Explanaition

• OCD


  condition characterised by obsessions and compulsions
• Lewis - genetic vulnerability

  • 37% of parents with OCD
  • 21% siblings with OCD
• candidate genes 


  genes that create vulnerability (e.g. 5H1-D - transport serotonin)
• Aetiologically heterogeneous 


  different variations of genes can cause OCD
• diathesis-stress model 


  • certain people more likely to develop a mental disorder but is not certain
  • some environmental stress (experience) is necessary to trigger the condition
• Taylor - polygenic meta-analysis 


  230 candidate genes associated with regulating mood in OCD (e.g. dopamine + serotonin)
• genetic explanaition points


  • genetic vulnerability
  • candidate genes
  • aetiologically heterogeneous
  • polygenic
  • diathesis-stress
• neural explanations 


  • role of serotonin
  • decision-making systems
• Decision-making


  impaired decision-making due to impairment of the temporal frontal lobe
• Unpleasant emotions


  left hippocampal gyrus
• Structure of the brain

  left hippocampal gyrus (regulating mood)

  temporal frontal lobes (decision-making)
• Nestadt et al - twin studies

  68% twins MZ

  31% twins DZ

  Diagnosed family member = you are 4 X more likey to be diagnosed with OCD
• Kiara et al - diathesis-stress

  half OCD patients experienced trauma

  genetic vulnerability only increases the risk of development if there is a stressful environmental trigger

  Biological explanation is deterministic - ignores environmental factors
• Ahmari et al - mice


  little predictive value due to number of candidate genes

  BUT

  found genes associated with repetition

  BUT

  cannot apply to humans
• Neural research support -

  antidepressants that work on serotonin are effective in reducing OCD symptoms

  suggest serotonin's envolvement
• Not spekal neural system - comorbidity

  serotonin-OCD link not unique to OCD

  comorbidity of clinical depression

  so serotonin levels could be due to depression