biological explanations

• genetic basis: schizo runs in families

  this is weak evidence as families share environment and genes, but systematic investigations eg, Gottman's large scale family study found identical twins had a 48% risk of developing schizo, siblings 9%.
• genetic basis: candidate genes

  individual genes believed to increase the risk of developing schizo.

  polygenic- schizo needs number of factors to work together

  aetiologically heterogenous- different combinations of factors

  investigated by Ripke combining previous data from genome wide studies and found 108 separate genetic variations = increased risk of schizo, all coding for neurotransmitters dA
• dopamine hypothesis- hyperdopaminergia


  hyperdopaminergia is high levels of DA receptors in the subcortex, brocas area, results in speech poverty, a negative symptom
• dopamine hypothesis- hypodopaminergia


  hypodopamingeria is low levels of DA in the prefrontal cortex which causes negative symptoms
• neural correlates


  measurements of the structure or function of the brain that correlate with an experience,

  negative: abnormalities in the ventral striatum cause avolition, as the VS involved with anticipation of rewards.

  positive: Allen scanned brains with hallunications and compared with control group, asked to identify pre-recorded speech. more erros in hallunication group and lower activity levels in the superior temporal gyrus + anterior cingulate gyrus.
• A03: multiple sources of genetic susceptibility

  evidence shows it is very important,

  Gottesman- genetic similarities give increased risk

  adoption studies- Pekka, children of schizo suffers at hightened risk despite being adopted,

  molecular level studies- showing particular genetic variations
• A03: mixed evidence for DA hypothesis


  supporting evidence- DA agonists increase the levels of DA can cause schizo symptoms in non sufferers and make symptoms worse. AND antipsychotic drugs, lower levels of DA

  Lindstrom- chemicals needed to produce DA taken up faster in schizo sufferers.

  against: Ripke said other neurotransmitters are coded for by the genes not just DA also glutamate.

  evidence mixed.
• A03: correlation causation issue

  due to corrlation cant determine the cause, could be third factor, symptom causes abnormality or abnormality causes symptom.