ETIOLOGY OF SCHIZOPHRENIA - A REVIEW OF THEORIES AND THEIR CLINICAL AND THERAPEUTIC IMPLICATIONS

For most of this century the causes of schizophrenia have been largely unknown, However, the application of new techniques in genetics, neur oimaging, psychopharmacology and epidemiology are beginning to disclos e the aetiology of the disorder, It is hoped that elucidation of the c auses of schizophrenia will lead to new and more effective treatments. Family and twin studies indicate that genetic factors are important, although single major genes for susceptibility have not yet been ident ified. If the genes are determined, gene therapy may become a viable o ption for the treatment of schizophrenia. Environmental factors are al so important and may explain the seasonal variation in births of indiv iduals with schizophrenia and regional variations in the incidence of the disorder. The contributions of obstetric complications and materna l influenza virus infection to schizophrenia are currently being evalu ated. There are observed differences in the presentation of schizophre nia between males and females, and these need to be accounted for by a etiological theories. Several observations support the theory that sch izophrenia results from processes occurring during neurodevelopment. T hese processes may be responsible for structural and functional abnorm alities that have been detected in the brains of patients with schizop hrenia. Abnormalities in the temporal lobe have been related to halluc inations, delusions and thought disorder, while abnormalities in the f rontal lobe have been associated with negative symptoms. Observed diff erences between schizophrenic patients and healthy individuals in the size of the corpus callosum and subcortical structures may also have n eurodevelopmental origins. At the neurochemical level, dysfunction of central dopamine systems may mediate symptoms of schizophrenia. Tradit ional antipsychotics are antagonists of dopamine D-2-receptors, but so me of the new atypical antipsychotics appear to have a different actio n and drugs that interact with newly discovered receptor subtypes are under investigation. Schizophrenia has significant psychosocial conseq uences for the patient, and psychosocial factors such as adverse life events and high expressed emotion in the family have been observed to increase the likelihood of relapses of the disorder.