Classification & Assessment in Psychiatry · Paper A
Rating scales: selection, purpose and psychometric properties
Rating-scale vignettes usually hide the answer in two clues: what is being measured and who is doing the rating. A depression stem completed by the patient points toward PHQ-9 or BDI; the same construct rated by a trained clinician points toward HAM-D or MADRS. The scale is wrong if either the construct or the rater does not match.
Scales measure severity, screen for symptoms, or track change over time; they do not make a diagnosis by themselves. HAM-D (Hamilton Depression Rating ScaleA clinician-administered scale that scores the severity of depressive symptoms.Read more →) and MADRS (Montgomery-Asberg Depression Rating ScaleA clinician-administered scale designed to be sensitive to change in depressive symptoms during treatment.Read more →) are clinician-rated depression scales, while PHQ-9 (Patient Health Questionnaire-9) and BDI (Beck Depression InventoryA self-completed questionnaire that scores the severity of depressive symptoms.Read more →) are self-report depression measures. The Young Mania Rating ScaleA clinician-administered scale that scores the severity of manic symptoms.Read more → is used for manic symptoms. PANSSPositive and Negative Syndrome Scale, a scale used to score the severity of psychotic symptoms.Read more → (Positive and Negative Syndrome Scale) rates positive, negative, and general symptoms in schizophreniaA long-term mental illness involving episodes of psychosis such as hallucinations and delusions.Read more →. Y-BOCS (Yale-Brown Obsessive Compulsive Scale) rates obsessive-compulsive symptom severity. The revised Clinical Institute Withdrawal Assessment for Alcohol scale is used in alcohol withdrawal to guide symptom-triggered benzodiazepine treatment. Movement-disorder scales test a different construct: AIMSAbnormal Involuntary Movement Scale, a scale used to score unwanted movements caused by antipsychotic drugs.Read more → (Abnormal Involuntary Movement Scale) screens abnormal involuntary movements and tardive dyskinesia, Simpson-Angus assesses drug-induced parkinsonism, and Barnes rates akathisiaAn inner restlessness and urge to keep moving, a common side effect of antipsychotic drugs.Read more →.
A rating scale is only useful if it is matched to the right construct AND the right rater, and exam vignettes are built almost entirely around testing that match. A self-report questionnaire completed by the patient measures something subtly different from a clinician-administered interview scale measuring the exact same illness, because self-report captures the patient's own perception while a clinician-rated tool captures the clinician's structured observation. Choosing the wrong scale for a described scenario is one of the most common ways marks are lost in this topic, which is why "who fills it in" is treated as just as important a clue as "what condition is being measured."
A rating scale is a standardised, structured tool that assigns a numeric score to the severity of a symptom or a set of symptoms, allowing that severity to be tracked, compared, and monitored over time. It is not a diagnostic test on its own: a high score suggests severity, but the diagnosis itself still rests on full clinical assessment.
The single most tested distinction is clinician-rated versus self-rated (also called patient-rated or self-report) scales for the SAME condition. For depression specifically, the (HAM-D) and the Montgomery-Åsberg Depression Rating Scale (MADRS) are both clinician-rated, completed by a trained assessor during a structured interview, while the PHQ-9 (Patient Health Questionnaire-9) and the Beck Depression Inventory are both self-rated, filled in by the patient alone. For example, imagine a vignette describing a patient completing a short questionnaire by themselves in a GP waiting room before their appointment, that detail alone should point to the PHQ-9 or Beck inventory, never to the Hamilton or MADRS, regardless of what else the stem says about severity.
Scales exist because clinical impressions of severity are inherently subjective and hard to compare across time or between clinicians. A numeric score turns "this patient seems a bit better" into a measurable, comparable number, which matters enormously for tracking treatment response, deciding when a treatment has genuinely failed (relevant to treatment-resistant depression), and for research. Different constructs (depression, , psychosis, obsessive-compulsive symptoms, withdrawal, or abnormal movements) each need a purpose-built tool, because a single generic "how unwell are you" scale cannot capture the specific symptom pattern of, say, mania versus psychosis.
For depression: HAM-D and MADRS are clinician-rated; PHQ-9 and the Beck inventory are self-rated. For (the over-elevated "high" phase of bipolar disorder), the Young Mania Rating Scale is the standard clinician-rated tool. For , PANSS (the Positive and Negative Syndrome Scale) is clinician-rated and separates positive symptoms (, ), negative symptoms (, apathy), and general psychopathology into distinct sub-scores. For (obsessive-compulsive disorder), the Yale-Brown Obsessive Compulsive Scale (Y-BOCS) rates the severity of and separately, then combines them into a total score. For alcohol withdrawal, the CIWA-Ar (Clinical Institute Withdrawal Assessment for Alcohol, revised) is used repeatedly at the bedside to guide symptom-triggered benzodiazepine dosing during detoxification: a stem describing dosing that changes based on repeated symptom scores during an inpatient detox is a textbook CIWA vignette. Cognitive screening uses a different family entirely: the MMSE () and MoCA () are brief, clinician-administered cognitive screens, not mood or psychosis scales.
This concept is about measurement tools rather than a disease process, so "diagnosis" here really means correctly identifying, from a vignette, which scale is being described. The two clues to extract every time are the construct (which illness or symptom cluster is being measured) and the rater (patient self-report versus a trained clinician administering a structured interview); both usually need to match the scale named in the correct answer.
Movement disorders linked to antipsychotic treatment have their own dedicated scale family, separate from the mood and psychosis scales above, and NICE guidance on monitoring antipsychotic side effects (alongside the Maudsley Prescribing Guidelines) recommends their routine use. The (Abnormal Involuntary Movement Scale) is purpose-built to screen for tardive dyskinesia in patients on long-term antipsychotics. The Simpson-Angus Scale instead assesses drug-induced Parkinsonism (bradykinesia, rigidity, tremor), and the Barnes Rating Scale rates akathisia, a distressing inner restlessness with an urge to move. Using the correct scale at the correct monitoring interval is itself part of good antipsychotic prescribing practice, not an optional extra.
Whenever a stem describes WHO is completing a scale, treat that as a deliberate clue, not incidental detail. "Completed by the patient in the waiting room" always means a self-rated tool; "scored by the assessing psychiatrist during interview" always means a clinician-rated tool, even when both options measure the identical underlying construct.
Always extract two clues from a rating-scale vignette, the construct measured and who does the rating, and match both, since scales measure severity and change but never replace a full clinical diagnosis.