Classification and Diagnosis (ICD/DSM)
What the exam tests
Classification items test criterion counting, duration rules, hierarchy and the differences between ICD-11 and DSM-5-TR. You must know when a syndrome is substance-induced, medical or better explained by another disorder.
Core rules
- DSM-5-TR is categorical and criterion-based; ICD-11 is also criterion-based but often uses shorter duration requirements.
- DSM-5-TR schizophrenia requires two or more symptoms, at least one from delusions, hallucinations or disorganised speech, active-phase symptoms for one month and continuous disturbance for six months. ICD-11 schizophrenia requires core symptoms for at least one month.
- Major depressive disorder requires five of nine symptoms for two weeks, including depressed mood or anhedonia, with impairment.
- Mania requires elevated or irritable mood plus increased energy for at least one week or hospitalisation; hypomania requires four days without marked impairment or psychosis.
- Exclude substance effects, medical conditions and schizoaffective disorder before labelling a primary psychotic or mood disorder.
Worked example
A 60-year-old widow has three weeks of sadness, insomnia, weight loss, anhedonia, guilt about not doing enough and reduced function. Grief alone can cause sadness, but pervasive anhedonia plus guilt and functional decline for two weeks supports major depressive disorder. The reasoning is that DSM-5-TR does not exclude depression simply because it follows bereavement; the syndrome and impairment drive the diagnosis.
Traps that cost marks
Do not count symptoms from different episodes. Do not ignore a medical cause such as hypothyroidism or steroid use. Do not use 'atypical' loosely; it refers to mood reactivity, hypersomnia, leaden paralysis and rejection sensitivity. Check whether ICD or DSM duration rules are being tested.