What is schizophrenia and how common is it?
Schizophrenia is a chronic psychotic disorder with three symptom groups: positive symptoms (hallucinations, delusions, disorganised speech, disorganised or catatonic behaviour), negative symptoms (reduced motivation and emotional expression) and cognitive impairment (executive function, memory, processing speed). It affects about 1% of people over a lifetime and is among the top ten causes of disability worldwide.
Onset: in men the peak incidence is in the early twenties; in women it comes later in the twenties, with a slower decline. Men also tend to have poorer premorbid functioning, more prominent negative symptoms and more substance use.
What are the DSM-5-TR criteria for schizophrenia?
- Two or more of the following, each present for a significant part of 1 month (less if successfully treated), and at least one must be 1, 2 or 3: (1) delusions, (2) hallucinations, (3) disorganised speech (frequent derailment, incoherence), (4) grossly disorganised or catatonic behaviour, (5) negative symptoms (diminished emotional expression, avolition).
- Functional decline in work, relationships or self-care since onset.
- Continuous signs for at least 6 months, including at least 1 month of active-phase symptoms; the rest may be prodromal or residual (negative or attenuated symptoms).
- Schizoaffective, depressive and bipolar disorders with psychotic features are excluded, as are effects of substances or another medical condition.
- With a history of autism spectrum or communication disorder, prominent delusions or hallucinations for at least 1 month are additionally required.
| Disorder | Duration of psychotic symptoms |
|---|---|
| Brief psychotic disorder | 1 day to less than 1 month |
| Schizophreniform disorder | 1 month to less than 6 months |
| Schizophrenia | At least 6 months of continuous disturbance (≥ 1 month active phase) |
What are Schneider's first-rank symptoms?
Kurt Schneider proposed his first-rank symptoms (FRS) in a 1939 monograph as experiences especially suggestive of schizophrenia. Many came from the 'self-disturbances' described by the early Heidelberg school. They cluster into auditory hallucinations and delusional experiences of the self being controlled.
| Group | Symptom | What the patient reports |
|---|---|---|
| Auditory hallucinations | Audible thoughts / thought echo | Hears own thoughts spoken aloud |
| Auditory hallucinations | Voices arguing or discussing (third person) | Voices talk about the patient among themselves |
| Auditory hallucinations | Voices giving a running commentary | Voices comment on the patient's actions |
| Thought alienation | Thought insertion | Thoughts put into the mind by an outside agency |
| Thought alienation | Thought withdrawal | Thoughts taken out of the mind |
| Thought alienation | Thought broadcasting | Thoughts are known to or heard by others |
| Passivity (made) experiences | Made feelings, made impulses, made actions | Emotions, drives or movements controlled by an outside force |
| Passivity (made) experiences | Somatic passivity | Bodily sensations imposed from outside |
| Delusional perception | Delusional perception | A normal perception suddenly given a private, delusional meaning |
FRS shaped ICD-10, whose first symptom group is essentially Schneider's list (thought echo, insertion, withdrawal, broadcasting; delusions of control or passivity; delusional perception; running-commentary or discussing voices). ICD-11 deliberately moved away from this emphasis on first-rank symptoms, and FRS are not specific — they also occur in bipolar disorder.
How do positive and negative symptoms differ?
| Feature | Positive symptoms | Negative symptoms |
|---|---|---|
| Meaning | Abnormal experiences added to normal function | Normal functions lost or reduced |
| Examples | Hallucinations, delusions, disorganised speech and behaviour, catatonia | Diminished emotional expression (flat, blunted affect), avolition, poverty of speech, social withdrawal |
| Dopamine pathway | Excess dopamine activity in the mesolimbic pathway (VTA → limbic areas) | Reduced dopamine in the mesocortical pathway (VTA → cortex), also linked to cognitive deficits |
| Response to antipsychotics | Good | Little evidence of substantial benefit unless secondary to positive symptoms |
| Clinical note | Usually what brings the patient to care | More pronounced in men; cognitive deficits predict poorer outcome |
Four dopamine pathways are tested together: mesolimbic (positive symptoms), mesocortical (negative and cognitive symptoms), nigrostriatal (extrapyramidal side effects when blocked) and tuberoinfundibular (hyperprolactinaemia when blocked). Drug details are on the antipsychotics page.
Does ICD-11 still use paranoid, hebephrenic and catatonic subtypes?
No. ICD-10 subdivided schizophrenia by the dominant presentation; DSM-5-TR does not use subtypes; and ICD-11 (code 6A20) removed them, replacing them with a hybrid categorical-dimensional approach.
| ICD-10 subtypes (no longer used in ICD-11) | ICD-11 replacement |
|---|---|
| Paranoid | Course specifiers in the main code: first episode, multiple episodes, continuous; plus remission status |
| Hebephrenic (disorganised) | Symptom specifiers 6A25: positive, negative, depressive, manic, psychomotor, cognitive symptoms — each rated for severity |
| Catatonic | Catatonia is now a separate, cross-diagnostic disorder, not a schizophrenia subtype |
| Undifferentiated, residual, simple, post-schizophrenic depression | Captured by course and symptom specifiers |
ICD-11 core rule: at least two symptoms, at least one from the core group — delusions, hallucinations, thought disorder, or disturbances of self-experience (such as passivity and thought insertion) — present most of the time for at least 1 month, after excluding other causes.
Which factors predict good or poor prognosis in schizophrenia?
| Good prognosis | Poor prognosis |
|---|---|
| Acute onset | Insidious onset |
| Onset in adulthood | Childhood or adolescent onset |
| Good premorbid adjustment | Poor premorbid adjustment |
| Female sex (later onset, better premorbid functioning) | Male sex (earlier onset, poorer premorbid functioning, more negative symptoms) |
| No substance use | Substance use |
| Intact cognition | Cognitive impairment |
- Suicide is the most common cause of premature death; lifetime risk of death by suicide is 5% to 10%, and two-thirds report suicidal ideation at some point.
- Complete recovery occurs in only about 13.5% despite treatment.
- Life expectancy is about 15 years shorter than in the general population.
What causes schizophrenia and what must be ruled out?
Schizophrenia is a neurodevelopmental disorder in which genetic risk meets environmental triggers. The concordance in monozygotic twins is about 60% — high, but far from 100%, which shows how much the environment matters. Risk factors include obstetric complications, season of birth, severe maternal malnutrition, maternal influenza in pregnancy, family history, childhood trauma, social isolation, minority ethnicity, urban upbringing and migrant status.
Cannabis is the classic exam risk factor: THC can induce temporary psychosis, and in one study heavy users had 6 times the risk of a schizophrenia diagnosis. The risk appears dose-dependent and greater with early use and more potent strains.
| Condition | How it differs from schizophrenia |
|---|---|
| Schizoaffective disorder | Depressive or manic episodes run concurrently with active schizophrenia symptoms and are present for most of the illness |
| Mood disorder with psychotic features | Hallucinations/delusions occur only during depressive or manic episodes |
| Delusional disorder | Delusions without other characteristic symptoms such as prominent hallucinations or disorganised speech |
| Brief psychotic / schizophreniform disorder | Same symptoms but shorter duration (< 1 month / < 6 months) |
| Substance- or medication-induced psychosis | Symptoms explained by intoxication or withdrawal (e.g. cannabis, stimulants) |
Clinical picture on examination: affect may be flat, blunted or inappropriate; thought processes may show loose associations, illogical connections or thought blocking (suddenly stopping mid-sentence); motor signs of catatonia include stupor, mutism, odd gestures and posturing.
How is schizophrenia treated, and what is treatment-resistant schizophrenia?
Antipsychotics are the mainstay, combined with psychosocial interventions. No clear overall winner exists between first- and second-generation drugs; choice depends on side-effect profile. Clinical response lags behind peak D2 blockade by 2 to 4 weeks, so an adequate trial needs time and adherence.
Treatment-resistant schizophrenia — about one-third of patients — means persistent symptoms despite 2 or more adequate trials of antipsychotics at adequate doses and durations with documented adherence. Clozapine is the recommended option (about 40% respond) and is also preferred for persistent suicide or aggression risk. Because of agranulocytosis risk, the absolute neutrophil count is checked before starting, weekly for 6 months, every 2 weeks for the next 6 months, then monthly.