biological explanations - OCD

• biological explanations of OCD include those which are genetic and neural
• genetic explanations for OCD

  • diathesis stress model
  • candidate genes
  • polygenic
• genetic explanation for OCD

  • OCD has strong biological component
  • genes involved with those who have vulnerability to OCD
  • lewis observed of his OCD patients - 37% had parents with OCD, 21% had siblings with OCD
  • suggests OCD runs in families - means there is genetic vulnerability of having OCD - passed on through generations
• diathesis stress model

  • explains how OCD is triggered
  • diathesis (biological part of model) - individuals may have genes making them more vulnerable to OCD
  • stress (environmental part of model) - if individual experiences right stressors in their environment it may result in development of OCD
• candidate genes - those which create vulnerability for OCD - some are involved in development of regulating development of serotonin system
• OCD is polygenic

  • means OCD is caused by involvement of several genes and not just one
  • research support - taylor analysed findings from previous studies - found evidence of up to 230 genes involved in OCD across sample - dopamine and serotonin associated
• dopamine is the pleasure neurotransmitter

  • addiction, movement + motivation
  • repeat behaviours to lead to dopamine release
• serotonin - mood neurotransmitter

  • contributes to wellbeing + happiness
  • helps sleep cycle
  • affected by exercise and light exposure
• there are different types of OCD which are based on different types of genes - pretty impossible to understand key genes within OCD
• evaluation for genetic explanations for OCD

  • supporting evidence (+)
  • too many candidate genes (-)
  • minimises risk factors (-)
• supporting evidence for genetic explan (+) eval

  • strength of genetic explanations for OCD includes there being research to support
  • nastadt reviewed twin studies - found 68% of identical twins shared OCD - opposed to 31% of non identical twins - findings suggest strong genetic component to OCD
  • however - if OCD was purely down to genetics there should be 100% concordance rate due to identical twins sharing 100% DNA
  • overall - genetic explan is strong as theres evidence supporting influence of genes on development of OCD
• too many candidate genes (-)

  • limitation of genetic explan is that it is difficult to identify all genes involved in causing OCD - cannot specify exact/ all genes due to OCD being polygenic
  • psychologists havent been successful at pinning down all genes involved in OCD due to several genes being involved and each diagnosis has genetic variation
  • unlikely genetic explan will be useful as it provides little predictive value
  • therefore its limited as it may not be useful in identifying individuals risk of developing OCD
• minimises risk factors (-)

  • limitation of genetic explan for OCD is that it only considers biological factors
  • found environmental factors can also trigger or increase risk of developing OCD (diathesis stress model)
  • example - researcher found over half OCD patients in sample had traumatic event in past and OCD had been more severe since occurance
  • suggests OCD is not 100% genetic - explan is limited as it doesnt consider all factors which could be involved
• neural explanations

  • role of serotonin
  • decision making systems
• role of serotonin

  • serotonin is neurotransmitter which helps regulating mood|
  • found to be low levels of serotonin in OCD - reduction in functioning of serotonin system in brain
• those with OCD lack serotonin which means messages arent passed on between neurons effectively
• synaptic transmission (applied to OCD)

  1. action potential travels along presynaptic neuron - then reaches synapse
  2. action potential (electrical signal) triggers synaptic vesicles to release neurotransmitters (serotonin)
  3. neurotransmitters cross synapse (chemically) and then bind to receptor cells on postsynaptic neurons to then pass mmessage on
  4. neurotransmitters (serotonin) released from receptor cell and travels to next presynaptic neuron
• decision making systems

  • some cases of OCD seem to be associated with impaired (weakened) decision making
  • may be associated with abnormal functioning of lateral/frontal lobes (frontal lobes responsible for logical thinking and making decisions)
  • evidence suggesting area called left parahippocampal gyrus is associated with processing unpleasant emotions (left parahippocampal gyrus functions abnormally in OCD)
• evaluation points for bio explan for OCD

  • supporting evidence (+)
  • serotonin and OCD link may be down to comorbidity with depression (-)
  • cause and effect is unclear (-)
• supporting evidence (+)

  • strength of neural explan includes there is evidence supporting role of some neural mechanisms in OCD
  • example - some antidepressants work purely on serotonin system by increasing level of serotonin (neurotransmitters) - drugs are effective in reducing OCD symptoms which suggests serotonin system is involved in OCD
  • therefore strength of theory is that its supported by research using drugs
• serotonin and OCD link may be down to comorbidity with depression (-)

  • limitation of explanation includes link between serotonin and OCD could be due to co occurring depression
  • many who suffer OCD then become depressed (therefore experience 2 disorders at once - comorbidity)
  • depression occurring had probably involved the disruption to serotonin system (depression is associated with low mood)
  • therefore explan is limited as it could be that serotonin system is disrupted in many patients with OCD because they are depressed aswell
• cause and effect is unclear (-)

  • cause and effect of relationship is not known - could be that changes in brain are result of OCD rather than causing it in first place
  • weakens neural explanation