Evaluation

• Nestadt reviewed twin studies into OCD

  Monozygotic twins had a concordance rate of 68%

  Dizygotic twins had a concordance rate of 31%
• P - Strength , Supporting Evidence

  Nestadt - reviewed twin studies and found 68% concordance rate in MZ twins and 31% in DZ twins

  MZ have more genes shared so concordance rate makes sense for this explanation

  D - However , MZ concordance rate is not 100% meaning that this cannot be a full explanation of OCD
• P - Limitation , Opposing Evidence

  Cromer - over half her sample had experienced a traumatic event and OCD was more severe in those with multiple traumatic events

  Environment and experiences play a factor in OCD development

  Over half the sample may skew results

  D - However , correlation does not prove causation

  Traumatic events may have occurred as a result of OCD and so we cannot know for sure if traumatic events cause OCD
• P - Limitation , Issues with Research into Candidate Genes

  Difficult to find candidate genes for OCD in humans

  Most findings come from animal research

  While we share many genes our brain structures are vastly different and more complex

  D - Furthermore , difficulty findings candidate genes may mean that they are limited making the theories 230 assumption false or do not exist