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Wednesday, 11 July 2012

Schizophrenia, Nature vs Nurture

Why do we question the purely Biological explanation of Schizophrenia and believe the environment play a significant role too?

The reasons why we question whether Schizophrenia is Biological or due to the environment is because there is not an 100% concordance rate, this shows that it cant be completely explained by genes and schizophrenia could be developed due to a pre-disposition to the disorder that makes the individual more at risk. This leads to us suggesting that a biological explanation cant account for a full and justified explanation for the development of schizophrenia.


However, the Biological explanation has clearly got allot to do with the development of Schizophrenia. Dopamine is a neurotransmitter that causes neurones to fire, the hypothesis about dopamine was that Schizophrenics have a excessive amount that causes the neurones to fire more often so they transmit to many messages. It is said that this excessive amounts of dopamine is the reason for many symptoms of the disorder, this is justified by the fact that amphetamines increase the amounts of dopamine as this gives people without the disorder similar behaviour to a paranoid Schizophrenic when given in large doses and small doses make the symptoms of a Schizophrenic worse. Anti psychotic drugs that treat Schizophrenia give further evidence for the relationship between Schizophrenia and Dopamine, the work by blocking Dopamine receptors so they prevent dopamine-receiving neurones from firing.

There is another explanation based around Dopamine that suggests instead of there being excessive dopamine there is simply more dopamine receptors so they lead to more firing and therefore more messages are sent.

Autopsies have found there are generally a large number of dopamine receptors and an increase amount of Dopamine in the left amygdala and increased Dopamine in the caudate nucleus and putamen.

Miyakawa et al.(2003) studies DNA from human families that had been affected by Schizophrenia, they found that those with the disease were more likely to have a defective version of the gene PPP3CC which is associated with the production of calcineurin which regulates the immune system.

Sherringtion et al.(1988) has found a gene located on chromosome 5 that has been linked in a small number of extended families where they have the disorder, this not only shows a Biological and genetic reason for the development of Schizophrenia but also shows that it can be passed on down to generations.

Suddath et al.(1990) he used MRI (magnetic resonance imaging) to obtain pictures of the brain of Monozygotic twins in which only one twin was Schizophrenic. He found that the Schizophrenic twin generally had more enlarged ventricles (in the brain) and reduced anterior hypothalamus, this difference was so large that the Schizophrenic twins could be easily spotted by looking at the bran images in most pairs suggesting there is a wider academic credibility for enlarged ventricles determining the likelihood of Schizophrenia developing.

Research in providing evidence for the Biological explanation has high reliability as the research is carried out in highly controlled environments with high tech and scientific equipment such as the MRI and PET scanners. These provide accurate readings of brain regions such as the frontal and pre-frontal cortex, the basil ganglia, the hippocampus and the amygdal. This suggests that if this research was tested and re-tested the same results would be achieved.

Structural abnormalities have been found more often in those with negative/chronic symptoms than positive/acute symptoms which help lead to the idea of there being two types of Schizophrenia.

Is the raised levels of Dopamine the cause of Schizophrenia or is it a result? It is not clear which comes first so one needs to be careful when establishing cause and effect relationships in patients.

                                                   Family Studies, Twin Studies.

Family studies:
First degree relative have on average 50% of their genes where second degree relatives have around 25% shared. Studies compare the rates of Schizophrenia in relatives of diagnosed cases compared to relatives of the control (that don't have the disorder). The evidence suggests that the closer the biological relationship, the greater the individuals risk of developing Schizophrenia.

Twin studies:
offer an alternative way of establishing genetic links, by comparing the difference in concordance rates. Both share the same environment, but only MZ twins have identical make up, many studies have been conducted and they all show a much high concordance rate in MZ twins than DZ twins. MZ twins that have been reared apart are useful to separate the effects of genetics and environment, when one of the is Schizophrenic. Gottesman and Sheilds (1982) used the Maudsley twin register and found that 58% were concordant with Schizophrenia. This means that if the genetic hypothesis is correct then the offspring of a non-affected discordant MZ twins should be at high risk.Fisher (1971) found that 9.4% of such offspring developed schizophrenia, which is a higher incidence that the general population which ranges at about 1% to 2%. A study in London found a 40% concordance rate in MZ twins and a 5.3% in DZ twins.


Thanks for reading,
adoption studies, explanations of schizophrenia and treatments will be uploaded soon.

Kyah Sisulu

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