Schizophrenia

Schizophrenia is most commonly characterized by both 'positive symptoms' (those additional to normal experience and behaviour) and 'negative symptoms' (the lack or decline in normal experience or behaviour). Positive symptoms are grouped under the umbrella term psychosis and typically include delusions, hallucinations, and thought disorder. Negative symptoms may include inappropriate or lack of emotion, poverty of speech, and lack of motivation. Some models of schizophrenia include thought disorder and planning problems in a third grouping, the 'disorganization syndrome'. Additionally, neurocognitive deficits may be present. These take the form of reduction or impairment in basic psychological functions such as memory, attention, problem solving, executive function and social cognition. The onset is typically in late adolescence and early adulthood, with males tending to show symptoms earlier than females.

Below is an abbreviated version of the diagnostic criteria from the DSM-IV-TR.To be diagnosed as having schizophrenia, a person must display:

* A) Characteristic symptoms: Two or more of the following, each present for a significant portion of time during a one-month period (or less, if successfully treated)
o delusions
o hallucinations
o disorganized speech (e.g., frequent derailment or incoherence). See thought disorder.
o grossly disorganized or catatonic behavior
o negative symptoms, i.e., affective flattening (lack or decline in emotional response), alogia (lack or decline in speech), or avolition (lack or decline in motivation).

Note: Only one Criterion A symptom is required if delusions are bizarre or hallucinations consist of hearing voices.

* B) Social/occupational dysfunction: For a significant portion of the time 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 achieved prior to the onset.

* 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.

Historically, schizophrenia in the West was classified into simple, catatonic, hebephrenic, and paranoid. The DSM now contains five sub-classifications of schizophrenia. These are

* catatonic type (where marked absences or peculiarities of movement are present),
* disorganized type (where thought disorder and flat or inappropriate affect are present together),
* paranoid type (where delusions and hallucinations are present but thought disorder, disorganized behaviour, and affective flattening is absent),
* residual type (where positive symptoms are present at a low intensity only) and
* undifferentiated type (psychotic symptoms are present but the criteria for paranoid, disorganized, or catatonic types has not been met).

Symptoms may also be described as 'positive symptoms' (those additional to normal experience and behaviour) and negative symptoms (the lack or decline in normal experience or behaviour). 'Positive symptoms' describe psychosis and typically include delusions, hallucinations and thought disorder. 'Negative symptoms' describe inappropriate or nonpresent emotion, poverty of speech, and lack of motivation. In three-factor models of schizophrenia, a third symptom grouping, the so called 'disorganisation syndrome' is also given. This considers thought disorder and related disorganized behaviour to be in a separate symptom cluster from delusions and hallucinations.

It is worth noting that many of the positive or psychotic symptoms may occur in a variety of disorders and not only in schizophrenia.