The Concept of Psychosis, Psychotic Symptoms, and Psychotic Disorders

1. Overview & Epidemiology

Psychosis = loss / disturbance of reality-testing. This is the essence of the concept (PSY - 3.9): the patient can no longer reliably distinguish internal experience from external reality, and the false beliefs/perceptions are held with conviction despite contradictory evidence.
Psychosis is a syndrome, NOT a single diagnosis. It is a cross-sectional state that occurs across many disorders — schizophrenia spectrum, mood disorders (psychotic depression, manic psychosis), substance use, and organic/medical conditions.
The classic descriptive division (Gajdos, Schizophrenia):
- Positive (productive) symptoms — delusions, hallucinations, formal thought disorder. "Added on" experiences, the manifestations of psychosis.
- Negative (deficit) symptoms — flat/blunted affect, alogia (poverty of speech), anhedonia, avolition. The loss of normal traits.
- Disorganization syndrome — chaotic speech, thought and behaviour (third grouping).
Reality-testing vs insight: in psychosis reality-testing fails and insight is typically lost — the patient does not recognise the symptoms as products of illness (contrast: an obsessional patient with OCD usually retains insight).

Schizophrenia: lifetime prevalence ≈ 1% (1 in 100); occurs equally in both sexes; onset earlier in men (peak 20–28 y in males, 26–32 y in females). Higher incidence in those born/raised in urban areas of industrialised nations (Gajdos).
Any psychotic disorder (spectrum): roughly 3% lifetime.
Brief psychotic disorder: rare; more common in women and in personality-disorder patients; often post-partum or after a major stressor.
Delusional disorder: uncommon (~0.2% lifetime); later onset (middle/late adulthood) than schizophrenia; persecutory type is the commonest.