Biological Explanations of SZ.

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  • Biological Explanations of SZ.
    • Genetics
      • Twin Studies
        • Gottesman: MZ twin- 48% MZ twins bought up apart had similar concordance. DZ twins- 17%
          • If genetics was sole cause MZ would be 100%
        • Recent findings on News say 4 genes linked to disorders including sz.
      • Family Studies
        • Gottesman:  2 parents- 46%  1 parent- 16% someone selected at random- 1%
        • Kety et al: children matched on age, gender, parent socio-economic status, urban/rural residence. sz 16% high risk group, 2% low risk group.
          • Follow up issue, longitudinal study issue, smaller sample size of low risk group so less representative.
        • Difficult to interpret due to nature and nurture working together,
      • Adoption Studies
        • Tienari: FInnish mothers with sz given children up for adoption. 10% children developed sz, compared to 1% adopted children control group.
          • Culture bias.
        • Children are sometimes adopted by members of extended family or keep in contact with bio parents.
    • Neurotransmitters
      • Dopamine Hypothesis: sz patients have exessive levels of dop or brain is extra sensitive to effects of dop.
        • Cure came before explanations so hypo is based on success of treatment.
        • ANti-psychotic drufs block dop receptors.
          • Wong et al: 2-fold increase in density of dop receptors in sz patients who never been treated with drugs compared to patients who been treated with drugs.
            • Drugs reduce dop leves and are successful in curing symptoms therefore dop is a factor.
            • Individual difference alters outcome of drugs. Cause and effect issue. What causes difference in dop levels.
        • L-dopa increases dop levels.
          • When given to patients with Parkinsons has presented unwanted side effects of sz symptoms.
        • Anphetamine produces a functional excess of dop so the brain responds as if there is too much of it.
          • Timmons & Hamilton: high doses of amph can result in acute psychosis resembling sz in clinically normal people.
          • Sz patients's symptoms get worse when given amph.
        • Post-mortem examinations showed sz patients had greater density of dop receptors in certain parts of brain.
        • It is hard to access brain levels of dop in sz patients.
          • Indirectly by inserting small needle into the spine (can be dangerous)
          • Directly by most- mortem.
        • Casuality issue, what causes excessive levels of dop in first place.
        • Hypothesis too single-minded for proper explanation.
    • Neurodevelopment
      • Brain lesions occur in early development & can make child vulnerable to sz.
        • Brain lesions caused by flu in 3rd trimester in pregnancy & being born in winter.
      • Birth complications like premature birth, low birth weight, prolonged labor and fuetal distress also associated with sz.
    • Neuroanatomy
      • Techniques used for studying brain include MRI scans.
      • Sz patients have enlarged ventricals in the brain due to surrounding brain areas decreasing in volume.
        • Data is correlation. Cause and affect issue.


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