OCD

• What is compulsive behaviour?

  Repetitive behaviour performed to reduce anxiety (counting)
• What are obsessive thoughts?

  Recurrent, intrusive thoughts that are perceived as inappropriate
• Behavioural characteristics of OCD:

  • Compulsive behaviour
  • Avoidance
• Emotional characteristics of OCD:

  • Shame
  • Anxiety & distress
• Cognitive characteristics of OCD:

  • Obsessive thoughts
  • Cognitive strategies
  • Insight into excessive anxiety
• What is the association of the COMT gene allele with dopamine levels?

  It is associated with higher levels of dopamine.
• Which gene is involved in the transport of serotonin?

  SERT gene
• What is the relationship between serotonin levels and OCD?

  Lower levels of serotonin are associated with OCD.
• What does the diathesis-stress model suggest about OCD?

  It suggests genetic mutations lead to vulnerability for OCD, but other factors must also be present.
• What are the key genetic factors associated with OCD?

  • COMT gene: regulates dopamine production, associated with higher dopamine levels
  • SERT gene: involved in serotonin transport, lower serotonin levels linked to OCD
  • OCD is a polygenic disorder
• The caudate nucleus normally suppresses signals from the orbitofrontal cortex which sends signals to the thalamus about worrying. When it’s damaged it fails to suppress minor worries
• Biological explanations for OCD evaluation:

  • ✅ Evidence from twin studies - meta-analysis found that MZ twins had double the concordance rate for OCD than DZ twins
  • ❌ Ignores other factors - environment
  • ✅ Support for serotonin - when treated with drugs which increase the level of serotonin, symptoms decrease
  • ❌ Alternative two process model - OCD is learnt through classical conditioning. A neutral stimulus is associated with anxiety. An obsessions formed & compulsive behaviours are reinforced when anxiety reduces
  • ✅ Doesn’t blame the sufferer
• Anti-anxiety drugs for treating OCD

  • Benzodiazepines (Xanax) - Enhances the activity of the neurotransmitter GABA which increase the flow of chloride ions into brain which has a quietening effect
• Anti-depressants for treating OCD:

  • SSRIs (Zoloft) - increase levels of serotonin by blocking re-uptake at the pre-synaptic membrane
  • Tricyclics (Anafranil) - block reabsorption of serotonin & noradrenaline
• Drug therapy for OCD evaluation:

  • ✅ Effectiveness - evidence in studies, placebo & drug ❌ most studies only last a few months so no long term data
  • ✅ Practical - cheap & little time required
  • ❌ Possible side effects & addiction
  • ❌Only treats symptoms not underlying causes - patients relapse a few weeks after medication is stopped
  • ❌ Publication bias - exaggerates benefits of drugs - ethical issues