animal Welfare
In general studies of animal welfare should be assigned the Other category. This applies to studies with direct focus on laboratory animals and the use of animals in human health research. The wider field of veterinary research is outside the scope of HRCS.

See the guidance topic on Animal Welfare for further details.

(3) Social Services Research
Not all social services research will be within scope of HRCS. Only social services research with a health relevant component should be classified, and most health-relevant social research will be applicable to the general population and therefore classified under Generic Health Relevance.

However Other also includes some types of social services research focuses on specific ‘healthy’ at risk groups that is not of relevance to the general population. Examples of such research include:

  • Research into services for young people at risk of domestic violence.
  • Research into services for minorities at risk of hate crime.


Official terminology

Full name

Short Name Unique ID
Disputed aetiology and other Other



Related external links

International Classification of Diseases (ICD 10 v2016) – Chapter XVIII:   Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R99)

Main inclusion criteria

Depression, schizophrenia, psychosis and personality disorders, addiction, suicide, anxiety, eating disorders, learning disabilities, bipolar disorder, autistic spectrum disorders and studies of normal psychology, cognitive function and behaviour.


Advice on health categories

Mental Health should be used for all normal cognitive research categorised to 1.2 Psychological i.e. behaviour learning, memory, language, perception etc.

Studies dealing with the brain of individuals with a psychological condition listed in the Mental Health category should be coded as 100% Mental Health and not as Neurological.

Official terminology

Full name of category

Short name Unique ID
Mental health Mental



Related external links

International Classification of Diseases (ICD 10 v2016) – Chapter V:   Mental and behavioural disorders (F00-F99)