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1. Schizophrenia explanations <ul><li>Biological </li></ul><ul><ul><li>Genetics…
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  • 1. Schizophrenia explanations <ul><li>Biological </li></ul><ul><ul><li>Genetics </li></ul></ul><ul><ul><li>Neurochemicals & hormones </li></ul></ul><ul><ul><li>Structural brain abnormalities </li></ul></ul><ul><li>Psychological </li></ul><ul><ul><li>Family dynamics </li></ul></ul><ul><ul><li>Life stress </li></ul></ul><ul><ul><li>Urbanicity </li></ul></ul>
  • 2. Assumption of biological explanations <ul><li>All mental disorders have a physical cause. (micro-organisms, genetics, biochemistry or neuroanatomy) </li></ul><ul><li>Metal illnesses can be described in terms of clusters of symptoms. </li></ul><ul><li>Symptoms can be identified, leading to the diagnosis of an illness. </li></ul><ul><li>Diagnosis leads to appropriate physical treatments. </li></ul>
  • 3. Schizophrenia: Biological <ul><li>Genetics </li></ul><ul><li>Structural brain abnormality </li></ul><ul><li>Neurochemistry (Dopamine hypothesis) </li></ul>
  • 4. Schizophrenia: genetics <ul><li>Prevalence of schizophrenia is the same all over the world (about 1%) </li></ul><ul><ul><li>Supports a biological view as prevalence does not vary with environment </li></ul></ul><ul><ul><li>However, there are variations within broad geographical areas (e.g. Torrey 2002 – Croatia & Ireland) </li></ul></ul><ul><ul><li>Urbanicity data </li></ul></ul>
  • 5. Schizophrenia: genetics <ul><li>Family, twin and adoption studies have suggested that genetics play a major role in the transmission of schizophrenia. Irwing Gottesman compiled over 40 studies in order to work out the risks of developing schizophrenia, of people with different familial relationships to the schizophrenic person. </li></ul>
  • 6. Schizophrenia: genetics <ul><li>Gottesman and Shields reviewed the results of 5 twin studies looking for concordance rates for schizophrenia (4). </li></ul><ul><li>It was found that in MZ twins there was a concordance rate of 35-58% compared with dizygotic (DZ) twin rates that ranged from 9-26%. They also found a concordance rate in MZ twins of 75-91% when the sample was restricted to the most severe form of schizophrenia (5). </li></ul>
  • 7. Schizophrenia: genetics <ul><li>The milder forms of schizophrenia had concordance rates of 17-33% suggesting that there may be greater genetic loading with severe forms of schizophrenia. The twin studies have all assumed that the shared environmental effects for MZ and DZ twins are equal which may be incorrect </li></ul>
  • 8. Schizophrenia: genetics Source: Gottesman (1991)
  • 9. Schizophrenia: genetics <ul><li>Risk rises with degree of genetic relatedness </li></ul><ul><ul><li>Spouse – 1% (same as G.P.) </li></ul></ul><ul><ul><li>Child – 13% </li></ul></ul><ul><ul><li>DZ twin – 17% </li></ul></ul><ul><ul><li>MZ twin – 48% </li></ul></ul><ul><li>Effect of shared environment? </li></ul>
  • 10. Schizophrenia: genetics <ul><li>Adoption studies </li></ul>Prevalence amongst biological relatives Prevalence among adoptive relatives Kety et al (1968) schizophrenia only 13% 2% Tienari et al (1994) all ‘severe’ psych. diagnoses 30% 15%
  • 11. Schizophrenia: genetics <ul><li>Look in Gross and Rolls, Cardwell A2, Nelson Thorne and Eysenck texts </li></ul><ul><ul><ul><li>Rosanoff et al 1934 </li></ul></ul></ul><ul><ul><ul><li>Kallaman 1946 </li></ul></ul></ul><ul><ul><ul><li>Gottesman and Shields 1966 </li></ul></ul></ul><ul><ul><ul><li>Fischer 1973 </li></ul></ul></ul><ul><ul><li>What do these studies suggest? </li></ul></ul><ul><ul><li>You have 15 minutes </li></ul></ul>
  • 12. Schizophrenia: genetics <ul><li>Substantial evidence for a genetic contribution </li></ul><ul><li>Some evidence disputed: </li></ul><ul><ul><li>Shared environment issues </li></ul></ul><ul><ul><li>Diagnostic criteria in adoption studies </li></ul></ul><ul><li>All the evidence also suggests environmental triggers </li></ul>
  • 13. Schizophrenia: genetics <ul><li>Vast variation in concordance rate across the studies which could suggest a different diagnostic procedure </li></ul><ul><li>69% still leave much room for environmental influences. </li></ul><ul><li>However the concordance rate in MZ twins is still 5X greater than in DZ twins. </li></ul><ul><li>This lead researcher to carry out adoption studies </li></ul><ul><ul><li>Heston 1966 </li></ul></ul><ul><ul><li>Kety et al 1975 </li></ul></ul>
  • 14. Genetics. Evaluation <ul><ul><ul><li>Support evidence for twin and adoption studies </li></ul></ul></ul><ul><ul><li>Heritability is similar with other major disorders such as breast cancer, hypertension, etc </li></ul></ul><ul><ul><li>How is schizophrenia inherited and what exactly is inherited? </li></ul></ul><ul><ul><li>Is schizophrenia a single or multiple disorder </li></ul></ul>
  • 15. Genetics. Evaluation <ul><li>The influence of environmental factors </li></ul><ul><li>Diathesis stress </li></ul><ul><ul><li>Vulnerability </li></ul></ul><ul><ul><li>See Cardwell p318-19 for this + additional texts and notes on environmental factors to develop your evaluation. You have 10 minutes </li></ul></ul>
  • 16. Schizophrenia: Biochemical <ul><li>The dysfunction of several neurotransmitter systems </li></ul><ul><ul><li>Dopamine, </li></ul></ul><ul><ul><li>5-hydroxytryptamine (5-HT; Serotonin) </li></ul></ul><ul><ul><li>Glutamate </li></ul></ul><ul><li>are thought to play a part in schizophrenia. </li></ul><ul><li>We will concentrate on the Dopamine Hypothesis </li></ul>
  • 17. Schizophrenia & dopamine <ul><li>The dopamine hypothesis: </li></ul><ul><ul><li>Schizophrenia is caused by excessive DA activity. </li></ul></ul><ul><ul><li>This causes abnormal functioning of DA-dependent brain systems, resulting in schizophrenic symptoms </li></ul></ul><ul><ul><li>DA can increase or decrease brain activity depending on the system you’re looking at </li></ul></ul>
  • 18. The dopamine hypothesis <ul><li>Wise & Stein (1973) report abnormally low levels of DBH in post-mortem studies of Schizophrenic patients. </li></ul>
  • 19. The dopamine hypothesis <ul><li>Overdose of amphetamine (DA agonist) can produce S-like symptoms. S patients have abnormally large responses to low amphetamine doses </li></ul><ul><ul><li>Suggests a role for DA in S symptoms </li></ul></ul><ul><ul><li>Suggests that the issue is over-sensitivity to DA rather than excessive DA levels </li></ul></ul>
  • 20. The dopamine hypothesis <ul><li>Symptoms can be treated with DA antagonists (e.g. chlorpromazine). These are effective in 60% of cases with more impact on positive symptoms. </li></ul><ul><ul><li>Supports role of DA again, but what about 40% who don’t respond? </li></ul></ul><ul><ul><li>Lack of impact on negative symptoms hints at two separate syndromes </li></ul></ul>
  • 21. Biology and Schizophrenia <ul><li>Consistent evidence for abnormal brain functioning in Schizophrenia patients but no single factor identified. </li></ul><ul><ul><li>Two syndromes? One caused by DA activity & associated with +ve symptoms; other caused by brain degeneration & associated with –ve symptoms. </li></ul></ul><ul><ul><li>Cause & effect issues everywhere </li></ul></ul><ul><ul><li>Confounding effects of drug treatment </li></ul></ul>
  • 22. Biochemical Evaluation <ul><li>The evidence therefore comes from 3 areas: </li></ul><ul><li>Post mortems on schizophrenics who show unusually high levels of dopamine </li></ul><ul><li>The anti-schizophrenic drugs work by binding to the Dopamine receptor sites and prevent them form taking up excessive amount of dopamine. Tough sides effects similar to those symptoms seen in Parkinson's are seen to occur. </li></ul><ul><li>High does of L-dopa used to treat PK can sometime produce symptoms very similar to psychomotor disorders like schizophrenia. </li></ul>
  • 23. Biochemical Evaluation <ul><ul><ul><ul><li>Inconclusive evidence. Cause or effects? Dopamine cannot explain all cases. Incomplete explanation. Other neurotransmitter could be present such as glutamate. </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Reductionist </li></ul></ul></ul></ul><ul><ul><ul><ul><li>PET scan show increased levels of dopamine </li></ul></ul></ul></ul>
  • 24. Biochemical Explanation <ul><li>Now go to the textbooks and find out additional information on the Biological explanation. </li></ul><ul><li>Use the following texts: </li></ul><ul><ul><li>Cardwell, Eysenck, Lewis, Cardwell & Flannigan, AQA Text </li></ul></ul><ul><li>Write an account of this explanation and its evaluation in your own words. You have 20 minutes </li></ul>
  • 25. Other possible causes <ul><li>Brain structure </li></ul><ul><li>Brain damage </li></ul><ul><li>Viral infection </li></ul><ul><li>Birth complications </li></ul>
  • 27. Brain structure <ul><li>Swayze (1990) reviewed 50 studies of schizophrenics and found that many had abnormally large amounts of liquid in the cavities of the brain. Suddath, who supports this found the same enlarged cavities when using MRI scans on schizophrenic twins. Other structural abnormalities include : </li></ul>
  • 28. Structural abnormalities <ul><li>Unusually large corpus collosum </li></ul><ul><li>High density of white matter in the right frontal and parietal lobe </li></ul><ul><li>Small amount of grey matter in the temporal lobes </li></ul><ul><li>A change in blood flow in the cerebral hemisphere </li></ul><ul><li>MRI scan show unusually large ventricular enlargement but this is also seen in non-schizophrenics </li></ul><ul><li>Hippocampus and the thalamus are all affected in the brains of schizophrenics </li></ul>
  • 29. 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>
  • 30. 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>
  • 31. Ventricular Enlargement
  • 32. Activity <ul><li>Using page 316-7 </li></ul><ul><li>Outline the evidence that support brain abnormalities. </li></ul><ul><li>Evaluate this evidence. </li></ul><ul><li>You have 10 minutes: </li></ul>
  • 33. Brain Damage <ul><li>Decreased rate of blinking </li></ul><ul><li>Staring </li></ul><ul><li>Lack of the blink reflex in response to a tap on the forehead </li></ul><ul><li>Poor visual pursuit movements </li></ul><ul><li>Poor pupil reactions to light </li></ul>
  • 34. Viral Infection <ul><li>In recent years, there has been a build up of evidence supporting the role of viral infections in the development of schizophrenia, including the poliovirus, the flu virus and a virus called encephalitis lethargica ('inflammation of the brain that makes you tired‘). </li></ul>
  • 35. Birth Complications <ul><li>Complications during pregnancy, abnormal foetal growth and complications during delivery are significant risk factors in the development of schizophrenia. Those that play a significant role in the development of schizophrenia include: </li></ul><ul><li>bleeding, diabetes and pre-eclampsia pregnancy complications  </li></ul>
  • 36. Birth Complications <ul><li>abnormal foetal growth and development problems including conditions such as low birth weight and reduced head circumference  </li></ul><ul><li>complications of delivery including asphyxia (lack of oxygen) and emergency Caesarean section </li></ul><ul><li>However, the effect of such complications is small in comparison with factors such as genetic pre-disposition to schizophrenia. </li></ul>
  • 37. Activity <ul><li>Using page 318-9 </li></ul><ul><li>Evaluate the birth complication and pregnancy explanation for schizophrenia. </li></ul><ul><li>Outline and assess the following suggestions: </li></ul><ul><li>Substance abuse is linked to schizophrenia. </li></ul><ul><li>Environmental stressors (Diathesis stress model) are a possible cause of schizophrenia. </li></ul><ul><li>Consider / list the AO3 issues relating to the biological explanations. </li></ul>
  • 38. TASK: Exam Question: <ul><li>PLAN THE QUESTION </li></ul><ul><li>Outline and evaluate one or more biological explanations for schizophrenia. (25 marks) </li></ul>
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