How schizophrenia is diagnosed

Schizophrenia is diagnosed on the basis of an interview conducted by the consultant psychiatrist with the affected person. Specific diagnostic tools, in the form of a series of structured questions, will be used during the interview which are about 90% accurate in diagnosing schizophrenia.

Other relevant information about the patient will also be taken into account, often from relatives or people who are very close to the patient.1

If the patient is in a state of crisis, the doctor may consider having them sectioned under the Mental Health Act. This will also involve the patient’s GP and a qualified social worker.1

Methods of diagnosis

In the UK and the rest of the Europe, diagnosis of schizophrenia is based on the International Classification of Diseases (ICD), 10th revision.2 In the USA, the main diagnostic method is based on the Diagnostic and Statistical Manual (known as DSM IV).

Disorders of brain function are rarely clear-cut due to their complexity, so a working diagnosis may be made initially which may later be changed as the doctor gets to know the patient.

Schizophrenia and schizo-affective disorder

As well as schizophrenia, the other psychotic illness is bipolar disorder, which is characterized by mood disturbances, such as depression, and periods of mania. If the patient shows symptoms of schizophrenia with mood or manic disturbances, the psychiatrist may give a working diagnosis of schizo-affective disorder, which fall in between schizophrenia and bipolar disorder.

As more information is gathered on the patient and their on-going symptoms, the diagnosis may be changed to schizophrenia or bipolar disorder as appropriate.1

Positive and negative symptoms

Symptoms of schizophrenia are usually divided into two categories: positive and negative.

Diagnostic criteria for schizophrenia

There are four criteria that must be fulfilled in order to make a diagnosis of schizophrenia:

  • The person must have at least one clear symptom that is characteristic of schizophrenia such as hallucinations.

  • The symptom must have been present for at least 1 month, and the disturbances to their life must have been present for at least 6 months.

  • The symptoms must be having a negative impact on the person’s social functioning or their occupation, such as work or studies.

  • Other factors which may cause the symptom must have been ruled out, such as use of recreational drugs.1

Subtypes of schizophrenia

There are many subtypes of schizophrenia, but there are seven main ones which occur most frequently3:

  • Paranoid schizophrenia

  • Hebephrenic schizophrenia

  • Catatonic schizophrenia

  • Undifferentiated schizophrenia

  • Postschizophrenic depression

  • Residual schizophrenia

  • Simple schizophrenia

With the exception of simple schizophrenia which has its own criteria, all these subtypes must meet the general criteria for the diagnosis of schizophrenia, plus some subtype-specific criteria in the ICD-10. These criteria will be listed in the following section.

ICD-10 Diagnostic Criteria for Schizophrenia

ICD-10 general criteria for the diagnosis of schizophrenia

The general criteria listed in the ICD-10 for the diagnosis of schizophrenia is listed below.3,4

Either at least one of the syndromes, symptoms, and signs listed under (1) below, or at least two of the symptoms and signs listed under (2) should be present for most of the time during an episode of psychotic illness lasting for at least 1 month (or at some time during most of the days).

1. At least one of the following must be present:

  • Thought echo, thought insertion or withdrawal, or thought broadcasting

  • Delusions of control, influence, or passivity, clearly referred to body or limb movements or specific thoughts, actions, or sensations; delusional perception

  • Hallucinatory voices giving a running commentary on the patient’s behaviour, or discussing the patient among themselves, or other types of hallucinatory voices coming from some part of the body

  • Persistent delusions of other kinds that are culturally inappropriate and completely impossible (e.g., being able to control the weather, or being in communication with aliens from another world)

2. Or at least two of the following:

  • Persistent hallucinations in any modality, when occurring every day for at least 1 month, when accompanied by delusions (which may be fleeting or half-formed) without clear affective content, or when accompanied by persistent overvalued ideas

  • Neologisms, breaks, or interpolations in the train of thought, resulting in incoherence or irrelevant speech

  • Catatonic behaviour, such as excitement, posturing or waxy flexibility, negativism, mutism, and stupor

  • Negative symptoms, such as marked apathy, paucity of speech, and blunting or incongruity of emotional responses (it must be clear that these are not due to depression or to neuroleptic medication)

The most common exclusion clauses are:

  • If the patient also meets criteria for manic episode or depressive episode, the criteria listed under section (1) and (2) above must have been met before the disturbance of mood developed.

  • The disorder is not attributable to organic brain disease or to alcohol- or drug-related intoxication, dependence, or withdrawal.

ICD-10 criteria for the diagnosis of specific schizophrenia subtypes

Specific schizophrenia subtypes have their own criteria for diagnosis in the ICD-10, in addition to the general criteria above.4


    1. 1.The general criteria for schizophrenia must be met.

    2. 2. Delusions or hallucinations must be prominent (such as delusions of persecution, reference, exalted birth, special mission, bodily change, or jealousy; threatening or commanding voices, hallucinations of smell or taste, sexual or other bodily sensations).

    3. 3.Flattening or incongruity of affect, catatonic symptoms, or incoherent speech must not dominate the clinical picture, although they may be present to a mild degree.


    1. 1.The general criteria for schizophrenia must be met.

    2. 2.Either of the following must be present:

      1. Definite and sustained flattening or shallowness of affect.

      2. Definite and sustained incongruity or inappropriateness of affect.

    3. 3. Either of the following must be present:

      1. Behaviour that is aimless and disjointed rather than goal-directed.

      2. Definite thought disorder, manifesting as speech that is disjointed, rambling, or incoherent.

    4. 4. Hallucinations or delusions must not dominate the clinical picture, although they may be present to a mild degree.


    1. 1.The general criteria for schizophrenia must eventually be met, although this may not be possible initially if the patient is uncommunicative.

    2. 2.For a period of at least 2 weeks one or more of the following catatonic behaviours must be prominent:

      1. Stupor (marked decrease in reactivity to the environment and reduction of spontaneous movements and activity) or mutism.

      2. Excitement (apparently purposeless motor activity, not influenced by external stimuli).

      3. Posturing (voluntary assumption and maintenance of inappropriate or bizarre postures).

      4. Negativism (an apparently motiveless resistance to all instructions or attempts to be moved, or movement in the opposite direction).

      5. Rigidity (maintenance of a rigid posture against efforts to be moved).

      6. Waxy flexibility (maintenance of limbs and body in externally imposed positions).

      7. Command automatism (automatic compliance with instruction).


    1. 1.The general criteria for schizophrenia must be met.

    2. 2. Either of the following must apply:

      1. Insufficient symptoms to meet the criteria for any of the subtypes.

      2. So many symptoms that the criteria for more than one of the subtypes listed above are met.


    1. 1.The general criteria for schizophrenia must have been met within the past 12 months, but are not met at the present time.

    2. 2. One of the conditions for general schizophrenia in criterion 2 (a-d) must still be present.

    3. 3. The depressive symptoms must be sufficiently prolonged, severe, and extensive to meet criteria for at least a mild depressive episode.


    1. 1.The general criteria for schizophrenia must have been met at some time in the past but are not met at the present time.

    2. 2.At least four of the following negative symptoms have been present throughout the previous 12 months:

      1. Psychomotor slowing or underactivity.

      2. Definite blunting of affect.

      3. Passivity and lack of initiative.

      4. Poverty of either the quantity or the content of speech.

      5. Poor nonverbal communication by facial expression, eye contact, voice modulation, or posture.

      6. Poor social performance or self-care.


    1. 1. There is slow but progressive development, over a period of at least 1 year, of all three of the following:

      1. A significant and consistent change in the overall quality of some aspects of personal behaviour, manifest as loss of drive and interests, aimlessness, idleness, a self-absorbed attitude, and social withdrawal.

      2. A gradual appearance and deepening of negative symptoms such as marked apathy, paucity of speech, underactivity, blunting of affect, passivity and lack of initiative, and poor nonverbal communication (by facial expression, eye contact, voice modulation, and posture).

      3. A marked decline in social, scholastic, or occupational performance.

    2. 2. At no time are there any of the criteria for general schizophrenia, nor are there hallucinations or well-formed delusions of any kind; i.e., the individual must never have met the criteria for any other type of schizophrenia or for any other psychotic disorder.

    3. 3. There is no evidence of dementia or any other organic mental disorder.


    1. 1. e.g. cenesthopathic schizophrenia – a disorder in which patients complain about or have delusions of a general sense of bodily existence.

    2. 2. Unspecified schizophrenia


  1. Living with schizophrenia UK. Available at: (accessed March 2018).
  2. International Statistical Classification of Diseases and Related Health Problems, 10th Revision (ICD-10)-WHO Version; 2016. Available at: (accessed March 2018).
  3. Kraeplin Psychiatry. WordPress, 2010. Available at: (accessed March 2018).
  4. World Health Organization. The ICD-10 Classification of Mental and Behavioural Disorders: Diagnostic Criteria for Research. Copyright, World Health Organization, Geneva, 1993.

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