biological explanation

• 🧬 genetic explanation

  • runs in families
  • polygenic
  • genes are involved in dopamine transmission, immune function and brain development
  • epigenetics
• who studied concordance rate in families?

  gottesman
• 📖 gottesman's family concordance study

  • MZ twins = 48%
  • DZ twins = 17%
• who studied genetic variations in schizophrenia?

  ripke et al
• 📖 ripke et al

  108 separate variations
• 🧠 neural correlates

  patterns of brain structure or activity linked to symptoms
• ➖ negative symptoms & neural correlates

  • ventral striatum has reduced activity

  Juckel et al - lower activity levels correlates with severity of avolition
• ➕ positive symptoms & neural correlates

  • superior temporal gyrus
  • anterior cingulate gyrus

  Allen et al - increased activity when experiencing hallucinations
• 🏛️ classic dopamine hypothesis

  symptoms are caused by overactivity of dopamine

  • subcortical areas linked with positive symptoms
• 💻 modern dopamine hypothesis

  • hyperdopaminergia - positive symptoms
  • hypodopaminergia - negative symptoms
• ✅ strength of genetic - support

  twin studies have higher concordance rates

  • gottesman - 48% concordance in MZ twins compared to 17% in DZ twins
  • strongly suggests a genetic component
  • heredity
• ❌ limitation of genetics - concordance

  concordance of MZ twins isn't 100%

  • only 48% of MZ twins developed schizophrenia
  • environmental influences must contribute
  • challenges sufficiency
• ✅ strength of genetics - specific

  genome-wide studies

  • ripke et al - found 108 different variations
  • biological markers for early diagnosis or targeted treatments
  • adds credibility and practical value
• ✅ strength of neural correlates - evidence

  brain scans show structural abnormalities

  • enlarged ventricles and reduced grey matter in prefrontal cortex
  • linked to cognitive impairments and negative symptoms
  • strong empirical support
• ❌ limitation of neural correlates - correlation

  result of schizophrenia rather than the cause

  • unclear whether abnormalities precede onset of symptoms or develop as a consequence
  • lacks causality
  • weakens explanatory power
• ✅ strength of neural correlates - value

  predictive value

  • longitudinal studies suggest abnormalities appear before the first psychotic episode
  • early detection can lead to timely interventions
  • clinical usefulness
• ✅ strength of dopamine hypothesis - support

  effectiveness of antipsychotic drugs

  • chlorpromazine blocks dopamine receptors and reduces positive symptoms
  • dopamine overactivity is a cause
  • strong pharmacological evidence
• ❌ limitation of dopamine hypothesis - incomplete

  can't account for all symptoms

  • mainly explains positive symptoms
  • other neurotransmitters e.g. glutamate may be involved
  • limits comprehensiveness
• ✅ strength of dopamine hypothesis - revised

  original version was updated to include underactivity

  • hypofunction in prefrontal cortex is linked to negative symptoms
  • better explanatory power
  • enhancing the credibility