Schizophrenia is a disease with a worldwide distribution, affecting about 2-9 individuals per 1000 with little difference between countries (at least in western countries). Causes of its development are largely unknown, but probably consist of a variable interaction between environmental factors (family, education, problems of life, etc.) and an individual's inherited vulnerability.
From a clinical point of view schizophrenia can be divided into an acute and a chronic form; acute schizophrenia is characterized by symptoms like delusional ideas (the fact of thinking things that are not true or correct) and hallucinations (the fact of seeing, hearing, feeling things that don't exist). In the acute form of schizophrenia, contact with everyday reality can be lost and/or disturbed and dangerous behaviour against self or others can develop.
Chronic schizophrenia is a possible evolution of the acute state, and is characterized by lack of interest and motivation in life, social withdrawal, suspiciousness and affective flattening. Chronic impairment of work, social, or mental functioning may result in severe life-long disablement.
The diagnosis of schizophrenia is usually made by a psychiatrist by observation of the clinical features of the disorder.