Biological explanations for schizophrenia

• What are the two biological explanations for schizophrenia?

  • Genetic
  • Neural
• how does schizophrenia run in families through genes?

  • heredity
  • Risk of developing disorder with schizophrenic family members is higher than for those who don’t have schizophrenic relatives
  • Different combinations of genes make individuals more vulnerable to schizophrenia
• does having the genes for schizophrenia mean that an individual will inevitably develop schizophrenia?

  • No
  • Diathesis stress- environmental stressor might need to be contributed
• what did Gottesman find in his study?

  • children with two schizophrenic parents- concordance rate 46%
  • Children with one schizophrenic parent- concordance rate 13%
  • children with schizophrenic siblings- concordance rate 9%
• What were the findings of Joseph’s twin studies? What could we conclude from this?

  • concordance of DZ twins 7.4%
  • Concordance rate of MZ twins 40.4%
  • proves there is greater similarities due to genetic factors
• How can you analyse concordance effectively?

  • rear twins apart from each other
  • Blind twin studies where the researcher doesn’t know the twin they are assessing is MZ or DZ
• What is meant by the term neural correlates?

  Changes in neuronal mechanisms resulting in the characteristic symptoms of schizmophrenia
• how do different areas of the brain provide evidence for schizophrenia?

  • hippocampus- anatomical changes in the hippocampus of schizophrenic patients- Gotto and Grace- showed hippocampus dysfunction can influence levels of dopamine release
  • pre-frontal cortex- impaired in schizophrenic patients
  • grey matter- schizophrenic patients have a reduced volume of grey matter.
  • those displaying negative symptoms have enlarged ventricles- consequence of nearby parts not developing properly
  • white matter- reduced mylenation of white matter in schizophrenic patients
• AO3 for neural correlates?

  • 😊support for impact of grey matter deficits- Vita et al- patients with schizophrenia showed a higher reduction in cortical grey matter
  • 😊implications for treatment- Addington et al- use of neuroimaging to predict those who will develop psychoses for earlier treatment
• What are adoption studies?

  Studies of genetically related individuals who have been reared apart
• why are adoption studies useful in biological explanations? describe an example of an adoption study

  • adoption studies are used to study genetically related individuals reared apart, in order to distinguish between genetic and environmental influences
  • Tienari et al- 164 adoptees whose bio mother was diagnosed with schizophrenia
  • 6.7% also schizophrenic
  • compared to only 2% of 197 control adoptees who were born to non schizophrenic mothers
  • genetic liability to schizophrenia confirmed
• describe what is meant by the dopamine hypothesis and explain the key ideas of the theory?

  • An excess of the neurotransmitter dopamine in certain brain regions is associated with positive symptoms of schizophrenia
  • neurones fire too easily or too often
  • Lead to hallucinations and delusions
  • abnormally high numbers of D2 receptors on receiving neurones, so more dopamine binds and more neurones fire
• state evidence for the dopamine hypothesis concerning drugs that increase dopamine activity

  • amphetamine- dopamine agonist, stimulates nerve cells containing dopamine, causing the synapse to be flooded with dopamine
  • normal people who recieve large doses of amphetamine can develop characteristic delusions and hallucinations of schizophrenics
  • People suffering from parkinsons disease take the drug to raise dopamine levels and have been found to have schizophrenic type symptoms (Grilly)
• State evidence for the dopamine hypothesis for drugs that decrease dapaminergic activity

  • Antipsychotic drugs
  • Block the activity of dopamine in the brain
  • Reduces activity in the neural pathways of the brain that use dopamine
  • Consequently these drugs eliminate hallucinations and delusions
  • These drugs are known as dopamine antagonists as they block the action of dopamine
  • Supports the role of dopamine in schizophrenia as the drugs used to reduce dopamine alleviates symptoms
• what is the main principle of the revised dopamine hypothesis?

  • Davis and Khan proposed the positive symptoms of schizophrenia are caused by an EXCESS of dopamine in subcortical areas of the brain, particularly the mesolimbic pathway
  • Negative and cognitive symptoms thought to arise from a DEFICIT of dopamime in areas of the prefrontal cortex
• two pieces of evidence to support the revised dopamine hypothesis?

  • neural imaging- Patel et Al used PET scans to assess dopamine levels, they were lower in the prefrontal cortex of schizophrenic patients compared to controls
  • Animal studies- wang and deutch- induced dopamine depletion on the prefrontal cortex in rats, resulted in cognitive impairment which could be reversed using antipsychotics, thought to have a beneficial effect on negative symptoms
• evaluate genetic explanations for schizophrenia

  • ☹️ rearing patterns may explain why schiz runs in families, instead of heredity- research on expressed emotion shows successive negative emotional climates in families can lead to stress, triggering a schizophrenic episode
  • ☹️ MZ twins encounter more similar environments-research shows that greater concordance between MZ twins is a result of greater genetic similarity, but Joseph argues that MZ twins have a more similar environment that DZ twins, (eg- MZ= same sex) so treated more equally, differences in concordance between MZ and DZ twins may be therefore due to environment
• evaluation of the dopamine hypothesis? (neural correlates)

  • 😊evidence from treatment- antipsychotic drugs- alleviate schizophrenic symptoms. leutch et Al conducted meta analysis of 212 studies and found antipsychotics are significantly more effective compared to placebo
  • ☹️Challenges to dopamine hypothesis- Noll claims that antipsychotic drugs don’t alleviate symptoms in about 1/3 of people, symptoms persist despite dopamine levels being normal, blocking D2 receptors dont do anything, so must be other neurotransmitter systems responsible for schizophrenia