Classification & Diagnosis

Schizophrenia

A severe mental disorder characterised by disturbances in thought, perception and emotion.

ICD-10 classification

Requires two or more symptoms including negative symptoms for diagnosis.

DSM-5 classification

Requires at least one positive symptom such as delusions or hallucinations.

Positive symptoms

New experiences added to normal functioning such as hallucinations.

Negative symptoms

Loss of usual abilities such as speech poverty or avolition.

Hallucinations

Sensory experiences without external stimuli, often auditory.

Delusions

Firmly held false beliefs resistant to logic, such as persecution.

Disorganised speech

Incoherent or fragmented communication reflecting thought disorder.

Speech poverty

Reduced quality or amount of speech; a negative symptom.

Avolition

Reduced motivation and inability to begin or sustain goal-directed behaviour.

Reliability of diagnosis

Consistency of diagnosis across time and clinicians.

Inter-rater reliability

Agreement between different clinicians diagnosing the same patient.

Cheniaux study

Two psychiatrists gave different schizophrenia diagnoses using DSM and ICD; shows poor reliability.

Validity of diagnosis

Whether schizophrenia is a genuine, distinct disorder.

Criterion validity

Agreement between different classification systems.

Co-morbidity

Two or more disorders occurring together, complicating diagnosis.

Co-morbidity example

Schizophrenia often co-occurs with depression or substance abuse.

Symptom overlap

Different disorders share symptoms, reducing diagnostic accuracy.

Symptom overlap example

Schizophrenia and bipolar disorder both show hallucinations.

Gender bias in diagnosis

Males more likely diagnosed due to stereotypes and clinician expectations.

Culture bias in diagnosis

African-Caribbean individuals more likely to be diagnosed in UK due to misinterpretation of behaviour.

Rosenhan study

Showed lack of validity; psychiatrists could not distinguish sane from insane in hospitals.

Overdiagnosis concern

Cultural differences misinterpreted as symptoms.

Underdiagnosis concern

Women with high-functioning symptoms less likely to be diagnosed.

Labelling effects

Diagnosis can lead to stigma and self-fulfilling prophecy.