biological explanation

• genetic explanations

  • diathesis stress model → certain genes leave some people more likely to suffer a mental disorder but it is not certain - some environmental stress is necessary to trigger the condition
  • candidate genes → create vulnerability for OCD, some of which are involved in regulating the development of serotonin
  • polygenic → not caused by one single gene (around 230)
  • different types → may be the result of particular genetic variations, such as hoarding disorder and religious obsession
• evaluation of genetic explanation

  strength

  • research to support → nestadt (2010) reviewed twin studies where 68% of mozozygotic twins both had OCD compared with 31% of dizygotic twins

  limitations

  • methodological problems studying twins → families also share the same environment
• neurotransmitters

  • responsible for relaying information from one neuron to another
  • dopamine levels are thought to be higher in OCD people (based on animal studies done by szechtman et al.)
  • lower levels of serotonin are associated with OCD (based on how antidepressant drugs are an effective treatment)
  • OCD is triggered by communication problems between the brain's deeper structures and the front part of the brain which use serotonin to communicate
• brain structures

  • basil ganglia → coordinates movement and supresses some emotion
  • frontal lobe (orbitofrontal cortex) → converts sensory information into thoughts and actions
• worry circuit

  the frontal lobe sends signal to the basal ganglia to worry about things →

  the basil ganglia is supposed to supress some worries →

  if it is damaged, patients have been known to suffer with OCD-like symptoms as BG cannot supress worries →

  as a result the worry goes back to the frontal lobe →

  the frontal lobe converts the worry into actions (compulsions) which means the sufferer will repeat certain behaviours to reduce the worry
• evaluation of neural explanation

  strength

  • practical application → evidenced by the treatment of SSRIs as they increase the level of serotonin in the brain → suggests abnormal biochemistry is involves

  limitations

  • this link is a correlation which does not suggest cause and effect → we don't know whether abnormal neural systems cause OCD or whether OCD causes abnormal neural systems
• evaluation of biological explanation overall

  • reductionist → what about other causes of OCD? e.g. cognitive/ environmental?
  • research by cromer et al (2007) found that the other half of their OCD sample had experienced a traumatic event in their past and OCD was more severe in those who had such experiences