Explanations of OCD

• Biological explanations of OCD

  • Genetic explanation
  • Neural explanation
• State the neural explanation

  The neural explanation states that OCD is caused by disrupted communication between the basal ganglia and the orbitofrontal cortex
• Explain the neural explanation of OCD

  The inhibitory signals from the basal ganglia are weakened, causing hyperactivity of the orbitofrontal cortex, which leads to obsessive thoughts and worries
• State the genetic explanation of OCD

  • According to the genetic explanation, OCD is a genetic condition which is inherited
  • A number of gene alleles have been associated with increased risk of developing OCD
• Explain the genetic explanation for OCD

  • For instance, studies have indicated that carrying the long allele of the SERT gene is a risk factor for OCD
  • The SERT gene controls the re-uptake of serotonin at the synapse, with the long allele leading to increased serotonin re-uptake (and therefore, a decrease in serotonin levels at the synapse)
  • Since serotonin is an inhibitory neurotransmitter, this decrease in serotonin may contribute to hyperactivity in the orbitofrontal cortex
• Strength: Supporting evidence for the Genetic explanation

  • Support for the genetic explanation of OCD comes from twin studies comparing concordance rates in monozygotic and dizygotic twins
  • For instance, in a review of multiple twin studies, Billet et al reported concordance rates of 68% for OCD in monozygotic twins, and concordance rates of 31% for dizygotic twins.
  • Since the concordance rates were bigger for monozygotic twins than for dizygotic twins, this suggests that genetics does contribute to OCD
• Limitation: twin studies supporting the genetic explanation of OCD

  • For instance, twin studies make the assumption that monozygotic twins and dizygotic twins have the same amount of shared environment
  • However, this assumption might not be true, because identical twins are more likely to be treated similarly by their friends and family than dizygotic twins
  • This means that the high concordance rates for OCD observed in monozygotic twins might actually be caused by shared environmental factors rather than shared genetic factors
• Strength: Research support for the neural explanation of OCD

  • Support for the neural explanation of OCD comes from brain imaging studies
  • For instance, Saxena and Rauch conducted a review of multiple fMRI brain imaging studies, and found that people who has OCD has increased activity in their orbitofrontal cortex compared to a healthy control group
  • This supports the idea that OCD is caused by hyperacitivty in the orbitofrontal cortex
• Strength: biological approach of OCD

  • A strength of the biological approach is that it has been applied to develop treatments for OCD
  • For instance, one popular treatment for OCD is SSRIs: drugs that increase the level of serotonin available at the synapse.
  • SSRis have been found to be effective in treating OCD
  • This is important because it demonstrates that the biological approach can successfully be used to explain and treat OCD
• Counter argument: development of treatments for OCD

  • However, it is worth noting that when patients stop taking SSRIs, they experience rapid relapse of symptoms
  • This suggests that SSRIs may be suppressing symptoms rather than treating the underlying causes of OCD
  • This is a problem because it places limitations on the support for the biological approach to OCD