3. DSM‐IV criteria for schizophrenia.

A*	Characteristic symptoms: Two or more of the following, each present for a significant portion of time during a one‐month period: delusions hallucinations disorganised speech (e.g. frequent derailment or incoherence) grossly disorganised or catatonic behaviour negative symptoms (i.e. affective flattening, alogia, or avolition).
B	Social/occupational dysfunction: Since the onset of the disturbance, one or more major areas of functioning, such as work, interpersonal relations, or self‐care, are markedly below the level previously achieved.
C	Duration: Continuous signs of the disturbance persist for at least six months. This six‐month period must include at least one month of symptoms (or less if successfully treated) that meet Criterion A.
D	Exclusion of schizoaffective disorder and mood disorder with psychotic features.
E	Substance/general medical condition exclusion: the disturbance is not due to the direct physiological effects of a substance (e.g. a drug of abuse, a medication) or a general medical condition.
F	Relationship to a pervasive developmental disorder: If there is a history of autistic disorder or another pervasive development disorder, the diagnosis of schizophrenia is made only if prominent delusions or hallucinations are also present for at least a month (or less if successfully treated).
* Only one Criterion A symptom is required if delusions are bizarre or hallucinations consist of a voice keeping up a running commentary on the person's behaviour or thoughts, or two or more voices conversing with each other.

DSM: Diagnostic and Statistical Manual of Mental Disorder