(A03)The Biological Explanations of OCD

• There is good supporting evidence (Genetics)


  Evidence from a variety of sources for the idea that some people are vulnerable to OCD due to their genetic make-up. Best source is twins studies
• Nestadt et al study


  Reviewed previous twin studies and found 68% of identical twines shared OCD as opposed to 31% of non-identical twins. Suggests genetic influence on OCD
• Too many candidate genes (Genetics)

  Psychologists have been much less successful at pinning down all of the genes involved: several genes are involved and each genetic variation only increases the risk of OCD by a fraction. Provides little predictable value
• Environmental risk factors (Genetics)

  Cromer et al found that over half of OCD patients in their sample had a traumatic event in their past and that OCD was more severe in those with more than one trauma. Suggests OCD can't be entirely genetic in origin: more productive to focus on environmental causes because we are more able to focus on this as well
• There is more supporting evidence (Neural explanations)

  Evidence to support role of some neural mechanisms in OCD. Some anti-depressants work purely on the serotonin system increasing levels of this neurotransmitter. Such drugs are effective in reducing OCD symptoms and this suggests the serotonin system is involved with OCD.
• Biological processes

  OCD symptoms form part of a number of other conditions that are biological in origin- Parkinson's disease. Suggests biological processes that cause the symptoms in those conditions may be responsible to OCD
• It is not clearly exactly what neural mechanisms are involved (Neural explanations)

  Cavedini states that studies of decision making have shown that these neural explanations are the same systems that function abnormally in OCD
• Brain systems


  Researchers also identified other brain systems that may be involved sometimes. Thus, we cannot claim to understand the neural mechanisms in OCD
• We should not assume the neural mechanisms cause OCD (Neural explanations)


  Evidence suggesting various neurotransmitters/structures of the brain do not function normally in patients with OCD. This is not the same as saying that this abnormal functioning causes the OCD. These biological abnormalities could be the result of OCD rather than its cause
• The serotonin-OCD link may be simply co-morbidity with depression (Neural explanations)


  Many people who suffer OCD become depressed. Having two disorders= co-morbidity. This depression involves the disruption to serotonin system so it could therefore simply be the serotonin system is disrupted in many patients with OCD because they are depressed too
• Twin studies are flawed as genetic evidence (Genetics)


  Twin studies overlook the fact that identical twins may also be more similar in terms of shared environments and state identical twins are more similar in terms of genes