[Psychosis: from diagnosis to syndrome].

Psychotic disorders such as schizophrenia are associated with severe psychological suffering for the patient and high healthcare costs. The initial symptoms typically emerge in adolescence and early adulthood. The incidence varies considerably from place to place and among different groups of immigrants. The symptoms, clinical course, and treatment response differs per individual. Genetic vulnerability for psychotic disorders is shared in part with bipolar disorder, and recent molecular genetic findings also indicate an overlap with developmental disorders such as autism. The diagnosis of schizophrenia is associated with demonstrable alterations in brain structure and changes in dopamine neurotransmission, the latter being directly related to hallucinations and delusions. Antipsychotics, which block the dopamine system, are effective for delusions and hallucinations but less so for disabling cognitive and motivational impairments. A better understanding of the biological mechanisms and the psychosocial factors underlying psychotic disorders may contribute to new treatments.