The biological theories, which may explain Schizophrenia - Essay Example

These concern genetics, neurochemistry, brain structure and evolution. Biological 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 likelihood that if one twin has the disorder, the other twin will also have it. Gottesman (2000) 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. (2001) using the Maudsley twin registers. They found concordance rates to be 40% for MZ twins and 17% for DZ twins. Although this is strong evidence for biological factors in Schizophrenia, concordance rates are not 100% and therefore there must be some environmental input. Loehlin and Nichols (2002) 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, 2000). This therefore suggests that the higher biological similarity of MZ twins may be the cause, rather than the effect, of their more similar parental treatment. In addition, the Schizophrenia concordance rates for MZ twins who are brought up apart are similar to those of MZ twins who are brought up together (Sheilds, 2003). So presumably the high concordance rates of MZ's brought up apart is not due to environmental similarity.

However, it has been suggested that some of the twins who had been brought up separately in Sheilds study had not always spent their whole childhood apart and some were raised by relatives and even went to the same school (e.g. Kamin, 2001).Family studies also aid to explain how biological factors influence Schizophrenia. Gottesman (2000) found that if you have a sibling with the disorder you have an 8% chance of being Schizophrenic, if you have one parent with the disorder you have a 16% chance of being Schizophrenic and if you have two parents with the disorder you have a 46% chance of being Schizophrenic.

These concordance rates should all be compared to the 1% chance that a person randomly selected from the population would be Schizophrenic.Gottesman and Bertelsen (2001) also reported some convincing findings on the importance of genetics. The found that participants had a 17% chance of being Schizophrenic if they had a parent who was an identical twin and who had Schizophrenia. This could be due to heredity or environment. They also found that participants had a 17% chance of being Schizophrenic if they had a parent who was an identical twin and did not have Schizophrenia, but whose identical twin did.

This therefore shows that the most important factor is genetics. The evidence reported by Gottesman is criticised because although it indicates that Schizophrenia runs in families and that concordance rates are much higher between relatives who have higher biological similarity, it does not account for the fact that family members who are more biologically similar are likely to spend more time together. This means that environmental factors are also indicated in this