Diagnosis and Classification

Question 1

Prevalence

Answer 1

Serious mental disorder affecting 1% of the population. More common in males, city-dwellers and lower socio-economic groups.

Question 2

Diagnosis

Answer 2

Diagnosis and classification are interlinked. To diagnose a specific disorder, we need to be able to distinguish one disorder from another. Classification - identify symptoms that go together = a disorder.
Diagnosis - identify symptoms and use classification systems to identify the disorder.

Question 3

ICD-10 and DSM-5

Answer 3

There are two main classification systems in use:
DSM-5 - one positive symptom must be present (delusions, hallucinations or speech disorganisation).
ICD-10 (V11 published but not used for diagnosis until 2022) - two or more negative symptoms are sufficient for diagnosis (avolition or speech poverty).

Question 4

positive symptoms

Answer 4

additional experiences beyond those of ordinary existence.
Hallucinations - Unusual sensory experiences that have no basis in reality or distorted perceptions of real things. Experienced in relation to any sense. For example, hearing voices or seeing people who aren’t there.
Delusions - Beliefs that have no basis in reality - make a person with schizophrenia behave in ways that make sense to them but are bizarre to others. For example, beliefs about being a very important person or the victim of a conspiracy.

Question 5

Negative Symptoms

Answer 5

oss of usual abilities and experiences.
Speech poverty - A reduction in the amount and quality of speech. May include a delay in verbal responses during conversation. DSM emphasises speech disorganisation and incoherence as a positive symptom.
Avolition - Severe loss of motivation to carry out everyday tasks. Results in lowered activity levels and unwillingness to carry out goal-directed behaviours.

Question 6

A03:One strength of the diagnosis of schizophrenia is good reliability.

Answer 6

A reliable diagnosis is consistent between clinicians (inter-rater) and between occasions (test-retest). Osorio et al (2019) report excellent reliability for schizophrenia diagnosis (DSM-5) inter-rater agreement of +97 and test-retest reliability of +92.
This means that the diagnosis of schizophrenia is consistently applied.

Question 7

A03:One limitation of the diagnosis of schizophrenia is comorbidity with other conditions

Answer 7

If conditions often co-occur then they might be a single condition. Schizophrenia is commonly diagnosed with other conditions. For example, Buckley et al (2009) concluded that schizophrenia is comorbid with depression (50% of cases), substance abuse (47%) or OCD (23%).
This suggests that schizophrenia may not exist as a distinct condition.

Question 8

A03:A further limitation of diagnosis of schizophrenia is low validity.

Answer 8

Criterion validity involves seeing whether different procedures used to assess the same individuals arrive at the same diagnosis. Cheniaux et al (2009) had two psychiatrists independently assess the same 100 clients. 68 were diagnosed with schizophrenia with ICD and 39 with DSM.
This means that schizophrenia is either over- or under- diagnosed, suggesting the criterion validity is low.

Question 9

A03: (counter) However, in the Osorio study there was excellent agreement between clinicians using different procedures both derived from the DSM system.

Answer 9

This means that criterion validity for schizophrenia is good provided it takes place within a single diagnostic system.