Biological Explanations for Schizophrenia

• What is one biological explanation for schizophrenia (SZ)?

  It is passed on through genes.
• What does it mean that schizophrenia (SZ) is polygenic?

  A number of genes have been implicated in its development.
• What does it mean that SZ is aetiologically heterogenous?

  Different studies have identified different candidate genes.
• How many genetic variations did Ripke et al find associated with increased risk of SZ?

  108 separate genetic variations.
• What have family studies established about the occurrence of SZ?

  SZ is more common among biological relatives of a person with SZ.
• What is the concordance rate for children with two schizophrenic parents according to Gottesman and Shields?

  46%
• What is the concordance rate for siblings of individuals with SZ?

  9%
• What is the chance of developing SZ if an identical twin of one parent has SZ?

  17% chance.
• What does the family study data suggest about the influence of genes over nurture?

  It shows a significant influence of genes.
• What does it suggest if MZ twins are more concordant than DZ twins?

  It suggests that greater similarity is due to genetic factors.
• What were the concordance rates found by Gottesman and Shields for MZ and DZ twins?

  42% for MZ twins and 9% for DZ twins.
• Why is the concordance rate for MZ twins not 100%?

  It suggests that other factors must also be involved.
• What is one explanation for why two-thirds of people with SZ have no relatives with a similar diagnosis?

  It may be due to mutations in parental DNA.
• What is the purpose of adoption studies in the context of SZ?

  To disentangle genetic and environmental influences.
• What percentage of adoptees whose biological mothers had SZ received a diagnosis of SZ according to Tienari et al?

  1. 7%
• What did Tienari et al conclude from their findings?

  That the genetic liability to SZ had been decisively confirmed.
• What assumption is made in all twin studies regarding MZ and DZ twins?

  That their environments are equivalent.
• What does Joseph argue about the treatment of MZ and DZ twins?

  MZ twins are treated more similarly than DZ twins.
• What does Joseph suggest about the differences in concordance rates between MZ and DZ twins?

  They reflect environmental differences rather than genetic differences.
• What does the fact that concordance rates are not 100% imply about SZ?

  It cannot be a wholly genetic disorder.
• What does the predisposition theory suggest about SZ?

  Genes alone do not cause SZ but predispose individuals to it.
• What is a limitation of focusing solely on biological factors in explaining SZ?

  It ignores the role of psychological factors.
• What does research on twins with identical genes show about concordance rates?

  They are far from 100%.
• What is likely to explain why one twin develops SZ and the other does not?

  Psychological factors rather than biological ones.
• What is the definition of neural correlates?

  Patterns of cortical activity or neural structures that coincide with specific psychological symptoms.
• What does the original dopamine hypothesis suggest?

  Hyperdopaminergia in the subcortex is responsible for SZ.
• What does the modern understanding of the dopamine hypothesis suggest?

  Both hyper- and hypodopaminergia in different brain areas contribute to SZ.
• What is hyperdopaminergia associated with?

  Positive symptoms of SZ.
• Where is hyperdopaminergia specifically noted to occur?

  In the frontal lobe, particularly Broca's area.
• What symptoms may result from hyperdopaminergia in Broca's area?

  Auditory hallucinations.
• What is hypodopaminergia associated with?

  Negative symptoms of SZ.
• Where did Rakic et al suggest hypodopaminergia occurs?

  In the prefrontal cortex.
• What negative symptoms may result from hypodopaminergia in the prefrontal cortex?

  Speech poverty and avolition.
• What are the implications of the dopamine hypothesis for drug treatments?

  It informs the development of antipsychotics/dopamine antagonists.
• What is the role of the ventral striatum?

  It evaluates reward values, predictability, and risks.
• What did Juckel et al suggest about the ventral striatum?

  Low activation levels may be associated with avolition.
• What did Allen et al conclude about the anterior cingulate and left temporal cortex?

  They are associated with functional abnormalities in auditory verbal hallucinations.
• What was the method used by Allen et al in their study?

  fMRI to record brain activity during auditory hallucinations.
• What does supporting evidence for the dopamine hypothesis come from?

  The success of drug treatments that alter dopamine activity.
• What is the basic mechanism of antipsychotic drugs?

  To reduce the effects of dopamine.