evaluating dopamine hypothesis

• RELIABLE RESEARCH EVIDENCE

  several pieces of ev - link = high dopamine levels and +ve symptoms

  Griffiths et al (68) - administered volunteers with dop agonist (dextro-amphetamine) and observed - demonstrated abrupt onset of symptoms (paranoid delusions)

  link - increased dop levels and +ve symptoms

  f = reliable - consistently demonstrated in different research

  H - ev may not be conclusive proof of causation > identifies link only + doesn't account for other symptoms

  EXT - other R = no difference between SZ and non SZ for dopamine activity > inconclusive
• USEFUL APPLICATIONS

  AP (e.g. phenothiazine's) work by blocking dop rec + targets overactive dop neurons to lower dop levels

  } Cole et al (64) - controlled research

  > AP antagonist effectiveness > 75% given AP improved compared to 25% - placebo

  supports altering dop levels reduces symptoms > sug dop - implicated in causing symptoms

  Counter = AP use - not effective for 100% of patients and placebos > effective for some

  > sug - other factors responsible > dop - unlikely to be sole cause

  - doesn't work for everyone
• REDUCTIONIST

  exp - reduces cause of SZ (complex disorder) down to imbalances in brain chemistry and pathways

  SZ caused solely by brain chemistry = too simplistic

  other important explanations = ignored / overlooked

  Counter = reductionist - beneficial - by isolating dop as cause > treatments can be developed based on treating dop imbalance

  > opportunities for application
• INCONCLUSIVE EVIDENCE

  different R studies using B scans - produce contradictory findings + don't provide concrete evidence that dop imbalance causes SZ

  } Abi-Dargham et al (2000) - SPCET scans

  > found significant differences in D2 activity between 18 SZ and control

  H } Copolov + Crook (2000) - PET scans

  > no significant differences in dop activity in brains of SZ and non SZ

  inconsistencies in studies > question reliability of findings and their worth as valid evidence for explanation

  research - no differences in dop activity > question validity of whole exp
• INCONCLUSIVE EVIDENCE

  EXT - diff in DA - maybe - result of taking AP

  - diff in dop levels - maybe - varying levels of meds by patients in B scan study
• CONCLUSION

  • fails to explain why dopamine levels = dysfunctional
  • highly respected and widely accepted as explanation of SZ
  • ignores important factors: genes, env, childhood
  • useful application - drug treatment
  • better explanation - Diathesis Stress Model > biological pre-disposition and environmental trigger