Biological factors

• Types of biological factors

  • Genetic factors
  • Biochemical factors
  • Neurological factors
  • Evolutionary explanations
• Genetic factors

  • Genetically related to someone with schiz increase chance of developing schiz
• Genetic factors

  • Gottesman 40 twin studies found identical twins had 48% concordance with schiz
  • 17% concordance in non-identical twins
  • Significant as twins share same environment meaning increased concordance is genetic influence
• Strengths of Genetic factors

  • Shields found MZ twins in different families showed 50% concordance
  • Adoption studies founf children are adopted as one or more biological parent has SZ, genes more significant than environment
• Weaknesses of Genetic factors

  • No study found 100% concordance rate between MZ twins
  • Schiz not just explained by genes
  • Shared environment may cause higher concordance rates in family studies as children imitate schiz behaviours
• Biochemical factors

  Post-mortem and PET scans shown people with schiz have abnormally high levels of dopamine. Dopamine overactive in brains of people with schiz
• Evidence for biochemical factors

  • Antipsychotics reduce symptoms of schiz blocking dopamine receptors
  • Drugs like amphetamines sometimes cause schiz like symptoms in people without schiz
• Evidence against biochemical factors

  • Antipsychotics only work on positive symptoms of schiz meaning increased dopamine function doesn't explain negative symptoms
  • Link between dopamine is correlational
• Neurological factors

  • Neural correlates such as abnormal brain structure could explain schizophrenia
• Positives of neurological factors

  • Johnstone et al compared size of ventricles in brains of people with brains with and without schiz
  • People with schiz have enlarged ventricles
  • Schiz linked to reduction in temporal and frontal lobe volume
  • MRI scans on Schiz brains found abnormality in prefrontal cortex
• Weaknesses of neurological factors

  • People without schiz can also have enlarged ventricles
  • Findings are correlational
• Evolutionary explanation

  • Some explantions suggest there is an advantage having schiz
  • Some explanations say schiz share characteristics to shamans of the past
• Positives of evolutionary explanations

  • Strong genetic link to schizophrenia that there must be an evolutionary explanation
• Negatives of evolutionary explanations

  • Little evidence of theory and is difficult to prove