OCD - Explaining and Treating

• Dizygotic twins


  Non-identical twins who share around 50% of their genetic makeup, have a 31% concordance rate for OCD
• Concordance rates


  • Monozygotic twins (68%)
  • Dizygotic twins (31%)
• Genetic explanations


  Suggest OCD is inherited and that individuals inherit specific genes which cause OCD
• Genetic explanations


  • Focused on identifying particular genes implicated in OCD
  • Two genes have been linked to OCD: COMT gene and SERT gene
• COMT gene


  Associated with the production of an enzyme that regulates the neurotransmitter dopamine
• One variation of the COMT gene

  Results in higher levels of dopamine and is more common in patients with OCD, in comparison to people without OCD
• SERT gene (5-HTT gene)

  Linked to the neurotransmitter serotonin and affects the transport of serotonin, causing lower levels of serotonin which is associated with OCD (and depression)
• Neural explanations of OCD

  Focus on neurotransmitters as well as brain structures
• Neural explanations of OCD

  Suggest abnormal levels of neurotransmitters, in particular serotonin and dopamine, are implicated in OCD
• Neural explanations of OCD

  Suggest particular regions of the brain, in particular the basal ganglia and orbitofrontal cortex, are implicated in OCD
• Serotonin


  • Neurotransmitter believed to play a role in OCD
  • Regulates mood
  • Lower levels associated with mood disorders like depression
  • Reduced levels may be caused by SERT gene
  • Increasing serotonin levels with antidepressants is effective in treating OCD
• Dopamine


  • Neurotransmitter implicated in OCD
  • Higher levels associated with compulsive behaviours in OCD
• Brain regions implicated in OCD

  • Basal ganglia
  • Orbitofrontal cortex
• Basal ganglia


  • Brain structure involved in multiple processes, including the coordination of movement
  • Patients who suffer head injuries in this region often develop OCD-like symptoms, following their recovery
  • When the basal ganglia is disconnected from the frontal cortex during surgery, OCD-like symptoms are reduced
• Orbitofrontal cortex


  • Brain region which converts sensory information into thoughts and actions
  • PET scans have found higher activity in the orbitofrontal cortex in patients with OCD
  • Heightened activity in the orbitofrontal cortex increases the conversion of sensory information to actions (behaviours) which results in compulsions
  • The increased activity also prevents patients from stopping their behaviours