Definition and classification

Schizophrenia is typically associated with disorder of thinking, perception, and with inappropriate or blunted affect. As the disorder progresses, it often ultimately leads to a disintegration of personality. Intellectual capacity and conciousness are usually initially normal, however, intellectual impairments are common over the course of the illness (Remschmidt, 2001).

Little is known about the causes of schizophrenia. The classification systems ICD-10 and DSM-IV (WHO, 1992; APA, 1994) base the diagnosis on the symptoms of the disorder and define specific time criteria for the onset and course of schizophrenia.

In ICD-10, a diagnosis of schizophrenia requires the presence of at least one of the symptoms 1–4 listed below (two or more symptoms are required if they are not very clear), or at least two of the symptoms 5–8 (WHO, 1992):

1. thought echo, thought insertion or withdrawal, and thought broadcasting;

2. delusions of control, influence, or passivity, clearly referred to body or limb movements or specific thoughts, actions, or sensations; delusional perceptions;

3. 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;

4. persistent delusions of other kinds that are culturally inappropriate and completely impossible, such as religious or political identity, or superhuman powers and abilities, e.g. being able to control the weather, or being in communication with aliens from another world;

5. persistent hallucinations in any modality, when accompanied either by fleeting or half-formed delusions without clear affective content, or by persistent over-valued ideas, or when occurring every day for weeks or months on end;

6. […]