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There has been much debate regarding the causes of schizophrenia and it is still a topic that receives much deliberation throughout the biological psychology realm. However, it is now generally agreed upon that schizophrenia develops over time via a complex interaction between an individual’s biological predisposition and the environment that the individual is continually exposed to. Thus, research suggests that children who are genetically predisposed to schizophrenia (i.e. the condition runs in their family history) and encounter stressful/emotional life experiences, are at an increased risk of developing schizophrenia. Twin studies have provided convincing evidence to suggest that genetics at least contribute to the development of schizophrenia, with Cardno & Gottesman (2000), for example, demonstrating that, if one identical twin (i.e. sharing identical genes) develops schizophrenia, the likelihood of the other twin also developing the condition is around 41-65% - even if the twins are brought up apart. In comparison, if one non-identical twin develops schizophrenia, the other one has a 0-28% of also developing the condition. Whilst there are, of course, criticisms of twin studies, they have been crucial in stressing the importance of genetics in the etiology of schizophrenia. Nevertheless, environmental factors (e.g. adverse child rearing; drug abuse), and their interaction with genetics, are also thought to be vitally important in the development of the condition.
ReferencesCardno, A. G. and Gottesman, I. l., (2000). Twin studies of schizophrenia: from bow-and-arrow concordances to star wars Mx and functional genomics. American Journal of Medical Genetics, 97(1), 12-7.