Diagnostic criteria for schizophrenia — common mistakes

When evaluating the diagnosis of schizophrenia, always link your points explicitly to reliability and validity. For example, don't just state that Rosenhan's study criticises diagnosis; explain how it demonstrates low validity by showing that clinicians could not distinguish real symptoms from feigned ones. Use specific examples of symptoms, like cultural interpretations of hearing voices, to support your arguments.

Reliability refers to the consistency of a diagnosis. For example, if two different clinicians assess the same patient, will they arrive at the same diagnosis (inter-rater reliability)? Validity refers to the accuracy and meaningfulness of the diagnosis. Does the label of 'schizophrenia' represent a real and distinct medical condition, and does it help predict the course of the illness or response to treatment?

The subtypes were removed because they were found to have low reliability, poor validity, and limited diagnostic stability. Clinicians often disagreed on the subtype, and patients could move between subtypes over time. The DSM-5 replaced them with a dimensional approach, using specifiers to rate the severity of core symptoms, which is considered more clinically useful.

Neither factor works in isolation. The dominant explanation is the diathesis-stress model. This model proposes that individuals may have a genetic predisposition or biological vulnerability (the 'diathesis') to schizophrenia, but the disorder will only develop if the individual is exposed to environmental or psychological stressors, such as family dysfunction, substance abuse, or critical life events.