Lecture 33: Debate dimensional vs categorical Teifon Davies

Question 1

Provide some recent events involved in the debate of approaching psychiatric classification in categorical and dimensional ways

Answer 1

2005 - Widiger & Samuel challenged the APA - are there diagnostic categories or dimensions?

2007 - DSM-V taskforce wanted to approach the latest update to produce a fully dimensional approach to diagnosing mental health conditions

2011 - the taskforce conceded a fully dimensional approach was not possible

2013 - DSM-V published with a mixture of categories and dimensions (mainly categories)

Question 2

Why is classification needed?

Answer 2

• Respect
• Validity & reliability
• Standardisation/definition
• Moral duty –> if X condition exists then we as society should do Y
• Overcome cultural differences
• Communication - for patients/research - to aid decision making processes and use of resources
• Administrative reasons - i.e. public health

Question 3

Outline the goals of an ideal classification system?

Answer 3

Reliability
- Both intra-rater and inter-rating - as an important topic we need to get consistent results

Validity
- Face validity - subjectively when looking at classification system it reflects the underlying variable/diseases

• Construct validity - based on test result, classification - research/theory support this as a correct classification
• Content validity - the classification system or test is comprehensive to include all details of the variable/disease

Stability & flexibility
- Not decline or become unhelpful overtime but also be able to include new research information into the system

Usability & trainability

• Not too difficult for practitioners to interact with
• Become easy enough to develop clinicians to be able to use

Usefulness
- Functions to classify something that needs classifying

Resource efficiency
- Not intensive to work out how to clasificy

Question 4

Describe the disease and illness debate with regards to how mental disorders are classified?

Answer 4

Disease (objective) - illness (subjective)

Disease - structural and/or functional abnormalities

• Disease definition is formed on knowing normal/abnormal or inferring
• However disease cannot explain the illness - not sufficient or necessary

Disease and illness definitions are influenced by social/political factors

Question 5

Outline some hot takes commenting on how brain and mind relate to each other

Answer 5

Materialism/physicalism

• Only disorders of the brain exist
• Mind comes from that - only physical disorders

Biological naturalism

• Mind is the function of the brain - the realising of the brain is the mind
• Disorders or the brain produce disorders of the mind - mental disorders are secondary

Dualism/epiphenomenalism

• Mind and brain are separate - distinct to each other but they may interact
• Mind are brain have separate but interlinked disorders
• Mind may be primary
• Descartes dualism - that the mind would continue to function without the brain although in some instances they interact

Question 6

Compare the DSM-IV, DSM-V, ICS-10 and ICD-11 classification systems with regards to if they use categorical or dimensional approaches to diagnosis

Answer 6

DSM-IV - categorical:
- Multi-axial - each axis is a category (affective axis I / personality axis II)

DSM-V:

• Categorical
• Claims to use dimensions but little influence

ICD-10:
- Categorical

ICD-11:

• Categorical
• Rather than operationalised checklists there are narratives for which clinicians need to apply

Question 7

Describe the features of categorical and dimensional approaches to diagnosis

Answer 7

Categorical:

• Clinical features are defined a priori
• Symptoms and signs assigned to categories
• Mutually exclusive categories - jointly exhaustive
• Diagnosis on specific categories –> distinct disorders
• Binary all-or-none and yes or no

Dimensional:

• Clinical features are defined a priori
• These features are placed on a continuum or dimension
• Diagnosis is dependent on degree of severity
• Continuous scale

Question 8

Outline some pros/cons of dimensional vs categorical approaches to diagnosis

Answer 8

Dimensional
- Pros –> validity in clinical practice, incorporates a lot of information for each diagnosis, wide range of factors are accepted to cause a disease - not just symptoms, flexible and adaptable over time

• Cons –> may find reliability tricky, where is the threshold set, hard to communicate to patients/clinicians, may actually delay disease specific treatment research

Categorical:
- Pro’s –> standardised, practical and reliability, claims validity, helps communicate and can aid research towards specific diseases

• Con’s –> validity difficulties and some reliability issues, how are symptoms defined, co-morbidity and symptom overlap, stigma, not flexible to incorporate new information (a whole new classification system would be needed)

Question 9

Define accuracy and precision

Answer 9

Accuracy is how close the estimates are to real value

Precise is degree to which estimates are to each other