Classification of Schizophrenia

Schizophrenia is a severe mental disorder which occurs in around 1% of the population. It is more commonly found in men, more common in urban environments, and more common in working-class populations. Schizophrenia is classified (the grouping of symptoms into categories) according to symptoms listed in diagnostic manuals- the two main ones used are the ICD-10 (International Classification of Disease, edition 10) and the DSM-5 (Diagnostic and Statistical manual of Mental Disorders, edition 5). According to the DSM, one ‘positive symptom’ needs to be present. According to the ICD, two ‘negative symptoms’ are sufficient. Therefore, there are slight differences with how it is classified.

Positive symptoms: Refer to an excess of usual functioning; an ‘added’ behaviour or experience. For example, hallucinations are additional sensory experiences such as hearing voices, seeing things that aren’t there, or seeing images in a distorted way. Delusions are irrational beliefs, for example delusions of persecution are thoughts that the sufferer is being watched, monitored or controlled by outside forces. Delusions of grandeur involve the belief that the sufferer is an important historical figure. Some delusions can lead to aggressive acts, but it is far more common for sufferers to be victims of violence.

Negative symptoms: Refer to a loss of usual functioning. For example, avolition is the reduction of goal-directed activity, manifested as a lack of motivation and drive, making it difficult to go to work, maintain personal hygiene, or get out of bed. Speech poverty (‘alogia’) refers to changes in speech patterns, usually a reduction in the amount and quality of speech. Speech disorganisation involves incoherence and suddenly changing topic mid-sentence (disorganisation is classified in the DSM-5 as a positive symptom).

Schizophrenia, figure 1

Reliability & Validity

Reliability: This refers to consistency of diagnosis. Inter-rater reliability is the extent to which different assessors will arrive at the same conclusion when diagnosing the same patient. If schizophrenia is diagnosed inconsistently, this could be problematic, as it may be over or under-diagnosed by psychiatrists, meaning patients will be incorrectly labelled as ‘schizophrenic’, or not diagnosed, meaning they won’t receive the treatment they need.

Validity: The extent to which the classification of ‘schizophrenia’ is a true reflection of the illness the patient is suffering from (does it measure what it intends to measure?). Criterion validity is the extent to which using different classification systems produces the same diagnosis in the same patient. If there are differences here, then it suggests there is a lack of agreement over what schizophrenia actually is. This issue is also made problematic by:

  • Co-morbidity: The presence of two different disorders at the same time. If this is common, it may be that the two disorders are actually one disorder, and perhaps should be seen as one condition (for example, schizophrenia and depression).
  • Symptom overlap: When two or more disorder share some of the symptoms needed for classification. Schizophrenia and bipolar disorder share many symptoms (such as delusions and avolition), meaning that the same patient could receive two different diagnoses. As with co-morbidity, if disorders share many symptoms it may be more helpful to see them as one disorder.


  • Cheniaux et al (2009) found that inter-rater reliability amongst two psychiatrists was low. One diagnosed 26 out of 100 patients with schizophrenia using the DSM, and 44 out of 100 using the ICD. The other diagnosed 13 using the DSM and 24 using the ICD. This supports that the classification and diagnosis of the disorder is lacking in reliability and validity.
  • Buckley et al (2009) found that 50% of schizophrenia patients also had a diagnosis of depression, 29% had a post-traumatic stress diagnosis, and 23% had an OCD diagnosis. This supports that there are problems with validity, namely the issue of co-morbidity.
  • There is gender and cultural bias present in the diagnosis of schizophrenia. Men are far more likely to be diagnosed, potentially because women are able to cope better with the symptoms, and people of African origin are also more likely to be diagnosed. Perhaps this is due to the cultural significance of ‘hearing voices’, which may be seen by white Western psychiatrists as unusual or bizarre. These factors support that the classification of schizophrenia lacks validity and reliability.
Discuss issues of reliability and/or validity in the classification and diagnosis of schizophrenia. (16 marks - 6 outline - around 3 paragraphs; 10 evaluate - around 3-4 evaluation points)
Your answer should include: Reliability / Consistency / Validity / Co-morbidity / Symptom / Overlap / Cheniaux / Buckley / Cultural