Biological explanations

• Biological explanations

  Assumption that schizophrenia is inherited.
• Family studies

  Gottesman found that someone with an aunt with schizophrenia has a 2% chance of developing it, increasing to 9% if the individual is a sibling and 48% if they are an identical twin.

  • Family members tend to share aspects of their environment as well as many of their genes, so correlation represents both.
• Candidate genes

  Schizophrenia is polygenic.

  • Likely genes are those coding for dopamine.
  • Ripke's genome study of 37000 with schizophrenia and 113000 neuro-typical individuals, and found 108 different genetic variations which were linked to increased susceptibility of developing schizophrenia.
• Role of mutation

  Mutation in parental DNA which can be caused by radiation, poison or viral infection.

  Evidences comes from positive correlation between paternal age and risk of schizophrenia, increasing from 0.7% with fathers under 25 to over 2% in fathers over 50.
• Dopamine hypothesis

  • Snyder found excessive amounts of dopamine in schizophrenic patients.
  • Phenothiazine s reduced schizophrenic behaviour by reducing dopamine.
  • L-dopa stimulates dopamine production and increases schizophrenic behaviour.
• Hyperdopaminergia in the subcortex sees high dopamine levels at the centre of the brain might be responsible for positive symptoms.
• hypodopaminergia in the cortex sees that high dopamine levels at the cortex might be responsible for negative symptoms.
• Brain structure

  = Actual mechanical working of the brain that is the issue.

  • Enlarged ventricles and trauma to frontal cortex as a cause of the illness.
  • Johnstone found that schizophrenic patients tended to have large ventricles and brain tissue loss.
  • Tilo found using fMRI on an ink blot test, found that patients with schizophrenia had less activity in Wernicke's area of the brain.
• Evaluation- research support

  • Family studies like Gottesman show that risk increases with genetic similarity to a family member with schizophrenia.
  • Adoption studies such as Tienari show that biological children of parents with schizophrenia are at a heightened risk even if they grow up in an adoptive family.
  • Twin study by Hilker showed a concordance rate of 33% for identical twins and 7% for non identical twins.
• Evaluation- environmental factors

  • Environmental factors increases the risk of developing schizophrenia
  • Biological risk factors include birth complications and smoking.
  • Psychological risk factors include childhood trauma which leaves people more vulnerable to schizophrenia.
  • 67% of people with schizophrenia reported at least one childhood trauma as opposed to 38% of a matched group with non-psychotic mental health issues.
  • So genetic factors cant provide a complete explanation
• Evaluation- evidence for dopamine

  • Amphetamines increase dopamine and worsen symptoms in people with schizophrenia and induced symptoms in people without.
  • Antipsychotic drugs reduced dopamine activity and also reduce intensity of symptoms.
  • Some candidate genes act on the production of dopamine or receptors.
  • Suggests dopamine is involved in symptoms of schizophrenia.
• Evaluation- glutamate

  Limitation of dopamine hypothesis is evidence for a central role of glutamate.

  • Post-mortem and live scanning studies have found raised levels of glutamate in several brain regions of people with schizophrenia.
  • Several candidate genes for schizophrenia are believed to be involved in glutamate production or processing.