Biological Explanation

• inheritance

  • schizophrenia runs in families and there is a strong correlation between genetic similarity and risk of developing the condition
  • it is believed that risk is therefore passed down via genetic transmission (biological inheritance)
  • there is a strong relationship between the degree of genetic similarity and shared risk of SCZ
• candidate genes

  • a number of genes give a small increased risk of SCZ, therefore, SCZ is polygenic
  • Ripke et al (2014) identified 108 gens
  • SCZ is aetiologically heterogeneous - has different combinations of factors that can lead to the condition
  • Sekar et al (2016) - CC4 gene associated with higher SCZ risk
• the dopamine hypothesis

  • SCZ is the result of abnormal activity in dopamine pathways
  • mesolimbic pathway
  • MLP runs from the midbrain through the subcortex
  • MLP is a reward circuit is a reward circuit linked to addiction/motivation
  • excess dopamine leads to positive symptoms
  • mesocortical pathway
  • MCP runs from midbrain to prefrontal cortex
  • MCP is involved in managing executive function (attention, control, language)
  • low dopamine leads to negative symptoms
• evidence for the genetic explanation

  • family studies have found that children of a person with SCZ has a higher risk of 13%, compared to the general population risk of 1%
  • twin studies have found that concordance rates for identical twins are 48% vs 17% for non-identical twins
  • link between genetics and SCZ
  • can't be entirely genetic - limited explanation
• evidence for the dopamine hypothesis

  • Leucht et al - meta analysis
  • all antipsychotic drugs (which impact on dopamine) shown to be better than placebos at improving positive and negative symptoms
  • 64% placebo relapse rate vs 27% AP relapse rate
  • supports dopamine hypothesis
  • however, some people who took the placebo got better and some who took the actual AP got worse and therefore SCZ can't be purely neural