Schizophrenia Biological explanations

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  • Biological Explanations
    • Dopamine Hypothesis
      • Theory
        • Excess dopamine activity at synaptic sites
          • Due to high number of D2 receptors on receiving neurones
            • More dopamine binding so more neurones firing.
        • Dopamine is a neurotransmitter
          • controls: movement, social functioning, memory and cognition, mood
          • Causes positive symptoms of schizophrenia
      • Research
        • Support
          • Seeman
            • Post Mortem - Densities of D2 receptors average 20pmol/g on schizophrenics, this is 50% more than controls.
              • Cannot infer cause and effect
          • Grilly
            • L-dopa (Parkinson's medicine) raises dopamine levels and causes schizophrenic symptoms
          • Amphetamine
            • Dopamine agonist - causes hallucinations and delusions
          • Biological treatments
            • Chlorpromazine blocks dopamine receptors and removes symptoms.
        • Limitations
          • Amphetamine
            • only mimics positive symptoms, so only explains 1/2 schizophrenia
              • Dopamine cannot be the only cause, possibly another neurotransmitter e.g. serotonin
          • Atypical anti-psychotic drugs only cure positive symptoms
            • Dopamine cannot be the only cause, possibly another neurotransmitter e.g. serotonin
    • Enlarged ventricles
      • Theory
        • Ventricles are naturally occurring spaces in the brain containing cerebral fluid
        • Torrey
          • Schizophrenics have 15% bigger ventricles
      • Research
        • Support
          • Andreasen
            • CT scans - significant enlargement in schizophrenics.
        • Limitations
          • Coplov and Crook
            • 90 CT scans, overlap between normal and schizophrenics.
          • Cause or effect? Caused by medicine?
            • Lyon
              • Increased medication = increased ventricles
    • Genetics
      • Theory
        • Gene for SZ passed on in DNA from parent to child.
          • If correct a pattern should be seen.
            • Same genes = normally same environment
      • Research
        • Support
          • Family Studies
            • Moldin
              • Reviewed twin studies between 1920-1987.
                • MZ = 46%, even when reared apart. DZ = 14%
            • Gottesman
              • 40 twin studies, MZ concordance = 48%, DZ = 14%
                • All more than 1% of general population.
                • MZ not 100%, must be another factor. Diathesis stress model?
                • MZ treated more similarly
                  • DZ = 14%, siblings = 9%. Same genes shared. DZ treated more similarly than siblings.
            • When diagnosing twins researchers may be bias if they know if they are MZ or DZ
          • Adoption Studies
            • Tienari
              • 164 adopted children, SZ mothers. 8.1% children with SZ mothers got schizophrenia 2.3% controls.
                • Genes only activated in poor communication families
            • Heston
              • 47 children SZ mothers, adopted at 2 months
                • 17% test group got SZ, 0% control
                  • May have had a traumatic experience before adoption
            • Adoptive parents informed on background. Who would adopt these children?
        • Limitation
          • No specific gene found. 12 genes implicated.

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