Aetiologies of Schizophrenia:


Introduction & biological explanations

  • There are 3 types of schizophrenics: Paranoid, catatonic and disorganised.
  • Also catergories for schizophrenia: type 1 (positive symptoms) - hallucinations, delusions and thought disorder (the inability to connect with real life). Type 2: (negative symptoms) - inability to work i.e. hold down a job, participant in normal social settings and lack of emotional sensitivity.
  • Prevalence rates range from around 0.2% - 2%.

Biological explanations:

  • Adoption studies: Tienari - looked at children with biological mothers with schizophrenia compared with adopted children with schizophreic tendancies - he then looked back 18 years later and found that group 1 ... % of the children had schizophrenia, wheras group 2 only had 1.5% - control group.
  • Twin studies: Joseph (2003) : found high prevelance rates for schizo in MZ twins(40%) compared with only 7% for DZ twins, although concordance rates were nowhere near 100% -meaning that there must also be environmental factors that trigger the disorder. & MZ twins share a more similar environment than DZ twins.
  • Gottesman et al found 58% (7/12) twins reared apart were concordat for schizophrenia.
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Neurologiclal explanations & dopamine:

  • Brain abnormalities have been found in schizophrenics with enlarged ventricles.
  • Not clear if these proceed in the onset of schizophrenia, or if they're an effect of the treatment for schiophrenia - although no cause and effect relationship can be inferred.
  • Rapoport (1997) - looked at children & the onset of schizo and found that the children who developed schizophrenics had large ventricles prior to the onset.

Dopamine Hypothesis:

  • States that schizophrenia is caused by excess dopamine - phenothazines reduce dopamine activity in the brain.
  • Won et al (1986) carried out PET scans & found that the density of dopamine receptors were greated in schizophrenics.
  • Although neuropletic drugs can only reduce the positive symptoms - there is also a delay in the relief effect.
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Family Stresses & Expressed Emotion (EE):

  • Faulty families have been found in schizophrenics - Bateson's doubld-bind study states that parents that give their children confusing/conflicting messages make the child confused & they have self-doubt - the evidence is correlational.

Expressed Emotion (EE):

  • Brown - found that schizophrenics returning to high EE families (when families are too over concerning etc) were more likely to relaspe. 
  • Vaugh & Leff - found that schizophrenics with loww EE families, were likely to relapse 13% of the time, whereas schiophrenics with high EE families were 51% more likely to relapse.

Diathesis-stress model:

  • Suggested that schizophrenia may exist with a biological predispostion and that stressors may trigger schizophrenia - these could be major life events//traumatic times.
  • Tienari et al found that all schizophrenics that he had researched had disturbed family backgrounds.
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