Biological approach: OCD

• genetic explanation of OCD

  OCD is polygenic - several genes involved

  Taylor - may be as many as 230 genes involved, genetic variations contribute to the different types of OCD:

  • COMT gene - regulates dopamine high levels of dopamine associated with OCD patients
  • SERT gene - linked to serotonin, low levels of serotonin associated with OCD
• neural explanations of OCD

  neurotransmitters

  • Piggot - drugs which increase level of serotonin in the synaptic fap are effective in treating patients with OCD
  • dopamine - high levels associated with compulsive behaviour

  brain structure

  • two main brain regions - basal ganglia, orbitofrontal cortex
  • basal ganglia - patients who suffer head injury develop OCD-like symptoms
  • orbitofrontal cortex - higher activity in patients with OCD resulting in compulsions
• Biological approach to explaining OCD AO3

  + research support in family studies:

  • Lewis - 37% patients with OCD had parents with disorder and 21% had siblings with OCD
  • Nestadt - individuals with first degree relative with OCD up to 5x more likely to develop disorder

  + support from twin studies:

  • Billett - meta analysis of 14 twin studies - MZ twins had double risk of developing OCD vs DZ twins

  -difficulty understanding neural mechanisms involved in OCD - can't establish cause and effect
• Drug therapies - SSRI

  when serotonin is released from the pre-synaptic cell into the synapse, it travels to the receptor sites on the post-synaptic neuron. serotonin that is not absorbed in post synaptic neuron is reabsorbed into the sending cell

  SSRI increase the level of serotonin preventing it from being reabsorbed