biological approach to explain OCD

• OCD: repetitive behaviour + obsessive thinking
• genetics: diathesis stress model

  lewis - 37% OCD parents 21% OCD siblings
• twin study - nestadt et al

  MZ = 68% DZ = 31%
• some candidate genes involved in serotonin development serotonin - mood, cognition + memory e.g 5HT1-D affects serotonin across synapse

  dopamine - pleasure, satisfaction + motivation
• neural - decrease serotonin = affects mood

  imbalance in dopaminergic reward system = compulsions

  hoarding -> impaired decision making -> lateral frontal lobes

  associate OCD with left parahippocampus gyrus
• supporting evidence✅

  • taylor - 230 genes (polygenetic)
  • not useful, too many so decreases predictive value 🚫
• contradictory evidence🚫

  • diathesis - stress = environmental factors
  • cromer at al. - over half of OCD sample had a traumatic event
  • increase in trauma = increase in severity OCD
• no cause + effect 🚫

  • differences in neurotransmitters may be result of OCD rather than cause
• genetic explanation - suggests OCD is an inherited condition that passes across generations

  • candidate genes implicated as a possible cause for OCD: COMT, SERT. mutations in these genes are believed to result in the onset of OCD
  • however OCD is polygenic as taylor found 230 diff genes involved
• neural explanation

  • abnormal levels of neurochemicals implicated in OCD
  • low serotonin levels -> abnormal transmission of mood-related info may be linked to obsessive thoughts
  • abnormal functioning of orbitofrontal cortex (worry circuit) and parahippocampal gyrus