biological explanations of schizophrenia

• genetic basis of schizophrenia:

  • family studies (Gottesman) - MZ 48%, DZ 17%
• adoption studies:

  • tienari et al - 164 adoptees with schizo mother, 6.7% received diagnosis compared to 2% of control group
  • those with biological schizo mother 3x more likely to have same diagnosis
• candidate gene:

  • early research = one schizogene, now appears theres a combo that makes people vulnerable
  • different candidate genes = aetiologically heterogenous, genes are more likely to code for neurotransmitters e.g dopamine
• ripke et al: genome wide study

  • compared genetic makeup of 37000 patients to 113000
  • 108 separate variations associated with increased risk
• role of mutation: genetic origin in absence of family history

  • mutation of parental gene caused by radiation, poison, infections
  • brown et al - positive correlation between parental age + increased risk of sperm mutation (0.7% in fathers >25, 2% in fathers >50)
• neural explanations (original dopamine hypothesis):

  • based on antipsychotics (lower dopamine) caused parkinsonian symptoms
  • result of higher levels of dopamine in subcortical areas of brain
  • excess of dopamine receptors from subcortex to brocas area may explain symptoms e.g alogia + auditory hallucinations
• updated dopamine hypothesis (daus et al):

  • hypodopaminergia - low levels in prefrontal cortex, explains cognitive symptoms e.g negative symptoms
  • cortical hypodopaminergia leads to subcortical hyperdopaminergia
• EVALUATION: genetics research support

  • Gottesman, 48% MZ, 17% DZ
  • adoption studies - influence of genetics in absence of environmental influences
  • overwhelming evidence, higher validity
• EVALUATION: neural research support - drug treatments

  • leucht et al - 212 study metaanalysis - antipsychotics more effective than placebos
  • all drugs more effective in treatment of negative + positive symptoms
  • supports hypothesis, dopamine plays role in development
• EVALUATION: biological reductionism

  • concordance rates - MZ isnt 100%, other factors involved
  • Noll et al - evidence against antipsychotics, dont alleviate delusions/hallucinations in 1/3 of patients
  • explanations arent straight forward, holistic approach more appropriate