Psychotic symptoms in ICD-11: delusions, hallucinations, disorganised thinking and diagnostic criteria

Hallucinations - diagnostic significance

Hallucinations are perceptual experiences that occur without a corresponding external stimulus. They may involve hearing voices or sounds, seeing figures or images, feeling touch or bodily sensations, smelling odours or tasting something that is not present. Auditory hallucinations are especially important in psychotic disorders, but the modality alone does not establish a diagnosis.

The diagnostic meaning of hallucinations depends on persistence, frequency, degree of conviction, impact on behaviour, associated distress and relation to other symptoms. A brief experience while falling asleep is very different from persistent voices commenting on a person's actions or commanding behaviour. ICD-11 therefore requires a full clinical assessment rather than a simple yes-or-no symptom count [1, 2].

Hallucination-like experiences can also appear in sleep deprivation, severe stress, bereavement, fever, delirium, neurocognitive disorders, neurological disease and after psychoactive substances. Their presence should prompt assessment of consciousness, attention, cognition, substance use, medications and somatic or neurological signs [10, 12, 13, 14].

Disorganised thinking and behaviour

Disorganised thinking is most often inferred from speech. A person may lose the thread, shift rapidly between loosely connected topics, answer beside the point, use markedly incoherent associations or become difficult to follow. Mild circumstantiality is not enough by itself; diagnostic importance increases when the disturbance is persistent, clinically marked and not better explained by language barriers, culture, intoxication, delirium or cognitive disorder.

Disorganised behaviour may include actions that are markedly inappropriate to the situation, poorly goal-directed, unpredictable or difficult to understand in context. In psychotic disorders it can coexist with delusions, hallucinations, negative symptoms or psychomotor disturbance. It is important to distinguish it from agitation caused by anxiety, mania, intoxication, withdrawal, delirium or an acute medical condition [1, 2].

Negative symptoms - easy to miss, important for functioning

Negative symptoms describe a reduction or loss of normal functions. They may include diminished emotional expression, reduced speech, reduced motivation, lowered social engagement and reduced capacity to experience pleasure. They are often less visible than delusions or hallucinations, yet they may be strongly associated with impaired social and occupational functioning [7, 8].

Clinical assessment has to separate primary negative symptoms from secondary causes. Similar-looking withdrawal or reduced activity may result from depression, anxiety, medication adverse effects, substance use, social deprivation, demoralisation or consequences of repeated hospitalisation. The overlap with depression is especially important: low mood, guilt, suicidal thoughts and pessimism point more strongly toward a depressive component, whereas alogia and blunted affect more often suggest negative symptoms [9].

ICD-11 group 6A2 - primary psychotic disorders

In ICD-11, the group of schizophrenia or other primary psychotic disorders includes several diagnostic categories. Their shared feature is that psychotic symptoms are not better explained by substances, medications, withdrawal, a medical or neurological condition, delirium or another mental disorder [1, 2].

6A20 Schizophrenia requires at least two criterion symptoms to be present for most of the time for at least 1 month. At least one must be persistent delusions, persistent hallucinations, disorganised thinking or experiences of influence, passivity or control.

6A21 Schizoaffective disorder is used when the diagnostic requirements for schizophrenia and a mood episode are met within the same episode of illness. 6A22 Schizotypal disorder involves a persistent pattern of unusual thinking, perception, beliefs, speech, affect and behaviour that does not reach the threshold for schizophrenia.

6A23 Acute and transient psychotic disorder has an abrupt onset, rapid development of full severity within no more than 2 weeks, a variable or fluctuating picture and duration not exceeding 3 months. 6A24 Delusional disorder requires a delusion or a set of related delusions, usually lasting at least 3 months, without persistent hallucinations, marked disorganisation or negative symptoms dominating the picture.

Schizophrenia in ICD-11 - key criteria

ICD-11 schizophrenia is not diagnosed on the basis of a single symptom. The clinical picture must include at least two criterion symptoms, present for most of the time for at least 1 month. At least one must be persistent delusions, persistent hallucinations, disorganised thinking or experiences of influence, passivity or control [1, 2].

Other symptoms include negative symptoms, grossly disorganised behaviour and psychomotor disturbances, including catatonic symptoms. A major difference from DSM-5-TR is duration: ICD-11 requires characteristic symptoms for at least 1 month, whereas DSM-5-TR requires a total disturbance duration of at least 6 months [4, 5].

Psychotic symptoms outside group 6A2

Psychotic symptoms may occur outside the group of schizophrenia or other primary psychotic disorders. This is crucial in ICD-11 diagnosis because the mere presence of delusions or hallucinations is not enough to diagnose schizophrenia or another primary psychotic disorder [1, 2].

In mood disorders, psychotic symptoms may appear during depressive, manic or mixed episodes. If psychotic symptoms occur only during a mood episode, the diagnosis should primarily reflect a mood disorder with psychotic symptoms rather than schizophrenia. In substance- or medication-induced disorders, timing is essential: the clinician assesses the relation between exposure, intoxication, withdrawal and symptom onset.

ICD-11 also includes 6E61 secondary psychotic syndrome, used when psychotic symptoms are a direct consequence of a condition classified outside the mental disorders chapter. Differential diagnosis is especially important in delirium, dementia, epilepsy, brain tumours, autoimmune disease, endocrine disorders and medication effects [10, 11].

Catatonia in ICD-11

ICD-11 treats catatonia as a psychomotor syndrome that can occur in different mental disorders, after substances or medications, and as a consequence of medical conditions. It may include stupor, mutism, negativism, posturing, waxy flexibility, catatonic excitement, stereotypies, mannerisms and other disturbances of psychomotor activity [1, 2].

ICD-11 distinguishes, among others, 6A40 catatonia associated with another mental disorder, 6A41 catatonia induced by substances or medications and 6E69 secondary catatonia syndrome. Catatonia requires urgent clinical assessment because some presentations may be associated with serious medical complications [11].

First episode psychosis, course and early intervention

ICD-11 allows the course of primary psychotic disorders to be described. In schizophrenia, clinicians can specify first episode, multiple episodes, continuous course, current symptomatic state, partial remission or full remission. The diagnosis therefore describes not only the name of the disorder but also the stage and current clinical state.

Clinically, first episode psychosis is especially important. Longer duration of untreated psychosis, commonly abbreviated as DUP, is associated with worse clinical and functional outcomes. A large meta-analysis of 369 studies estimated a mean DUP of 42.6 weeks and a median of 14 weeks [15].

This does not mean that DUP is the only prognostic factor. It means that prompt recognition of symptoms, risk assessment, exclusion of medical causes and referral to appropriate care are more useful than passively waiting for complete diagnostic certainty [16].

Differential diagnosis - practical order of assessment

Assessment of psychotic symptoms can be organised around several clinical questions. First, consider substances, medications and withdrawal: alcohol, cannabinoids, stimulants, sedatives, opioids, steroids, dopaminergic medication and other agents that can affect mental state. Second, consider delirium and medical causes, especially when there is disturbed consciousness, impaired attention, disorientation, fever, seizures, focal neurological signs, cognitive decline, sudden onset or an unusual age at first onset.

Third, assess mood. If delusions or hallucinations occur only during a depressive, manic or mixed episode, the diagnosis should reflect a mood disorder with psychotic symptoms. Fourth, assess duration and dynamics: abrupt onset and duration up to 3 months support acute and transient psychotic disorder; at least 1 month of characteristic symptoms may support schizophrenia; stable delusions lasting usually at least 3 months support delusional disorder.

Fifth, consider cultural context. Beliefs, practices or experiences consistent with cultural, religious or subcultural norms should not be automatically classified as psychotic. Collateral information and cultural consultation may be essential when the context is unfamiliar.

When to consider autoimmune or neurological causes?

Although many episodes of psychosis are primarily psychiatric, some psychotic symptoms may result from neurological or autoimmune disease, including autoimmune encephalitis. Warning signs include very abrupt onset, rapidly progressive memory impairment, confusion, seizures, dyskinesias, speech disturbance, autonomic symptoms, focal neurological signs, catatonia, an unusual reaction to antipsychotic medication or rapid progression despite treatment [10, 11].

In such cases, psychiatric assessment should be complemented by medical and neurological evaluation. Depending on the clinical picture, this may include neurological examination, laboratory tests, neuroimaging, EEG, cerebrospinal fluid testing or neuronal antibody testing. Not every person with psychosis needs a full autoimmune work-up, but red flags should lower the threshold for neurological consultation.

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