Outline and evaluate one or more biological explanations for schizophrenia

Schizophrenia can be explained genetically if seen as a inherited condition, for example if both parents have had the disease than there is a 46% chance of the child having it. However monozygotic twins share the same genetics and therefore would lead us to think that if one twin had it than there'd be a 100% chance of the other twin having schizophrenia but this not the case. There is only a 48% chance of the other twin being diagnosed which leads us two think that there may be other factors that effect a persons chances of developing schizophrenia. The twin studies and adoption studies try to discover these. The twin studies assumed that although both MZ and DZ twins share the same environment with their twin, MZ twins should show a higher concordance rate as they are more genetically similar. DZ twins share around 50% of there genes to their twin. Gottesman (1991) found this to be true, but a criticism for the twin studies is its low population validity due to the fact that monozygotic twins are quite rare and of these only 1% is expected to have schizophrenia. Therefore sample sizes are usually quite small. Another point is that different ways of calculating the concordance rates occurred, dependant on the method that was used. This means that it isn't possible to compare some studies. Furthermore the diagnostic criteria was at fault, as twin studies do not all use the same diagnostic criteria so comparisons cannot always be made. Different definitions produce different concordance rates. There was also diagnoses problems with establishing whether the twin was mono-zygotic or dis-zygotic. With advanced techniques in genetic research it is now easier to diagnose accurately, however in many of the twin studies this was not the case. A further criticism is reductionist, in the twin studies the experimenters assume that the environment of the twins is the same, however it is pointed out by Joseph (2004) that MZ twins will be treated more similarly and experience more similar environment than DZ twins. Therefore concordance rates may represent true findings of a biological explanation of schizophrenia.

The Adoption study looks at children that have had a schizophrenic mother but have been adopted to see if schizophrenia can be pinned down to the environmental or genetic factors. Tienari (1991) carried out a Finnish Adoption study, with 155 adopted children with schizophrenic mothers compared to a match group with no schizophrenia family history. The findings showed that 10% from the group that mothers had schizophrenia developed schizophrenia compared to 1% with no family history of schizophrenia. This would suggest genetics is the main component for developing schizophrenia but Wahlberg et al re-examined some data and found that children who were adopted into poor communication families were at a higher risk of developing schizophrenia. Suggesting that family factors may have a bigger effect then genetics. Another problem in these longitudinal studies is that over time diagnostic criteria may changed. This means the mother and child may both have the same symptoms but because diagnosed at different times they're diagnosed differently. Also in some cases (Denmark, America) the adoptive parents would have been given genetic background info on the child, seeing a child with a schizophrenic mother may make the adoptive parents change which child they choose to adopt.

Another explanation for schizophrenia is the dopamine hypothesis, this