9990 · 1.1.1
Diagnostic criteria for schizophrenia — FAQ
Frequently asked questions for 9990 Diagnostic criteria for schizophrenia. Direct answers first, then deeper explanation — then practise with marking.
What is the difference between reliability and validity in diagnosis?
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?
Why were the subtypes of schizophrenia (e.g., paranoid, catatonic) removed from the DSM-5?
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.
Is schizophrenia caused by genetics or the environment?
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.