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Outline and evaluate one or more biological explanation of schizophrenia.
One biological explanation of schizophrenia is genetics. Family, twin and adoption studies suggest
that genetics play a role in the development of schizophrenia. Children of two schizophrenic
biological parents have a 46% chance of developing schizophrenia themselves. Gottesman found
that in MZ twins there is a 48% concordance rate, whereas in DZ twins there is a 17% concordance
rate. This would suggest that genetics do play a significant role in the onset of schizophrenia,
however it is not 100% caused by it. Kety also supports this from their study in which they found
higher concordance rates for adoptive children and their biological parents when their environments
were matched. There are limited environmental factors that could cause the child or parents to be
more likely to develop schizophrenia which indicates that genetics play an important role in
developing schizophrenia. Sherrington found that a gene on chromosome 5 could be linked to
schizophrenia. This, however, was a small study of extended families and has failed to be replicated
so it has questionable validity.
Loehlin and Nichols suggest that the higher concordance rates with MZ twins could be due to being
treated the same so it may be due to environment rather than genetics. This is a reasonable
argument as DZ twins tend not to like being treated the same whereas MZ twins are often always
treated the very similar. Twin studies as a whole do show strong genetic evidence for schizophrenia,
however they are never 100% concordant, thus suggest a genetic predisposition rather than a cause
for schizophrenia. Another issue is that twin studies of schizophrenia have small sample sizes;
schizophrenia is evident in 1% of the population and twins with schizophrenia are even rarer, so it is
hard to generalise to the rest of the population and difficult to determine whether these studies are
reliable or not.
Another explanation is the dopamine hypothesis. This proposes that excess levels of dopamine or
oversensitivity of brain neurons may be the cause of schizophrenia. There is evidence to show that
psychosis can be created by the use of amphetamines which increase dopamine activity. Further
evidence comes from antipsychotic drugs that are used to treat schizophrenia which block dopamine
receptors, so preventing dopamine receiving neurons from firing. Also, a drug that is used to treat
Parkinson's disease, which is caused by lack of dopamine, can produce schizophrenic symptoms in
individuals who have no history of the schizophrenic disorder.
The dopamine hypothesis, however, doesn't account for different types of schizophrenia, only
schizophrenia as a whole. A strength of the dopamine hypothesis is that is has been used to devise
effective treatments for relieving schizophrenic behaviour such as Clozapine. However, we cannot
determine whether excess levels of dopamine cause schizophrenia or whether they are caused by
schizophrenia. There iscontradictory evidence for the biochemical explanation provided by Kasper et
al. He suggests that antipsychotic drugs are only effective for positive symptoms of schizophrenia,
therefore excess levels of dopamine can, at best, only explain some types of schizophrenia. He also
suggests that newer A-typical antipsychotic drugs such as Clozapine have proved more effective
than traditional ones in successfully treating the symptoms of schizophrenia despite blocking fewer
dopamine receptors. This suggests there is refuting evidence for dopamine being the main
contributor associated with schizophrenia.
The dopamine hypothesis is biologically deterministic as it assumes that if we have high levels of
dopamine then we must develop schizophrenia, it doesn't take into account factors such as free will.
In contrast to the biological explanation, the psychological explanation would reject the view that
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They are on opposite sides of the Nature vs.
Nurture debate with the psychological explanation supporting nurture, favouring the view that
schizophrenia is caused by life events; our environment, upbringing family etc. E.g. research shows
that dysfunctional family interaction where there is a lot of `expressed emotion' can lead to
schizophrenia. This shows that biological factors are not a sole cause of schizophrenia.…read more