Biochemical Factors: Dopamine Hypothesis

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Biochemical Factors: Dopamine Hypothesis

Advantages

  • Amphetamines give similar symptoms to those of excess dopamine
  • Phenothiazines block dopamine receptors and reduce schizophrenic symptoms
  • Schizophrenics are more sensitive to dopamine uptake
  • Drugs to increase dopamine production in sufferers of Parkinson's disease give psychotic symptoms
  • Some genes link with dopamine production and are found with greater frequency in those with Schizophrenia
  • Brain differences might link with dopamine sensitivity
  • Supporting studies, e.g. Lindstroem found that IDOPA was used more quickly in the schizophrenics, suggesting that they make more dopamine
  • Donnelly found that schizophrenics have more homovanillic acid that non-schizophrenics, suggesting that they make more dopamine
  • Figee et al looked at the effect of antipsychotic drugs on the brain. The study showed enhanced activity in the prefrontal region of the brain of schizophrenics, confirming that the prefrontal cortex is important in causing schizophrenia
  • Strongly scientific and lab and animal studies show supporting evidence, such as Randrup & Munkvad's study

Disadvantages

  • PET scans show that blocking dopamine receptors does not always work
  • Blocking dopamine receptors takes a few days to work
  • Amphetamines produce only positive symptoms
  • Different types of dopamine receptor in different brain areas give different results
  • Glutamate may also be implicated
  • Social and environmental factors are also involved. This explanation is reductionist
  • Depatie & Lal found that apomorphine, a drug that increases the effect of dopamine, did not create any schizophrenic symptoms in their participants
  • It is hard to know whether excess dopamine causes schizophrenia, or if schizophrenia causes excess dopamine - cause and effect is not established

Evaluation

Overall, there is strong support for the Dopamine Hypothesis, and there does seem to be a definite link; however, cause and effect relationships have not yet been established and there are certainly environmental and psychosocial factors to be taken into account.

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