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1. Schizophrenia 2. Explanations – Biological vs Psychological Nature vs Nurture 3. Biological Explanations <ul><li>Genetics…
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  • 1. Schizophrenia
  • 2. Explanations – Biological vs Psychological Nature vs Nurture
  • 3. Biological Explanations <ul><li>Genetics </li></ul><ul><li>Bio chemicals </li></ul><ul><li>Brain Structure </li></ul>
  • 4. Genetics – Twin Studies <ul><li>Gottesman 1991 suggests that schizophrenia is inherited through genes. Studied 40 twins - the concordance rate for MZ twins is about 48% and only about 17% for DZ twins. </li></ul><ul><li>Also Cardno 2002 – showed concordance rate of 26.5 MZ and 0% for DZ. </li></ul>
  • 5. Evaluation – Twin Studies <ul><li>However, the fact that the concordance rate for twins is not 100% means that Schizophrenia cannot be accounted for by genetics alone </li></ul><ul><li>As we already know, the higher concordance between MZ twins could be explained by greater environmental similarity rather than genetic similarity – MZ twins elicit more similar treatment than DZ twins (so can be explained by other theories) </li></ul><ul><li>Also the sample size of such twin studies is always going to be very small, so …….. </li></ul>
  • 6. Further Twin Evaluation <ul><li>Twin studies do not all use the same diagnostic criteria – Therefore different diagnosis will produce different concordance rate. </li></ul><ul><li>Concordance rates can also be calculated differently depending on the method used – questions the reliability of such studies. </li></ul>
  • 7. Genetics - Adoption Studies <ul><li>Tienari – 155 adopted children – who biological mothers had schizophrenia –they had a concordance of 10% compared to 1% in adopted children without schizophrenic parents. </li></ul><ul><li>This is very strong evidence that genetics are a risk factor for schizophrenia </li></ul>
  • 8. Genetics – Family Studies <ul><li>Gottesman also studied families – he concluded that if both your parents suffer from Schizophrenia, then you have a 46% chance of developing it yourself (compared to a 1% chance of someone selected at random will suffer) </li></ul><ul><li>The more genetically similar relatives are, the more concordance is found. </li></ul>
  • 9. Family Evaluation <ul><li>This evidence again strongly suggests genetics is a factor </li></ul><ul><li>However: </li></ul><ul><li>It could also be explained in terms of the fact that genetically similar family members tend to spend more time together and so environment could also affect. </li></ul>
  • 10. Biochemical Factors – The Dopamine Hypothesis <ul><li>This theory claims that excessive amounts of dopamine or an oversensitivity of the brain to dopamine is the cause of schizophrenia </li></ul><ul><li>Eval: There is strong empirical support which suggests that dopamine plays an important role in schizophrenia – e.g drugs which block dopamine (Phenothaiazines) also seem to reduce the symptoms of schizophrenia. </li></ul>
  • 11. The Dopamine Hypothesis - Evaluation <ul><li>L-Dopa – a drug for Parkinson’s disease actually increases dopamine – this in turn can produce symptoms of schizophrenia. </li></ul><ul><li>Post mortems of schizophrenics, show an increase of dopamine in parts of the brain. (Seeman 1987) </li></ul>
  • 12. Dopamine Evaluation - Negatives <ul><li>Phenothiazines do not seem to work for everyone therefore.... </li></ul><ul><li>Cause or effect? </li></ul><ul><li>This theory is over simplistic and has been criticized for using the treatment to determine the cause. This is an AETIOLOGY FALLACY </li></ul>
  • 13. Neuroanatomy - Brain Structure <ul><li>There is growing evidence that schizophrenia is down to physical abnormalities in the brain. </li></ul><ul><li>Szesko et al found that the ‘asymmetry’ found in normal brains – in the prefrontal cortex is absent in people with schizophrenia. </li></ul>
  • 14. Brain Structure <ul><li>People with schizophrenia have abnormally large ventricles in the brain. Ventricles are fluid filled cavities. This means that the brains of schizophrenics are lighter than normal. </li></ul>
  • 16. Brain Structure Evidence <ul><li>Andreasen et 1990 – conducted a very well controlled CAT scan study and found significant enlargement of the ventricles in schizophrenics compared to controls. </li></ul><ul><li>However this was only the case for men and not for women. Therefore cant generalise to everyone. </li></ul>
  • 17. Evaluation <ul><li>Research is difficult to interpret and there have been contradictory findings. </li></ul><ul><li>Difficult to establish cause and effect – as many participants have suffered from schizophrenia for a while and have been undergoing treatment. So....... </li></ul>
  • 18. Further Evaluation <ul><li>The main problem with such studies is that it is not found in all schizophrenics. This has lead to further research done by Crow 1985. </li></ul><ul><li>He suggested two types of schizophrenia with two biological causes. </li></ul>
  • 19. Two Syndrome Hypothesis - Crow 1985 <ul><li>Type one - genetically inherited associated with dopamine – characterised by positive symptoms. </li></ul><ul><li>Type Two – Neurodevelopmenal disorder – to do with Brain structure – characterised by negative symptoms. </li></ul>
  • 20. Summery <ul><li>Biological explanations do account for schizophrenia, however the fact that there is no conclusive explanation that accounts for all schizophrenics – psychological explanations need to be considered. </li></ul>
  • 21. Exam Question <ul><li>TASK: Exam Question: PLAN THE QUESTION </li></ul><ul><li>Outline and evaluate one or more biological explanations for schizophrenia. In your evaluation you should refer to research evidence. (25 marks) </li></ul>
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