Diagnosis of mental disorders: definitions of abnormality, the DSM and ICD classification systems, reliability and validity of diagnosis, and cultural and ethical issues.

What this dot point is asking

Edexcel wants you to define abnormality, describe the DSM and ICD classification systems, evaluate the reliability and validity of diagnosis, and discuss cultural and ethical issues, using Rosenhan as the key study. This underpins every disorder in clinical psychology, so it links to schizophrenia, depression and the medical model.

The answer

Defining abnormality

Each definition has limits. Statistical infrequency cannot distinguish desirable rarity (high IQ) from undesirable rarity (depression). Deviation from social norms is culturally and historically relative (homosexuality was once classified as a disorder). Failure to function can mislabel non-conformists, and Jahoda's ideal mental health is so demanding that almost everyone would be classed abnormal. Most clinicians therefore use classification systems rather than a single definition.

Classification systems: DSM and ICD

Reliability and validity

Rosenhan (1973): On Being Sane in Insane Places

Rosenhan sent eight healthy pseudopatients to psychiatric hospitals, each claiming to hear a voice saying "empty", "hollow" and "thud". All were admitted, most diagnosed with schizophrenia. Once inside, they behaved normally, yet staff reinterpreted normal behaviour (note-taking) as symptoms. They were discharged after an average of 19 days with schizophrenia "in remission". In a follow-up, a hospital told that pseudopatients might be sent rejected many genuine patients as fakes, though Rosenhan had sent none. The study showed the stickiness of labels and challenged the validity of diagnosis: clinicians could not reliably distinguish the sane from the insane.

Cultural and ethical issues

Diagnosis can show cultural bias when behaviour normal in one culture (hearing the voice of an ancestor) is judged abnormal by the standards of another (an imposed etic), which contributes to the over-diagnosis of schizophrenia in some ethnic minority groups. Ethical issues arise from labelling: a diagnosis carries stigma, can trigger a self-fulfilling prophecy, and the consequences of misdiagnosis (wrong or harmful treatment) can be severe.

Evaluation (GRAVE)

• Generalisability. Rosenhan's study was conducted in 1970s American hospitals, so its findings may not generalise to modern, criteria-based practice with the DSM-5.
• Reliability. Modern classification systems have raised inter-rater reliability through operationalised criteria, but agreement is still imperfect, especially for disorders with overlapping symptoms.
• Application. Shared classification allows clinicians worldwide to communicate, target treatments and conduct comparable research, a major practical benefit.
• Validity. Comorbidity, symptom overlap and Rosenhan's findings all suggest the categories may not map onto distinct underlying disorders.
• Ethics. Labelling produces stigma and self-fulfilling prophecies; Rosenhan's covert method also deceived staff, raising consent issues, though it exposed an important problem.

Examples in context

Example 1. Rosenhan's labelling effect in detail. The most cited finding of Rosenhan (1973) is not just that the pseudopatients were admitted, but that the schizophrenia label changed how all their subsequent behaviour was read. Normal note-taking was recorded as "patient engages in writing behaviour", and ordinary biographical history was reframed to fit the diagnosis. This demonstrates the power of a diagnostic label to bias clinical perception, a key ethical argument against premature or careless diagnosis and a real consideration in modern psychiatry, where diagnoses can follow a person through records for years.

Example 2. Cultural bias and the over-diagnosis of schizophrenia. Studies in the UK and US have repeatedly found that people from some Black and minority ethnic groups are diagnosed with schizophrenia at higher rates than White patients with similar symptoms. Explanations include clinicians applying an imposed etic (interpreting culturally normal expressions of distress as symptoms) and language and trust barriers in the clinical interview. This is a concrete example of how cultural bias undermines the validity and fairness of diagnosis and why the DSM-5 added a cultural formulation interview to prompt clinicians to consider cultural context.

Try this

Q1. Outline two ways of defining abnormality. [4 marks]

• Cue. Statistical infrequency (behaviour statistically rare in the population) and deviation from social norms (behaviour that breaks society's accepted rules).

Q2. Explain what Rosenhan's study suggests about the validity of diagnosis. [3 marks]

• Cue. Healthy pseudopatients were admitted and diagnosed, and normal behaviour was reinterpreted as symptoms, suggesting diagnosis lacks validity and is heavily influenced by labelling.

Q3. Assess the reliability and validity of the diagnosis of mental disorders. [8 marks]

• Cue. Argue reliability has improved with operationalised DSM/ICD criteria but is still imperfect; argue validity is weaker, citing Rosenhan, comorbidity, symptom overlap and cultural bias; conclude diagnosis is more reliable than valid.