Psychopathology - Biological approach to explaining OCD

• What’s the biological approach to explaining OCD?

  Vulnerability to OCD can be affected by genetic make up & brain functioning
• What’s the 2 types of biological explanations?

  • Genetic explanation
  • Neural explanation
• Who’s study showed that genes are involved in vulnerability to OCD?

  Lewis
• What did Lewis find in his study of OCD?

  • Observed that of his OCD patients 37% had parents with OCD & 21% had siblings with OCD
  • Suggests OCD runs in families - genetic vulnerability to OCD passes on through generations
• What does the diathesis-stress model propose?

  Certain genes leave some people more likely to develop a mental disorder but not certain - environment is necessary to trigger it
• What are candidate genes?

  • Genes which researchers identified as creating a vulnerability to OCD
  • Some are involved in regulating development of the serotonin system
• How is OCD polygenic?

  • Isn’t caused by a single gene but a combination of genetic variations that together increase vulnerability
  • Taylor found up to 230 different genes may be involved in OCD
  • Includes those associated with dopamine & serotonin (mood regulation)
• What does it mean for OCD to be aetiologically heterogeneous?

  • Origins of OCD may vary from one person to another (a group of genes might cause OCD in one person but another group of genes might also cause OCD in another person)
  • Different types of OCD may be due to particular genetic variations e.g. hoarding disorder
• What does the genetic explanation concern?

  • Genes make up chromosomes & consist of DNA
  • DNA codes physical features & psychological features of organism
  • Genes transmitted from parents to offspring
• What are neural explanations of OCD?

  Genes associated witch OCD likely to affect neurotransmitter levels & brain structures
• What is the role of serotonin in neural explanations of OCD?

  • Low levels of serotonin means normal transmission of mood-relevant information doesn’t take place & a person can experience low moods
  • Some cases of OCD can be explained by a reduction in the functioning of the serotonin system in the brain
• How are the decision making systems involved in OCD (as neural explanations of OCD)?

  • Some cases of OCD seem to be associated with impaired decision-making (especially hoarding disorder)
  • Can be associated with abnormal functioning of the lateral of frontal lobes of the brain
  • Frontal lobes are responsible for logical thinking & making decisions
  • Left Parahippocampul gyrus is associated with processing unpleasant emotions (abnormal functioning in OCD)
• What are the evaluation points for genetic explanations of OCD?

  • Research support : Nestadt found 68% of MZ twins shared OCD as opposed to 31% of DZ twins. Family studies = research found person with a family with OCD is 4x more likely to develop it. Indicated genetic influence on development of OCD
  • Environmental risk factors : Genetic variation has role in OCD but it’s not entirely genetic in origin & environmental risk factors can trigger. Cromer found over half the OCD clients in the sample had experienced a traumatic event in the past. So genetic vulnerability = partial explanation
• What are the evaluation points for neural explanations of OCD?


  • Research support : Antidepressants working purely on serotonin are effective in reducing OCD symptoms which suggests the role of serotonin in OCD. OCD symptoms form part of conditions that are biological in origin (parkison’s disease). If biological disorder produces OCD symptoms then can assume biological processes underlie OCD.
  • Serotonin-OCD link might not be unique : Many with OCD also experience clinical depression. Co-morbidity (2 disorders together). Could be that serotonin activity is disrupted due to depression.