Biological explanations for Schizophrenia

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  • Biological explinations
    • Dopamine Hypothesis
      • Increase dopamine
        • It works by flooding the synapse and is temporary
        • Amphetamine is an agonist
        • A Parkinson's drug called L-Dopa increases D and can lead to sz symptoms
      • Decrease dopamine
        • These are anti-psychotic drugs and are antagonists
        • They work by blocking D receptors in the brain and reduce + symptoms
      • Revised D hypothesis
        • + from excess in mesolimbic pathway and - from deficit in PFC
        • Rat study - D depletion in PFC of rats and resulted in cognitive impairment and was reversed by atypical
        • PET scans - found lower levels of D in PFC of sz's
      • The D hypothesis states that an excess of D leads to + symptoms
      • Eval
        • Evidence from drug therapy success as they reduce D
        • Challenges - anti-psychotics don't alleviate symptoms in 1/3 of Ps. In some D levels are normal
        • Inconclusive evidence - amphetamine and cocaine affect other neurotransmitters
    • Genetics
      • Twin Studies
        • MZ share 100% DNA DZ share 50% DNA
        • Joseph - MZ = 40.4% and DZ = 7.4%
        • This suggests that bio is a part of sz
      • Family studies
        • Gottesman - schizo is more common amongst bio relatives with sz
        • 2 sz parents=46% 1 sz    parent= 13% siblings=9%
        • The closer the degree of genetics the greater the risk
      • Adoption studies
        • Tienari studied 164 Finnish adoptees whose bio mothers had sz
        • 6.7% were diagnosed sz compared to 2% of control group
        • This suggests that there is a genetic vulnerability to sz
      • Eval
        • Adoptees may be selectively placed with families with experience of sz
        • MZ twins are treated more similarly and have similar environments
        • The family similarities may be due to parenting patterns not just genes

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