biological explanations

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  • Created on: 06-12-12 11:50
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  • Biological explanations for schizophrenia
    • Biological explanations Genes
      • Twin studies involves mz twins with dz twins
        • This is the idea schizophrenia is inherited through genes
        • Gottesman and shields reviewed results of 5 twins studies looking for concordance rates mz twins 48% chance dz 17%
        • Shows genetic base because mz twins share 100% of genes and dz twins share 50%
      • Adoption Studies involves looking at adopted children who later develop schizophrenia
        • If a biological parent has schizophrenia would suggest genes are more important than environment
        • Tienari study identified 112 children whose bio mother had schizophrenia. compared with 135 adopted children whose mothers had no history of disorder 7% of children whose mother had schiz developed it compared to 1.5% who didn't
        • Rosenthal studied quadruplets in which all 4 girls developed schizophrenia know as genain quads
      • Gene mapping shows several genes are involved in disorder such as 6,9,10,11,18,19
      • Evaluation
        • Methodological problems, difficult to conclusively support the genetic explanation when we examine concordance rates especially looking at mz twins, because if they share 100% of genes the concordance rate should be closer to 100%. Twins studies also produce conflicting results concordance rates range from 58-11% for mz twins
        • Other environmental explanations for schizophrenia must also be considered. It must be remembered that MZ twins also share the same pre natal environment before birth not just the same genes. This means that the role of the environmentally factors can not be entirely ruled out
        • A major problem with adoption studies is 'selective placement'. This involves adoption agencies placing adopted children into families that resemble those of their biological parents in term of educational and social backgrounds. There are implications with this because adoptees share genes in common with biological parents but also raised in an environment which is same as bio family
        • The genetic research is far from conclusive. Tosato et al conducted a review of gene mapping and similar studies concluding that there are several genes indicating susceptibility to schizophreniaThis suggests that schizophrenia does not have a singular genetic cause
    • Biological explanations biochemicals
      • Suggested schizophrenia is caused by excess activity of the neurotransmitter dopamine.
      • Could be too much DA is being released by the pre-synaptic neuron
      • It could be that there are too many DA receptors on the post synaptic, receiving neuron so there is more firing of DA & more DA binds to them
      • The excess of DA activity produces the symptoms of schizophrenia
      • Evaluation
        • There are cause and effect issues we cannot be certain that high levels and activity of dopamine cause schiz or occurs as a result of the disorder if the excessive levels occur as a result of the disorder then we have to look for alternative explanations
        • The biochemical explanation has been accused of being reductionist this is because it reduces a complex disorder to a relatively simple explanation - and imbalance of brain chemical s the biochemical has been accused of being reductionist
        • Excess dopamine cannot explain all schizophrenia symptoms. This is because anti psychotic drugs that block dopamine receptors only reduce the positive symptoms not the negative ones, therefore there must be another explanation for the different subtypes. It is suggested that the excess of dopamine only explains the positive symptoms of schiz not all symptoms
      • This theory was developed after it was discovered anti-psychotic drugs reduce symptoms of schizophrenia prevent presynaptic dopamine neurons from firing and releasing dopamine
      • Amphetamines have also helped research biochemical basis as they increase dopamine levels in the brain, high doses of this drug produces schizophrenia like symptoms and they increase symptoms for schizophrenics
      • There is conflicting research evidence for the dopamine hypothesis. Jackson 1986 compared dopamine levels between drug free schizophrenic and controls. He found no difference between DA levels in the 2 groups which contradicts the dopamine hypothesis


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