Biological Explanations

• There are two main biological explanations for schizophrenia
• Biological explanations for schizophrenia

  • Genetics
  • Neural correlates: The dopamine hypothesis
• Genetics


  The genetic basis of schizophrenia has been investigated using family studies and studies of individual genes
• Family studies


  • Schizophrenia is more common among the biological relatives of an individual with schizophrenia, and the greater the degree of genetic relatedness, the greater the risk
  • Individuals with an identical twin who suffers from schizophrenia have a 48% risk of being diagnosed with the disorder
  • Individuals with a sibling who suffers from schizophrenia have a 9% risk of being diagnosed with the disorder
  • The general risk of being diagnosed with the disorder is just 1%
• Candidate genes


  Genes that have been related to schizophrenia
• Schizophrenia is polygenic, meaning it is unlikely to be related to a single gene
• Schizophrenia is aetiologically heterogeneous, meaning different combinations of genes can lead to the condition
• Ripke et al. (2014) found that 108 separate genetic variations were associated with an increased risk of schizophrenia
• Neural correlates


  Specific abnormalities within the brain that have been associated with the development of schizophrenia
• Dopamine hypothesis


  • Dopamine is one of the neurotransmitters involved in schizophrenia
  • The original version focused on high levels of dopamine activity (hyperdopaminergia) in the subcortex and positive symptoms
  • More recent versions have also focused on low levels of dopamine activity (hypodopaminergia) in the cortex and negative symptoms