Biological Explanations of SZ.
- Created by: Jessica Harrington
- Created on: 12-03-13 18:03
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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.
- Gottesman: MZ twin- 48% MZ twins bought up apart had similar concordance. DZ twins- 17%
- 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.
- Tienari: FInnish mothers with sz given children up for adoption. 10% children developed sz, compared to 1% adopted children control group.
- Twin Studies
- 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.
- 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.
- 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.
- Dopamine Hypothesis: sz patients have exessive levels of dop or brain is extra sensitive to effects of dop.
- 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.
- Brain lesions occur in early development & can make child vulnerable to 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.
- Genetics
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