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Critically Consider Biological Explanations Of Schizophrenia

The term ‘schizophrenia' covers a group of serious psychotic disorders characterised by a loss of contact with reality. It comes from two Greek words: schiz meaning ‘split' and phren meaning ‘mind'. DSM IV (1994) estimate that the occurrence rate of schizophrenia ranges from 0.2%-2.0% worldwide. There are two main explanations of schizophrenia: the biological explanations and the psychological explanations. In this essay I will critically consider the biological explanations. These include genetics, neurochemistry, brain structure and evolution.
Genetic factors of schizophrenia can be explained using studies on twins and studies on family history. With twin studies researchers want to establish the degree of concordance. This is the probability that if one twin has the disorder, the other twin will also have it. Monozygotic (MZ) twins share 100% of their genes and dizygotic (DZ) twins share about 50%. Gottesman (1991) summarised 40 twin studies and found that the concordance rate for MZ twins was 48% and the concordance rate for DZ twins was about 17%. Concordance rates were also studied by Cardano et al. (1999) using the Maudsley twin register. They found concordance rates to be 40% for MZ twins and 17% for DZ twins.
Although this is strong evidence for genetic factors in schizophrenia, concordance rates are not 100% and therefore there must be some environmental input. Loehlin and Nichols (1976) argued that the reason for the higher concordance rates in MZ rather than DZ twins was due to MZ twins being treated more similarly so producing a greater environmental similarity.
However, there are two arguments against this view. MZ twins may produce more similar treatment from their parents than do DZ twins (Lytton, 1977). This therefore suggests that the higher genetic similarity of MZ twins may be the cause, rather than the effect, of their more similar parental treatment. Also the schizophrenia concordance rates for MZ twins who are brought...