Biological Explanations for Schizphrenia

• What is the genetic basis of schizophrenia?

  It involves an increased risk of the disorder with genetic similarity to relatives.
• What do family studies reveal about schizophrenia?

  • Risk increases with genetic similarity to relatives.
  • Gottesman's (1991) study shows a correlation between genetic similarity and probability of sharing schizophrenia.
• How does Gottesman's (1991) family study contribute to our understanding of schizophrenia?

  It demonstrates that as genetic similarity increases, so does the probability of sharing schizophrenia.
• Why is it important to consider both genes and environment in family studies of schizophrenia?

  Because family members share both environment and genes, which can influence the correlation.
• What does an increase in genetic similarity to relatives indicate about schizophrenia risk?

  It indicates an increased probability of developing the disorder.
• The three subtopics for the genetic basis of schizophrenia are family studies, candidate genes and the role of mutation
• Family studies

  Confirmed that the rusk of schizophrenia increases with genetic similarity to the relative with that disorder
• Large-scale family study

  Gottesman (1991) large-scale family study - as genetic similarity increases so does the probability of sharing schizophrenia
• Family members share environment as well as genes so the correlation represents both - family studies still give good support for the importance of genes in schizophrenia.
• Candidate Genes


  The next logical step is to identify these - early research looked for a single genetic variation - believed one faulty gene would explain schizophrenia.
• Candidate Genes


  the most likely genes would be those coding for neurotransmitters including dopamine.
• Candidate Genes

  Different studies have identified different candidate genes - it appears schizophrenia is aetiologically heterogeneours - meaning a different combination of factors can lead to the condition.
• The Role of Mutation

  Schizophrenia can have a genetic cause even if there’s no family history of it.
• The Role of Mutation

  Can be caused due to mutations in parental DNA - might be caused by radiation, poison or viral infections.
• The Role of Mutation

  Evidence shows (Brown et al. 2002) as fathers get older the risk of these mutations increases - from 0.7% in fathers under 25 to over 2% in fathers over 50.
• Neural correlates of schizophrenia

  Unaware what causes symptoms of schizphrenia on a biological level but research has identified some neural correlates - best known neural correlate is the neurotransmitter dopamine.
• The original dopamine hypothesis

  was based on drugs used to treat schizophrenia caused symptoms similar to Parkinson’s disease - schizophrenia is possibly due to high dopamine levels in sub or typical area of the brain.
• The original dopamine hypothesis

  An excess of da receptors in the pathways to brocades area may explain specific symtpoms of schizophrenia like hallucinations
• Updated version of dopamine hypothesis

  Kenneth Davis et al. (1991) proposed the addition of cortical hypodopaminergia - low dopamine levels in prefrontal cortex could explain cognitive problems.
• Updated version of dopamine hypothesis

  It has also been suggested that cortical hypodopaminergia leads to subcortical hypodopaminergia.
• Updated version of dopamine hypothesis

  Genetic variations and early stress experiences lead to increased sensitivity to cortical hypodopaminergia and subcortical hypodopaminergia.