Biological Explanations for Schizophrenia

• How does genetic similarity affect the risk of schizophrenia?

  Risk increases with genetic similarity
• What did Gottesman’s (1991) study investigate?

  Concordance rates of schizophrenia in twins
• What is the monozygotic twin concordance rate for schizophrenia?

  48%
• What is the dizygotic twin concordance rate for schizophrenia?

  17%
• What does it mean that schizophrenia is polygenic and aetiologically heterogeneous?

  It involves multiple genes and causes
• Which neurotransmitter genes are likely involved in schizophrenia?

  Genes coding for dopamine
• What did Ripke et al (2014) find in their study?

  108 genetic variations linked to schizophrenia
• How can mutations in parental DNA affect schizophrenia?

  They can lead to the disorder
• What is the correlation between paternal age and schizophrenia risk?

  Increases from 0.7% to 2% with age
• What does research support indicate about genetic factors in schizophrenia?

  • Risk increases with genetic similarity
  • Adoption studies show biological children at risk
  • Genetic makeup contributes to vulnerability
• What environmental factors influence the risk of developing schizophrenia?

  • Biological and psychological influences
  • Childhood trauma linked to higher risk
  • Genetic factors alone do not explain schizophrenia
• Why is dopamine important in schizophrenia?

  It affects brain systems related to symptoms
• What does the original dopamine hypothesis suggest?

  High dopamine levels cause schizophrenia
• What is hyperdopaminergia?

  High levels of dopamine
• How might excess dopamine receptors affect speech in schizophrenia?

  They may explain speech poverty
• What did Davis et al (1991) propose about dopamine levels?

  Low dopamine levels exist in the cortex
• What is hypodopaminergia?

  Low levels of dopamine
• How could low dopamine levels in the prefrontal cortex affect schizophrenia?

  They could explain negative symptoms
• What evidence supports the role of dopamine in schizophrenia?

  • Amphetamines worsen symptoms by increasing dopamine
  • Antipsychotic drugs reduce dopamine and symptoms
  • Candidate genes affect dopamine production
• What have studies found about glutamate levels in schizophrenia?

  Raised levels found in several brain regions
• What is suggested about candidate genes in relation to glutamate?

  They may be involved in glutamate processing
• What neurotransmitters are implicated in schizophrenia?

  • Dopamine: high and low levels affect symptoms
  • Glutamate: raised levels linked to the disorder
  • Other neurotransmitters may also play a role
• What is a strength for Genetics as a cause of Schizophrenia?

  Research Support

  • Family studies such as Gottesman (1991) show that risk increases with genetic similarity to a family member with schizophrenia
  • Adoption studies show that the biological children of parents with schizophrenia are at a heightened risk even if they grow up in an adoptive family
  • This shows that some people are more vulnerable to schizophrenia as a result of their genetic makeup
• What is a limitation for Genetics as a cause of Schizophrenia?

  Environmental Factors

  • Environmental factors include both biological and psychological influences, and there is clear evidence to suggest that they increase the risk of developing schizophrenia
  •  Mørkved et al (2017) found that 67% of people with schizophrenia and related psychotic disorders reported at least one childhood trauma as opposed to 38% of a matched group with non-psychotic mental health issues
  • This means that genetic factors alone can not provide a complete explanation for schizophrenia
• What is a limitation for the Dopamine Hypothesis as a cause of Schizophrenia?

  Glutamate

  • Post-mortem and live scanning studies have consistently found raised levels of glutamate in several brain regions of people with schizophrenia
  • In addition, several candidate genes for schizophrenia are believed to be involved in glutamate production or processing
  • This means that an equally strong case can be made for a role of other neurotransmitters
• What is a strength for the Dopamine Hypothesis as a cause of Schizophrenia?

  Evidence for Dopamine

  • Amphetamines increase dopamine levels and worsen symptoms in people with schizophrenia and induce symptoms in people without
  • Additionally, antipsychotic drugs reduce dopamine levels and also reduce the intensity of symptoms, as well as candidate genes acting on the production of dopamine
  • This strongly suggests that dopamine is involved in the symptoms of schizophrenia