Schizophrenia

Schizophrenia is diagnosed from a sustained pattern of psychosis and functional change, not from hallucinations alone. DSM-5/DSM-5-TR criteria used in Canadian practice require at least two characteristic symptoms—delusions, hallucinations, disorganised speech, grossly disorganised or catatonic behaviour, or negative symptoms—for a significant part of one month, with at least one symptom being delusions, hallucinations, or disorganised speech. Continuous disturbance must persist for at least six months, and functioning must be markedly impaired. The time course helps distinguish schizophrenia from brief psychotic conditions, mood disorders with psychotic features, substance effects, and medical causes. A useful clinical model is dysregulated dopamine signalling: excess mesolimbic activity contributes to positive symptoms, while reduced mesocortical activity contributes to negative and cognitive symptoms. Glutamatergic NMDA-receptor dysfunction may also contribute. Most antipsychotic treatment therefore targets dopamine D2 signalling, but medication is only one part of care. Acute treatment uses collaborative antipsychotic monotherapy at the lowest effective dose; psychosocial interventions, family support, suicide-risk assessment, and relapse prevention continue after the crisis settles. Following a first episode, maintenance treatment usually continues for at least 18 months to 2 years before...