Schizophrenia

The most widely used criteria in the US are those from the Diagnostic and Statistical Manual of Mental Disorders. Some specialists will instead use the World Health Organization (WHO) International Classification of Diseases criteria.

Diagnostic and statistical manual of mental disorders, fifth edition (DSM-5-TR)[1]American Psychiatric Association. Diagnostic and statistical manual of mental disorders, 5th ed., text revision (DSM-5-TR). Washington, DC: American Psychiatric Publishing; 2022. https://www.psychiatry.org/psychiatrists/practice/dsm

Schizophrenia can be diagnosed if the following conditions are met:

1. Two (or more) of the following symptoms, each present for a significant portion of time during a 1-month period (or less if successfully treated). At least one of these symptoms must be items 1, 2, or 3 below:

   1. Delusions

   2. Hallucinations

   3. Disorganized speech (e.g., frequent derailment or incoherence)

   4. Grossly disorganized or catatonic behavior

   5. Negative symptoms (i.e., diminished emotional expression or avolition)

2. For a significant portion of the time since the onset of the disturbance, level of functioning in one or more major areas, such as work, interpersonal relations, or self-care, is markedly below the level achieved prior to the onset (or, when the onset is in childhood or adolescence, there is failure to achieve expected level of interpersonal, academic, or occupational functioning).

3. Continuous signs of the disturbance persist for at least 6 months. This 6-month period must include at least 1 month of symptoms (or less if successfully treated) that meet criterion A (i.e., active-phase symptoms) and may include periods of prodromal or residual symptoms. During these prodromal or residual periods, the signs of the disturbance may be manifested by only negative symptoms or by two or more symptoms listed in criterion A present in an attenuated form (e.g., odd beliefs, unusual perceptual experiences).

4. Schizoaffective disorder and depressive or bipolar disorder with psychotic features have been ruled out because either: 1) no major depressive or manic episodes have occurred concurrently with the active-phase symptoms, or 2) if mood episodes have occurred during active-phase symptoms, they have been present for a minority of the total duration of the active and residual periods of the illness.

5. The disturbance is not attributable to the physiologic effects of a substance (e.g., a drug of abuse, a medication) or another medical condition.

6. If there is a history of autism spectrum disorder or a communication disorder of childhood onset, the additional diagnosis of schizophrenia is made only if prominent delusions or hallucinations, in addition to the other required symptoms of schizophrenia, are also present for at least 1 month (or less if successfully treated).

International Classification of Disease (ICD-11)[78]World Health Organization. International statistical classification of diseases and related health problems, 11th revision (ICD-11). Chapter 6: mental, behavioural or neurodevelopmental disorders. 2022 [internet publication]. https://icd.who.int/en

The WHO International Classification of Diseases (ICD-11) criteria for schizophrenia require at least two of the following symptoms (by the individual’s report or through observation by the clinician or other informants) most of the time for a period of 1 month or more. At least one of the qualifying symptoms should be from items A to D below:

1. Persistent delusions (e.g., grandiose delusions, delusions of reference, persecutory delusions).

2. Persistent hallucinations (most commonly auditory, although they may be in any sensory modality).

3. Disorganized thinking (formal thought disorder) (e.g., tangentiality and loose associations, irrelevant speech, neologisms). When severe, the person’s speech may be so incoherent as to be incomprehensible ("word salad").

4. Experiences of influence, passivity, or control (i.e., the experience that one’s feelings, impulses, actions, or thoughts are not generated by oneself, are being placed in one’s mind or withdrawn from one’s mind by others, or that one’s thoughts are being broadcast to others).

5. Negative symptoms such as affective flattening, alogia or paucity of speech, avolition, asociality, and anhedonia.

6. Grossly disorganized behavior that impedes goal-directed activity (e.g., behavior that appears bizarre or purposeless, unpredictable or inappropriate emotional responses that interferes with the ability to organize behavior.)

7. Psychomotor disturbances such as catatonic restlessness or agitation, posturing, waxy flexibility, negativism, mutism, or stupor. Note: if the full syndrome of catatonia is present in the context of schizophrenia, the diagnosis of catatonia associated with another mental disorder should also be assigned.