Genetic OCD explanation

• Biological approach to explaining OCD

  Assumption that our thoughts and behaviours are a result of physiological internal processes and are innate within us
• Genetic explanation for OCD

  Onset of OCD is a result of our genetic make-up that we are born with
• We inherit 50% of our chromosomes from our mother and 50% from our father
• Twin studies


  • Monozygotic (identical) twins share 100% of their DNA, meaning they are born with the same genotypes
  • Dizygotic (non-identical) twins share less genetic material
• If OCD is genetic

  We would expect a higher concordance rate in monozygotic twins compared to dizygotic twins
• Miguel et al. (2005) found a 53-87% chance of one monozygotic twin developing OCD if the other already had it, compared to a 22-47% chance in dizygotic twins
• It is unlikely that one specific gene causes OCD, but rather a combination of genes that determine an individual's level of vulnerability to the condition (polygenic)
• Taylor (2013) found up to 230 different genes may be involved in OCD
• COMT gene


  • Involved in the regulation of dopamine
  • One form of the COMT gene is more common in OCD patients than people without the disorder, producing lower activity of the COMT gene and higher levels of dopamine
• SERT gene (also called 5-HTT gene)


  • Affects the regulation of serotonin, leading to lower levels in the brain
  • Patients with OCD are more likely to carry two copies of the long allele of the 5-HTT gene compared to controls
• We are born with our DNA that does not change (genotype), but the way our cells and genes are activated (which are turned on) can lead to changes in mental illness
• These outside factors can affect the way the gene expresses (phenotype)
• An individual may have a genetic vulnerability to OCD (among other conditions), but other factors affect whether mental illness develops (diathesis-stress)