Biological Explanation of Schizophrenia

• What are genes?


  Genes are sections of DNA that control production of a particular protein
• What does the genetic explanation say about schizophrenia?


  • There are multiple gene alleles that increase the risk of developing schizophrenia.
  • If members of our family have schizophrenia, we are more likely to develop schizophrenia.
  • The more genetic risk alleles a person has, the more likely they are to develop schizophrenia.
• Gottesman & Shields twin study on schizophrenia found that there was a 74% concordance rate in monozygotic twins, and a 24% concordance rate in dizygotic twins. This indicates schizophrenia is partially influenced by our genetics and partially by environment.
• Which of the following are limitations of adoption studies?


  They assume that any similarity between biological parent and adopted child is solely down to genetics.

  They ignore similarities in environments shared between adopted children and their biological parents.
• What is the name of the researchers who conducted a twin study, to investigate the genetic explanation of schizophrenia?

  Grottesman and Shields

  Concordance rate MZ (74%) and DZ (24%)
• What are the 2 hypothesis for brain abnormalities that cause schizophrenia?

  1. Neural correlates
  2. Dopamine Hypothesis
• What does the neural correlates explanation of schizophrenia say the disorder is caused by?


  abnormal brain structure
• What characteristics are present in the brains of those with schizophrenia?

  Larger ventricles

  Smaller Front Cortex
• Torreys brain imaging study


  Torrey conducted MRI scans on people with schizophrenia, comparing scans between people with schizophrenia and people with healthy brains. He found that people with schizophrenia had 15% larger ventricles than those in the control group. The study supports the neural correlates explanation of schizophrenia.
• What is a limitation of the neural correlates hypothesis?


  We don’t have sufficient evidence to conclude that brain abnormalities cause schizophrenia, because the evidence obtained from MRI studies are correlational. The drug medication that patients take to treat schizophrenia may act as a confounding variable in studies of neural correlates.
• What happens when more excitatory neurotransmitters bind to post-synaptic receptors?


  More positively charged particles flow into the post-synaptic neuron.
• What does dopamine do?

  Dopamine is involved in processing reward and in controlling attention.
• The dopamine hypothesis says that people with schizophrenia have more dopamine than normal in the mesolimbic system.
• What does the revised dopamine hypothesis state?


  • People with schizophrenia have high levels of dopamine in the mesolimbic pathway.
  • Overactivity in the mesolimbic system causes the positive symptoms of schizophrenia.
  • People with schizophrenia have lower levels of dopamine in the frontal cortex than usual.
  • Underactivity in the frontal cortex causes negative symptoms
• The dopamine hypothesis: Study Support 


  Drug studies:

  • Drugs that decrease dopamine decrease positive symptoms of those with schizophrenia
• Limitations of the dopamine hypothesis: Noll's study


  Noll's study reviewed people with schizophrenia that were given drugs that reduce dopamine levels and monitored the positive symptoms they experienced. He found that high levels of dopamine are not the only case of positive symptoms (only 2/3 symptoms were reduced) demonstrating a limitation of the dopamine hypothesis.
• What is the name of the drug that increases dopamine levels, leading to the experience of hallucinations and delusions in otherwise healthy people?

  amphetamine 
• Limitations of the Dopamine Hypothesis: Montcrieff's review

  • Drugs that increase dopamine, like amphetamine, also increase the levels of other neurotransmitters, so we can’t be sure that it’s the increased dopamine that is causing these symptoms.
  • Some post-mortem studies reported increased levels of dopamine in the mesolimbic pathway, but other studies reported no difference compared to the control brains.
• Biological explanation of schizophrenia 


  People with schizophrenia carry alleles that increase the risk of developing schizophrenia. - Genetic explanation

  Schizophrenia is caused by an abnormal brain structure - Neural correlates hypothesis.

  People who have schizophrenia experience an imbalance of neurotransmitters in the brain - Dopamine hypothesis
• What is the biological treatment for schizophrenia?


  Antipsychotics - reducing dopamine levels
• How do antipsychotic drugs work?


  • Antipsychotics prevent dopamine from binding to post-synaptic receptors.
  • Antipsychotics reduce the overactivity of neurons in the mesolimbic pathway.
• What is the mesolimbic system?


  The group of brain regions involved in processing reward.
• What are the limitations of traditional antipsychotics?


  • Antipsychotic drugs can cause side effects in patients with schizophrenia.
  • Antipsychotic drugs can cause extra-pyramidal symptoms.
• What is a limitation of antipsychotic drugs: not side-effects?


  They are unable to treat negative symptoms
• What side effects are common in people who take antipsychotics?


  • Modility issues
  • Diabetes
  • Obesity
  • Cardiac Issues
• Explain why antipsychotic drugs both are unable to treat negative symptoms, and potentially make them worse.


  Antipsychotics reduce the dopamine activity levels in all areas of the brain. Negative symptoms of schizophrenia are thought to be caused by reduced dopamine levels in the frontal cortex. So antipsychotics not only lack the ability to treat these symptoms, but could make them more intense, because they further reduce dopamine activity levels in the frontal cortex.
• Atypical and typical antipsychotics 


  • Typical antipsychotics bind to dopamine receptors in order to block dopamine.
  • Atypical antipsychotics bind to dopamine receptors in order to block dopamine.
  • Atypical antipsychotics are able to treat negative symptoms when typical antipsychotics are not.
• Leucht (2001) meta-analysis (65 studies) looking at the effectiveness of antipsychotic drugs. He found that antipsychotic drugs were more effective than placebos and led to lower relapse rates
• Why do atypical antipsychotics lead to fewer side effects?


  Atypical antipsychotics bind to dopamine receptors for shorter periods of time.
• Comparing the effects of Atypical and typical antipsychotics


  Crossley (2010) meta analysis (15 studies) he found there was no significant difference between how effective they were at preventing the symptoms but found they had significantly fewer side effects than typical antipsychotics.
• What is a limitation of both typical and atypical antipsychotics?


  • Patients who stop taking either drug are likely to experience relapse.
  • Not treating the underlying cause, just covering the symptoms