9. The Biological Approach to Explaining OCD

• 1. The Biological Approach to Explaining OCD

  OCD, biological nature:

  • Orbitofrontal = anxiety area, overstimulated.
  • Thalamus = safety behaviours, checking/cleaning; enlarged area.
  • Parahippocampal Gyrus = OCD, processes unpleasant emotions abnormally.
  • Frontal Lobes = decisions making/logical thinking = OCD, abnormality causes hoarding.
• 1a. The Biological Approach to Explaining OCD

  Neural Explanations of OCD:

  Serotonin:

  • Low levels = normal transmission of mood-relevant info not take place = mental processes affected.
  • Reduction in functioning of serotonin system (OCD).

  Dopamine:

  • High levels = role in development OCD.
  • PET scans = OCD, patients higher than normal level of neurotransmitters.
• 2. The Biological Approach to Explaining OCD

  Genetic Explanations:

  • Development due to genes.
  • Gene-mapping studies, compares genetic material between sufferers/non-sufferers - genes linked OCD.
  • Lewis (1936), 37% patients w/ parents w/ OCD; 21% siblings — genetic vulnerability inherited.
• 2a. The Biological Approach to Explaining OCD

  Genetic Explanations of OCD - Diathesis Stress Model:

  • Environmental stressors necessary to trigger OCD in genetic vulnerable.
• 2b. The Biological Approach to Explaining OCD


  • OCD - polygenic (multiple genes); Taylors (2013), 230 diff genes involved; include dopamine/serotonin.

  Candidate Genes:

  • Regulates serotonin system.
  • E.g. 5HTI-D beta (sert), transport of serotonin.
  • E.g. COMT, dopamine production.
  • OCD, genetically heterogenous; diff genes cause diff types OCD.
• The Biological Approach to Explaining OCD (Evaluation)

  Strength - Genetic Explanations:

  P - evidence support; twin/family studies.

  E - Nestadt et al. (2010), 68% identical twins (MZ) shared OCD; 31% non-identical (DZ).

  E - research found person w/ family member w/ OCD 4x likely develop it as someone w/o.

  L - some genetic influence on development of OCD.
• The Biological Approach to Explaining OCD (Evaluation)

  Limitation - Genetic Explanations:

  P - environmental risk factors.

  E - OCD not entirely genetic, environmental factors trigger risk development of OCD.

  E - Cromer et al. (2007), over 1/2 clients experienced traumatic event.

  L - more severe in people w/ trauma, genetic vulnerability partial explanation.
• The Biological Approach to Explaining OCD (Evaluation)

  Strength - Neural Explanations:

  P - supporting evidence.

  E - antidepressants that work only on serotonin effective in reducing OCD, suggests serotonin involved in OCD.

  E - OCD symptoms form conditions biological in origin e.g. Parkinson’s disease.

  L - if biological disorder produces OCD, biological factors (e.g. serotonin) responsible.
• The Biological Approach to Explaining OCD (Evaluation)

  Limitation - Neural Explanation:

  P - serotonin-OCD link not unique to OCD.

  E - OCD + clinical depression (co-morbidity).

  E - depression w/ OCD likely involves disruption to serotonin - problem when drawing link between OCD-serotonin.

  L - may be serotonin disrupted in OCD bc depressed too; serotonin may not be relevant in OCD symptoms.