The Biological approach to explaining OCD

• Genetic explanation

  • Inherit OCD form our parent and acquired due to specific genes
  • These are known as candidate genes
• Candidate genes

  • Specific genes that leads to vulnerability to OCD
  • EG - 5-HTT gene
  • Responsible for transport of serotonin
  • Ozaki et al found a mutation in the 5htt gene in families with history of OCD
  • OCD may be polygenic
  • Several genes contributes to OCD
  • Taylor's metanalysis found 230 genes involved in OCD
• Neural explanation for OCD

  Serotonin - regulates mood - facilitate synaptic transmission

  OCD - Serotonin removed too quickly

  Leads to moods associated with OCD

  Dopamine levels - Abnormally high in OCD - linked with anxiety + inability to stop foucsing on obessive thoughts
• Abnormal brain circuit

  Orbitofrontal cortex - send worry signals to the thalamus

  Mediated by the caudate nucleus in the basal ganglia which supresses minor thoughts but let major ones through

  Thalamus responds to the worry signals + innate a response

  • In someone with OCD, problems with the caudate nucleus - allows minor worry signals to the thalamus
  • Leads to the thalamus to respond to both minor + major worries
  • Leading to compulsions
• Supporting evidence - Brain studies

  • Neustadt et al - reviewed twin studies into COD
  • MZ 68% CR , DZ 31%
  • SB - shows as the proportion of shared genes increases - the likelihood of developing OCD also increases
  • Shows OCD develops due to genetic factors
  • Increases validity
• practical application

  • led to the development of SSRI
  • Which blocks the reuptake of serotonin
  • To prolong serotonin influence in the synapse
  • Soomro et al - found evidence that the impact of ssri was effective 70% of cases
  • Since the treatment is effective we can assume the underlying theory is also valid
  • This increases validity of the theory
• Too simplistic + stress diathesis model offers a better arguement

  • According to the model our genes influences if we get OCD or not. However it is actually due to our environmental factors
  • Cromer et al - found more then half of OCD patients had traumatic pasts and that OCD was even more severe if they had more then one
  • WB - shows OCD cannot entirely be genetic in origin
  • Traumatic events may acts as a contributory trigger
  • It starts OCD
  • We need to consider the genetic + environmental factors to have a holistic understanding