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PsychExchange.co.uk Shared Resource

  1. 1. ‘There is considerable evidence that schizophrenia is caused by biological factors. These can be genetic, neuroanatomical, biochemical, viral or a combination of such factors.’ Discuss biological explanations of schizophrenia. (9 marks +16 marks)The biological explanation of schizophrenia looks at the role of genes, biochemistry, neuroanatomy andinfection. This essay will focus on genetic and biochemical factors in the development of schizophrenia.The genetic explanation of schizophrenia suggests that the disorder is inherited and therefore takes thenurture side of the nature nurture debate. There is much supporting evidence for this. For exampleGottesman conducted a meta-analysis of 40 European studies that allowed him to calculate theconcordance rate of relatives of a schizophrenia sufferer. The percentage risk of developing schizophreniain the general population is 1% but Gottesman found this increased dramatically to 46% concordance foroffspring of two schizophrenic parents and to 48% for monozygotic twins (MZ). Therefore the closer thedegree of relatedness the higher the risk.His findings were challenged when another study found a concordance rate of 6% for dizygotic twinscompared with Gottesmans 17% and a concordance rate of 28% concordance for MZ twins. This reducesthe reliability of Gottesmans study but subsequent studies have produced similar statistics to Gottesmanproving the original study to be robust.It is difficult however to separate the genetic from the environmental factors with these studies. Forexample MZ twins share more similar environments than DZ twins as they are the same sex and thereforemore likely to be treated more similarly. Another issues is that MZ twins share 100% of their genes so whyare they not 100% concordant?Adoption studies are used to help separate genetic from environmental factors. Heston assembled 47adults who had been adopted at birth because their mothers were schizophrenic and a control group of 47adults who were adopted but had normal mothers. They were all interviewed to establish whether theyhad developed the disorder. It was found that 5 of the 47 adoptees from schizophrenic mothers had beenhospitalised with the disorder and none of the control group. Thus supporting the genetic link. The controlgroup was essential for ruling out the possibility that stress and the ensuing environment of adoption wasthe cause of the developing schizophrenia.Although this study appears to conclusively show the link between genetics and schizophrenia there aremethodological issues. For example the study was retrospective meaning that data may have been losttherefore the reliability of the study is challenged. Many of the adults were diagnosed at a time whenclassification of schizophrenia was highly unreliable also challenging the study’s reliability.The reanalysis of data from a number of adoption studies has shown there to be less support for geneticfactors than the original researchers claimed.Research by Crespi has identified 76 genes linked to schizophrenia. However 2/3 of schizophrenics do nothave any relatives with the disorder. Biochemical explanations focus on the role of neurotransmitters inthe brain. For example the dopamine hypothesis states that schizophrenia is caused an excess of theneurotransmitter dopamine at the synapses that use dopamine as their main transmitter. This has beentested through the use of drugs. For example Amphetamines administered to normal control patients inlarge doses can cause amphetamine psychosis the symptoms of which resemble schizophrenia and evensmall doses can increase the severity of symptoms in the sufferers. This is because the drug works bystimulating dopamine transmission in the brain.Phenothiazines are used to alleviate schizophrenia symptoms, the side effects of which resembleParkinson’s disease. As Parkinson’s is associated with low levels of dopamine it suggests the drug works byreducing dopamine levels in the brain.However not all dopamine agonists such as amphetamines increase symptoms in schizophrenics andphenothiazine’s do not alleviate symptoms in all patients which is problematic for the dopamine theory
  2. 2. Biological explanations are reductionist in that they reduce a very complex disorder to something assimplistic as genetic inheritance. It is also determinist in that it does not take into account free willAlthough biological explanations have much support and can provide reasons for the gender differences inonset (males develop schizophrenia earlier due to hormonal changes) environmental and genetic factorsare still difficult to separate. Therefore a diathesis stress approach is appropriate because it states that anygenetic predisposition to the disorder will need an environmental trigger. For example life events such asdeath in the family, as suggested by the psychodynamic approach could be seen as a chronic stressor thatcould trigger psychosis.Examiner CommentThe candidate shows generally accurate and reasonably detailed knowledge of two explanations and arange of relevant research evidence. Understanding of the explanations is reflected in the commentary asmuch as in the outline of the explanations. The commentary is well focused and shows coherent elaborationof most points. Confident use of appropriate terminology.There are a few places where the commentary could be improved by providing more sustained line ofargument. There is no requirement to refer to issues and debates in unit 4 and the ref to reductionism anddeterminism in this script detract rather than add to the quality of the commentary.AO1: 7AO2/3: 14Total for this question: 21 marks = A*

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