Biological explanations for schizophrenia

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  • Biological explanations for schizophrenia:
  • AO1:
  • Genetic basis - schizophrenia runs in families:
  • Strong relationship between genetic similarity of family members and likelihood of both developing schizophrenia. Gottesman's family study found MZ twins have a 48% shared risk of schizophrenia. DZ twins have a 17% shared risk and siblings (about 50% genes shared) have a 9% shared risk. 
  • Schizophrenia is polygenetic and aetiologically heterogeneous:
  • Existence of different candidate genes incicates the following:
  • Each individual gene confers a small increased risk of schizophrenia (it is polygenetic)
  • Different combinations can lead to schizophrenia (it is aetiologically heterogeneous).
  • Ripke et al studied 37,000 patients and found 108 separate genetic variations associated with increaseed risk; many coded for the dopamine neurotransmitter. 
  • Dopamine hypotheis - Role of dopamine:
  • Dopamine (DA) is widely believed to be involved in schizophrenia because it is featured in the functioning of brain systems related to the symptoms of schizophrenia. High dopamine activity in subcortex (central areas of the brain) associated with hallucinations and poverty of speech (e.g. excess of dopamine receptors in Broca's area).
  • More recent versions of the hypothesis have focused on low levels of dopamine in the prefrontal cortex (responsible for thinking and decision-making).
  • Neural correlates:
  • Brain activity linked with symptoms:
  • Neural correlates are measurements of the structure or function of the brain that correlate with the positive or negative symptoms of schizophrenia. 
  • Avolition and ventral striatum:
  • Ventral stiatum is onvolved in anticipation of reward (related to motivation…

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