Biological explanations

• Genetics: Genes consist of DNA strands which make up 'instructions' for features. Genes are transmitted from parents to offspring.
• Neural correlates: Patterns of structure or activity in the brain that occur in conjunction with an experience and may be implicated in the origins of that experience.
• Dopamine: A neurotransmitter that generally has an excitatory effect and is linked to the sensation of pleasure. Unusually high levels are associated with schizophrenia, usually low levels are associated with Parkinson's disease.
• Family studies:

  • Confirmed risk of schizophrenia increases in line with genetic similarity to someone who already has the condition.
  • E.G. you have a 9% chance of getting it if you have a sibling with schizophrenia.
• Gottesman:

  • Completed a large scale study and found that someone with an aunt who has schizophrenia has a 2% chance of getting it as well.
  • There was a correlation found however this doesn't mean causation.
• Candidate genes:

  • Schizophrenia is polygenic meaning more than one gene is involved.
  • The most likely genes are those coding for neurotransmitters such as dopamine.
• Ripke et al:

  • Combined all previous data from genome wide studies.
  • He found that 108 separate genetic variations were linked to an increased risk of schizophrenia.
• Schizophrenia is aetiologically heterogeneous- different combinations of factors can lead to the condition.
• The role of mutation:

  • Schizophrenia can also have genetic origin in the absence of family history!
  • Mutation in parental DNA can be caused by radiation, poison or viral infection, this mutation can cause a risk of schizophrenia.
  • Evidence for mutation comes from a positive correlation between parental age and the risk, older parents are more likely to get the mutation (Brown et al).
• Neural correlates of schizophrenia:

  • The best known correlate is the neurotransmitter dopamine as it is important in the function of several brain systems related to the symptoms of schizophrenia.
• The original dopamine hypothesis:

  • Drugs used to treat schizophrenia caused symptoms similar to those with Parkinson's disease, therefore schizophrenia could be a result of high dopamine levels.
  • Excess DA in receptors to the Broca's area could help to explain speech poverty.
• Updated versions of the dopamine hypothesis:

  • Davis et al (1991): Added cortical hypodopaminergia which explains that low DA levels in the brains cortex can lead to schizophrenia.
  • This could also lead to subcortical hyperdopaminergia, so both high and low levels of DA can cause schizophrenia.
  • Also tries to explain origins of abnormal DA functions.
• Genetic research evaluation (Strength):

  • Research support: There is a strong evidence base!
  • Gottesman- Risk increases with genetic similarity.
  • Tienari et al- Biological children of parents with schizophrenia are at a heightened risk even if they grow up in an adoptive family so genetics must have an impact it cant just be the environment.
  • Hilker et al- Concordance rate of 33% for identical twins and 7% for not identical.
  • Proves some people are more at risk due to genetic make-up.
• Genetic research evaluation (limitation):

  • Environmental factors: There is clear evidence to show environmental factors also increase the risk of developing schizophrenia.
  • Genetic factors alone cannot provide a clear explanation.