Biological explanations for scizophrenia

Dopamine Hypothesis
1. Parkinson's Disease
  1. Grilly 2000- found that people taking L-dopa drugs (raises dopamine levels) developed schizophrenia
  2. Timmons and Hamilton 1990- found very few schizophrenics suffer with Parkinson's disease.
2. Anti-psychotic Drugs
  1. Barlow and Durand 1995- reported that chlorpromazine reduces schizophrenic symptoms in 60% of cases. Mainly impacts on positive symptoms rather than negative
  2. Haracz 1982- found high dopamine levels in postmortems in schizophrenics who had taken medication shortly before death. Schizophrenics not on medication had normal levels.
  3. Davis 1978- found that it takes weeks for the drugs to work, even though dopamine activity gets blocked immediately
3. High Levels of Dopamine
  1. Jackson 1986- found no evidence of high dopamine levels in schizophrenics
  2. Wise and Stein 1973- low levels of dopamine Beta hydroxylase in schizophrenics who had dies in accidents
4. Amphetamines
  1. Janowski et al 1972- low doses in normal control produced slight agitation. In schizophrenics, symptoms became worse.
  2. Timmons and Hamilton 1990- report high doses result in healthy people displaying schizophrenic behaviour
Enlarged Ventricles
1. Torry 2002- on average, the ventricles of a schizophrenic are on average, 15% larger than a healthy person
2. Bornstein et al 1992- schizophrenics with enlarged ventricles are more likely to display negative symptoms, rather than positive symptoms and don't respond well to anti-psychotics
3. Copoloy and Crook 2000- meta analysis of over 90 studies with CT scans revealed a substantial overlap between schizophrenics and control populations of ventricle size.
4. Lyon et al 1991- found that as the dose of anti-psychotic drugs increased, the density of brain tissue decreased, leading to enlarged ventricles.
Genetics
1. Adoption Studies
  1. Tienari et al 2000- looked at 164 adoptees with biological schizophrenic mothers, but only 12 (6.7%) were later diagnosed with schizophrenia. However, 194 adoptees were looked at as a control and 4 (2%) were also diagnosed
  2. Most adoption studies looking into schizophrenia broaden the definition of schizophrenia to non-psychotic schizophrenia spectrum to get to significant results
  3. There is an assumption of adoption studies that the parents who adopt children from a schizophrenic background are the same as those who adopt children with a normal biological background
  4. Kety et al 1978- looked at adopted children in Finland who had developed schizophrenia. They found that their biological parents were more likely to have schizophrenia than the parents who adopted the child and raised them.
2. Twin Studies
  1. Gottesman and Bertelsen 1989- they found that if your parent had an identical twin who had schizophrenia, you have a 17% chance of developing it too. However, if your parent doesn't have the disorder but the other twin does, then you still have a 17% chance of getting schizophrenia.
    1. Due to the fact that this study was constructed over 20 years ago, it's harder to generalise to public now. Also, it was difficult to tell if twins were MZ or DZ, so the results may not actually be accurate.
  2. Gottesman and Shields 1972- looked at 57 schizophrenics between 1958 and 1964. 40% MZ and 60% DZ. If one twin had schizophrenia but the other didn't, it was followed for 13 in case they developed it later. Concordance eate for MZ was 42% and DZ 17%.
    1. Heston 1970- found that if one MZ twin had schizophrenia, there is a 90% probiblility that other twin will have some sort of mental disorder.
      1. Suggests that there is a genetic link for schizophrenia but there are other factors, otherwise concordance rate would be 100%

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Biological explanations for scizophrenia

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