Biological approach to explaining OCD

• What are the two explanations

  1. Genetic
  2. neural
• genetic explanation: candidate genes

  researchers have identified specific genes which create vulnerability for OCD called candidate genes

  • serotonin genes are implicated in the transmission of serotonin across synapses
  • dopamine genes are also implicated in OCD and many regulate mood

  both dopamine and serotonin are neurotransmitters
• genetic explanation: OCD is polygenic

  OCD is not caused by one single gene but several genes involved. Taylor (2013) found evidence that up to 230 different genes may be involved in OCD
• genetic explanations: different types of OCD

  one group of genes may cause OCD in one person but a different group of genes may cause the disorder in another person - known as aetiologically heterogenous

  there is evidence that different types of OCD may be the result of particular genetic variations such as hoarding disorder and religious obsession
• neural explanations: low levels of serationin

  neurotransmitters are responsible for relaying information from one neuron to another. for example if a person has low levels of Seratonin in then normal transmission of mood relevant information does not take place and mood and other mental processes are affected
• neural explanations: decision making impaired


  some cases of OCD, and hoarding disorder are associated with impaired decision making. this is turn may be associated with abnormal functioning of the lateral frontal lobes of the brain. the frontal lobes are responsible for logical thinking and making decisions
• Neural explanations: parahippocampal gyrus dysfunctional

  There is also evidence to suggest that an area called the left parahippocampal gyrus, associated with processing unpleasant emotions, functions abnormally in OCD
• one strength is evidence for the genetic explanation of OCD

  Nestadt (2010) reviewed twin studies and found that 68% of identical twins (MZ) shared OCD as opposed to 31% of non identical twins (DZ). marini and Stebnicki (2012) found that a person with a family member with OCD is 4x more likely to develop it as someone without. this means that people who are genetically similar are more likely to share OCD, supporting a role for genetic vulnerability
• one limitation of genetic explanation is the existence of environmental risk factors


  genetic variation affects vulnerability to OCD, but there are also environmental risk factors that trigger or increase the risk of OCD. Cromer (2007) found in one sample over half of pepole with OCD experienced a traumatic event. OCD severity correlated positively with number of traumas. this means that genetic vulnerability only provides a partial explanation for OCD.
• one strength of the neural explanation is supporting evidence

  antidepressants that work on serotonin reduce OCD symptons. this suggests that seratonin may be involved in OCD. also, OCD symptoms form part of conditions that are known to be biological in original e.g. Parkinson’s disease (Nestadt). this means that biological factors are likely to be involved in OCD
• one limitation of the neural model is there is no unique neural system

  many people with OCD also experience depression. this depression probably involves disruption to the action of serotonin. it could simply be that serotonin activity is disrupted in many people with OCD because they are depressed as well. this means that serotonin may not be relevant to OCD symptoms.