biological explanation of schizophrenia

• cause of schizophrenia biologically?

  due to differences in biological structures within body such as genes/neurochemistry/brain structure
• what is the aetiology of schizophrenia?

  has a physical basis
• what did gottesman find?

  • rate of sz in general population is 1%
  • one parent - 12% likelihood child develops sz
  • both parents - 40%
• what are candidate genes?

  • specific genes which means people are more likely to suffer from sz
  • genes associated with increased risk of sz code for functioning of dopamine
• schizophrenia & candidate genes?

  • sz is polygenic - more than one gene associated with development of sz
  • sz is aetiologically heterogenous - several different combinations of genes can lead to sz & combinations vary between people
• ripke et al 2014?

  108 genetic variations associated with sz
• gurling et al?

  discovered mutations of PCM-1 gene responsible for 15% cases of sz
• define concordance rates?

  probability that pair of individuals will both have certain characteristic given that one of the pair has the characteristic
• concordance rates for sz?

  mz twins - 48%

  dz twins - 17%
• 2 * for genetic explanation?

  1. evidence to support from gottesman
  2. evidence to support from tienari
• * evidence to support from gottesman - genetic?

  • reviewed 40 twin studies & found 48% concordance rate for mz twins
  • 17% concordance rates for dz twins
  • as mz twins share 100% genes & dz share 50% findings suggest genetics influence sz
  • those genetically similar more likely to have sz compared to those less genetically similar
  • shows that higher amount of genes shared increased biological risk factor of developing sz
  • adds to nature argument - physical basis
• X concordance rates not 100%?

  as do not match exact amount of genes must be other environmental factors such as family dysfunction that could play a role
• * evidence to support from tienari 2004 - genetic?

  • if child whose biological mother has sz was adopted there was 10% higher chance they would develop disorder
  • compared to those adoptees whos biological mother didnt have sz
  • having parent with sz increases likelihood that individual will develop sz by inheriting their genes
  • shows genetics do play role in development of sz
  • when you have biological parent with sz chances of having disorder increase
  • support nature argument - bio factors more important than environmental causes
• neural correlate - dopamine hypothesis?

  dopamine is neurotransmitter linked to number of symptoms of sz

  1. hyperdopaminergia
  2. hypodopaminergia
• hyperdopaminergia in subcortex?

  • high levels of dopamine
  • excess of dopamine receptors in brocas area linked to positive symptom of auditory hallucinations
• link hyperdopaminergia to auditory hallucinations?

  • likely to hear voices as theres too much dopamine in brocas area - responsible for speech production
  • surplus of excitatory neurotransmitter which is positively charged
  • this means it fires too many messages causing you to hear things that are not actually there
• hypodopaminergia in pre frontal cortex?

  • low levels of dopamine
  • pre frontal cortex linked with thinking & decision making which causes negative symptoms
• link hypodopaminergia to avolition?

  if there is too little activity in areas responsible for decision making can lead to avolition - not deciding to to meet tasks/goals
• * evidence to support from curran 2004 - neural explanation?

  • found that people who take amphetamines have increase in sz symptoms & increases level of dopamine in brain
  • antipsychotic drugs work by reducing dopamine decreases symptoms of sz
  • shows high levels of dopamine linked to causing sz in particular + symptoms
  • shows dopamine must be involved in cause of symptoms due to excitatory nature positively charged nt & symptoms which add to individuals usual functioning
• X not everyone responds to drugs - neural?

  • research shows typical antipsychotic drugs that work by reducing dopamine only benefits 65% of people
  • population validity
  • if increased levels of dopamine were only cause of sz treatment should work for 100%
  • may be other explanations & not just due to imbalance of excitatory nt
  • not everyone experiences same + symptoms
  • difficult to generalise concept to all individuals with sz
• 3 neural correlates?

  1. enlarged ventricles
  2. ventral striatum
  3. superior temporal gyrus
• what is a neural correlate?

  when structure/function of brain correlates with development of sz
• enlarged ventricles?

  fluid filled gaps in brain

  leads to damage to central brain areas & pre frontal cortex

  BOTH POSITIVE AND NEGATIVE SYMPTOMS LINKED
• ventral striatum?

  low levels of activity correlates with avolition & other negative symptoms
• superior temporal gyrus?

  low levels of activity correlates with auditory hallucinations
• 2 X of biological explanation?

  1. issues determining cause & effect
  2. reductionist
• X issues with determining cause & effect?

  • not clear whether changes to brain activity causes sz
  • or whether brain changes occur as a result of getting disorder
  • cant be concluded whether its enlarged ventricles that cause symptoms of sz/if symptoms of sz cause enlarged ventricles
  • may be 3rd intervening variable - upbringing/family dysfunction that causes both changes to brain activity & symptoms of sz
  • internal
  • cannot establish cause & effect between brain ventricle size & sz or whether other variables also have an effect
• X reductionist?

  • bio exp - caused by genetics,high/low levels of dopamine & changes to brain activity
  • fails to recognise importance of environmental factors - upbringing
  • diathesis stress model better exp - biological vulnerability to sz & stress trigger are necessary to develop sz
  • other factors play role in sz
  • more appropriate to use interactionist approach that people may be biologically predisposed to sz but its not there until theres an adverse environmental trigger that sz symptoms manifest
  • its interaction of nature & nurture rather than just product of our innate genetic pre disposition