AO3: Biological approach to explaining OCD

• Brain Structure

  Should be evident in all OCD patients but isn't. This means that it could be a symptom of OCD rather than the cause, or it could just be structural abnormalities.

  Just because a structure is inactive doesn't mean to say that it does that thing- it is a correlate.

  An underactive caudate nucleus could be the result of having OCD for a long time. It could mean that it gets worse over time which makes the differences more pronounced.
• Serotonin

  Hu (2006) compared serotonin activity in 169 OCD sufferers and 253 non-sufferers, finding serotonin, finding serotonin levels to be lower in OCD patients, which supports the idea of serotonin levels being associated with the onset of the disorder.
• Serotonin

  However, it could again be a symptom of OCD.
• Serotonin: SSRIs

  SSRIs are selective serotonin reuptake inhibitors, they stop serotonin from being taken back up into the neurone which lowers the symptoms of OCD.

  However, SSRIs do not work for everyone, if serotonin was the cause of OCD, they would work for everyone.
• Genetics: Billet

  Billet researched monozygotic twins (68%) and found that they are more than twice as likely as dizygotic twins of suffering from OCD (31%).

  The closer you are genetically to someone with OCD, the more likely you are to have it.

  (If it was solely caused by genetics however, the concordance rate would be 100%).
• Genetics: Nestadt

  Found that you are 5 times more likely to suffer from OCD than the general population if a first degree relative suffers from OCD. This suggests that it runs in families.
• Genetics

  Genetic explanations have poor predictive validity.

  There are too many candidate genes involved, it's difficult to isolate OCD to one specific gene, its likely to be polygenic (multiple genes/variations of genes).

  One candidate gene is unlikely because evolution would have gotten rid of it.

  The hSERT gene doesn't just effect OCD which makes genetics unlikely to be a useful explanation in explaining OCD.

  Diathesis-stress model: there could be underlying biology which triggers OCD.
• Biological reductionism

  This approach to explaining OCD ignores other factors and is reductionist. For example, the biological approach does not take into account cognitions and learning. Some psychologists suggest that OCD may be learnt through classical conditioning and maintained via operant conditioning. For example, dirt, a person avoids dirt and continually washes their hands. The hand washing is a compulsion reduces their anxiety and negatively reinforces their obsessions.