Biological Explanation for Schizophrenia

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  • Created on: 20-03-14 08:36
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  • Biological Explanation for Schizophrenia
    • Dopamine Hypothesis Explanation
      • Abnormally high levels of dopamine receptors at the synapse
      • Increased dopamine in the mesolimbic pathway contributes to positive symptoms
      • Increased dopamine in the mesocortical pathway contributes to negative symptoms
      • Neurons that use the transmitter 'dopamine' fire too often and transmit too many messages or too often
      • Certain D2 receptors are known to play a key role in guiding attention.
      • Lowering dopamine activity helps remove the symptoms of schizophrenia
    • Dopamine Hypothesis Evaluation
      • Role of Drugs
        • Strength because shows dopamine produces symptoms
        • Amphetamines (agonists) lead to increase in DA levels
        • Large quantities lead to delusions and hallucinaions
        • If drugs are given to schizophrenic patient their symptoms get worse
      • Parkinson's Disease
        • Strength because shows dopamine produces symptoms
        • Parkinson's sufferers have low levels of dopamine
        • L-Dopa raises DA activity
        • People with Parkinson's develop schizophrenic symptoms if they take too many L-Dopa
        • Chlorphromazine (given to schizophrenics) reduce their symptoms by bloacking DZ receptors
      • Post Mortem
        • Strength because increased dopamine receptors in schizophrenicsa
        • Autopsies have found that people with schizophrenia have a larger than usual number of dopamine receptors
        • Increase of DA in brain structures and receptor density (left amygdala and caudat ncleus putamen)
        • Concluded that DA production is abnormal for schizophrenia
      • PET Scans
        • Weakness because shows drugs don't reduce symptoms
        • PET scans have suggested that drugs didn't reduce symptoms of patients diagnosed with disorder for 10 years or more
        • Farde et al (1990)
          • No difference in the number of dopamine receptors between schizophrenics and controls
      • Negative Symptoms
        • Weakness because drugs don't help these syptoms
        • Not good at explaining negative symptoms
        • Suggested that type 2 is related to a different king of abnormality such as brain structure
    • Genetic Factors
      • Family Studies
        • Gottesman (1991)
          • Schizophrenia is more common in biological relatives, the more closely related, the higher the risk.
          • The concorndance rate among identical MZ twins is 48% and DZ fraternal twins is 17%
      • Adoptive Studies
        • Kety et al (1988)
          • Found 14% of biological relatives of adopbtees were classified at schizophrenic
          • Only 2.7% of adoptive relatives were found to be schizohprenic


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