Biological approach to explaining OCD

• What does this approach suggest about disorders?

  They are inherited- through the inheritance of genes
• State the three main concepts to genetic explanations for OCD

  • COMT gene
  • SERT gene
  • Diathesis-stress
• state the two main concepts of neural explanations for OCD

  • Abnormal levels of neurotransmitters
  • Abnormal brain circuits
• State two advantages of this approach to explaining OCD

  • 😊research support in twin studies (nesdadt et al) analysis of 14 twin studies shows OCD is more common in monozygotic twins that dizygotic twins
  • 😊support for drug therapy- ssri beneficial for 60% of people with OCD (Zohar et al) as they increase seratonin levels
• Explain how the COMT gene leads to people developing OCD

  • COMT gene is responsible for the production of COMT, COMT regulates production of neurotransmitter dopamine
  • One form of the COMT gene (allele) found to be more common in people with OCD than those without OCD
  • This variation causes reduced activity of the COMT gene and higher levels of dopamine
• Explain how the SERT gene can lead to people developing OCD

  • Affects serotonin transport, creating lower levels of serotonin
  • These lower levels implicated in OCD
• Describe the theory behind the distress stress model

  • Idea of simple link between one gene and a complex disorder like OCD is unlikely
  • Each individual gene only creates a vulnerability (diathesis) for OCD, as well as other conditions
  • Other factors (stressors) in the environment affect what condition develops or whether any condition develops
  • Some people can posses COMT or SERT gene but suffer no ill effects
• Describe how the levels of neurotransmitters are implicated in the development of OCD

  • DOPAMINE- levels thought to be high in people with OCD- high dopamine levels induce stereotyped movements typical of those with OCD
  • SEROTONIN- low levels of serotonin found in people with OCD- antidepressants increasing serotonin activity reduce OCD symptoms
• Describe how abnormal brain circuits are implicated in the development of OCD. What evidence is there to support these explanations?

  • Caudate nucleus (located in the basal ganglia) normally suppresses signals from the OFC to the thalamus about things that are worrying
  • But when nucleus is damaged, fails to suppress minor worry signals
  • these signals alert the thalamus, which sends signals back to OFC, acting as worry circuit
  • PET scans of patients with OCD show that while symptoms are active, there are increased activity levels in the OFC
• How are serotonin and dopamine linked to the worry circuit?

  • Serotonin- (Comer) plays key role in operation of caudate nucleus and OFC, abnormal levels causes the areas to malfunction
  • dopamine- main neurotransmitter of the basal ganglia, (where the caudate nucleus is located) high levels of dopamine link to the overactivity of this region
• State two disadvantages to the biological approach to explaining OCD

  • ☹️doesn’t establish causality. Not clear whether abnormalities (reduced serotonin or increased dopamine) causes OCD, or are a result of OCD
  • ☹️alternative explanations- psychological explanations- two process model can be applied to OCD- neutral stimulus (eg-dirt) associated with anxiety. Association maintained because anxiety-causing stimulus is avoided. Treated with exposure and response prevention (ERP) which is very similar to systematic desensitisation
• what is concordance rate?

  measure of genetic similarity