biological explanation

• what are the 3 main assumptions of the biological explanation to schizophrenia?

  1. genetics
  2. neural correlations
  3. dopamine hypothesis
• outline the role of genetics in explaining schizophrenia

  schizophrenia runs in families

  
  

  polygenic with different genes contributing to increased risk

  • Ripke et al: 108 variations

  aetiologically heterogeneous as different combinations of genes are implicated in the disorder
• who investigated the role of genetics in schizophrenia?

  Gottesman in 1991
• what did Gottesman find about the genetic basis of schizophrenia?

  closer the genetic relationship, higher the risk

  • general population = 1% risk
  • sibling = 9% risk
  • MZ twin = 48% risk

  more genes the person shares with the sufferer, more likely to develop disorder
• strength of genetic explanation - evidence

  • family & twin studies
  • Gottesman found risk of schizophrenia is higher amongst individuals with close family members who have the disorder
  • clear genetic predisposition
• what is dopamine?

  neurotransmitter associated with schizophrenia symptoms
• what are the 2 parts to the dopamine hypothesis?

  1. hyperdopaminergia
  2. hypodopaminergia
• explain hyperdopaminergia

  excess dopamine in subcortex

  • overactivity in broca's area explains hallucinations and disorganised speech
• explain hypodopaminergia

  low dopamine in prefrontal cortex

  • linked to negative symptoms
• strength of the dopamine hypothesis- support

  • Curran et al found drugs increase dopamine activity that induce symptoms
  • strengthens validity
  • strong empirical support for neurotransmitter imbalances
• what do neural correlations suggest?

  structure or functioning of the brain is correlated with positive and negative symptoms
• link enlarged ventricles to schizophrenia

  associated with negative symptoms

  • Johnstone et al - larger ventricles in schizophrenics
• link reduced prefrontal activity to schizophrenia

  associated with impaired decision-making and negative symptoms
• link temporal lobe abnormalities to schizophrenia

  Allen et al - reduced activity in superior temporal gyrus linked to auditory hallucinations
• strength of neural correlates - brain imaging

  • Allen et al found auditory hallucinations are linked to reduced activity in brain regions associated with speech processing
  • abnormalities in structure and function contribute to symptoms
  • supports neurological basis
• weakness of genetic explanation - complex

  • polygenic nature
  • doesn't provide direct cause-and-effect relationships
  • lacks explanatory power
• weakness of genetic explanation - incomplete

  • ignores environmental factors
  • e.g. trauma, stress or cannabis use
  • incomplete explanation
• weakness of dopamine hypothesis - simplistic

  • Javitt found glutamate and serotonin play a role
  • biological mechanisms are more complex
  • lacks explanatory power
• weakness of dopamine hypothesis - explanatory power

  • causation vs correlation
  • dopamine imbalances could be a secondary effect rather than root cause
  • limits explanatory power
• weakness of neural correlates - incomplete

  • causation vs correlation
  • brain abnormalities could be a byproduct of disorder rather than direct cause
  • lack explanatory power
• weakness of neural correlates - limited

  • Tilo et al found some individuals with schizophrenia don't exhibit abnormalities
  • genetic and environmental influences also play a role
  • incomplete explanation