The Biological Approach to OCD: Genetic explanation

• Gene

  a segment of DNA that controls the production of one protein
• Allele

  Different versions of the same gene
• Inheritance

  the process of passing down gene alleles from parent to child
• Genetic explanation of OCD: focus

  • this explanation says that we can inherit OCD
  • There are specific alleles on different genes that can increase a person's risk of developing OCD
• The SERT gene

  • Produces reuptake proteins that carry serotonin back into the presynaptic terminal
  • the more protein that is produced the less serotonin available at the synapse
• Alleles of the SERT gene

  • the long allele produces more reuptake proteins than the short allele causing less serotonin to be available at the synapse therefore causing less inhibition of neural activity in the post synaptic neuron.
  • Due to this the long allele is associated with OCD.
• Bilet et al

  • conducted the review of twin studies and found that the concordance rate for OCD was 68% for monozygotic twins and 31% for dizygotic twins
  • Indicates that OCD is partially inherited
• Nestadt et al: family studies

  • recruited a group of patients with OCD and a control group of healthy participants
  • Interviewed the relatives of the participants in both groups to find out how many of these relatives also had OCD
  • The researchers found out that 12% of participants with OCD had a relative who also had OCD.
  • However only 3% of participants in the control group had a relative with OCD.
  • These findings suggest that OCD is partially inherited
• Hu et al

  • supports the idea that carrying the long allele on the SERT gene increases a persons likelihood of developing OCD.
  • They conducted DNA analysis on a group of people with OCD and a control group with healthy participants
  • They found out that people with OCD were more likely to carry the long allele on the SERT gene than the participants in the control group.
• Limitations of twin studies

  • They assume that MZ twins and DZ twins have the same amount of shared environment
  • MZ twins are more likely to be treated the same than DZ twins
  • High concordance rates for OCD in MZ twins might be caused by shared environmental factors
• SSRIs: biological treatment for OCD

  • Block serotonin reuptake which means that there is more serotonin available at the synapses in the OFC
  • Leads to more inhibition of neural activity in the OFC reducing hyperactivity of neurons in this brain region
  • Reduces the worrying signals that cause obsessions and compulsions
• Strengths of biological treatments of OCD

  • Supported by studies
  • Soomro et al: reviewed 17 studies investigating effectiveness of SSRIs.
  • Found that 70% of the adults with OCD who were treated with SSRIs experienced an improvement in symptoms
  • Concluded that SSRIs are significantly more effective at reducing OCD symptoms than no treatment
  • Cost effective for healthcare services to provide
• Limitations of biological treatments to OCD

  • Biological treatments like SSRIs can cause side effects as they block serotonin reuptake in the whole brain.
  • Soomro et al: found that patients treated with SSRIs experienced side effects like nausea, headaches and insomnia
  • If patients stop taking SSRIs, they may relapse
  • May not be effective at treating the underlying cause of OCD on their own
  • There may be other causes such as cognitive factors that may contribute to OCD which also need to be treated
  • May need to combine treatments with cognitive treatments. e.g CBT
• O'Connor et al

  • found that combining biological and cognitive treatments for OCD could be more effective
  • CBT + SSRIs showed biggest improvements in symptoms.