AO3

• Research support family and twin studies: Nestadt et al (2000) found that people with first-degree relatives with OCD had a 5x greater risk of having the illness themselves. A meta-analysis of 14 twin studies found that MZ twins were more than twice as likely to develop OCD if their co-twin had the disorder compared to DZ twins (Billet et al., 1998)
• Real-world application: It is presumed that there is a simple relationship between a disorder and genes/areas of brain which has led to the mapping of the human genome, screening fertilised eggs, gene therapy, MRI scans to detect risk etc. However, this is not the case and human genome mapping raises lots of ethical issues
• Weakness - Twin and family may also be more similar in terms of shared environments (compared to non-identical twins who have quite different experiences, one boy one girl). Thus the outcome of OCD is a result of their environment not genes. This is further supported by the fact that concordance rates are never 100% = biological approach to OCD is reductionist
• Alternative explanations— the two-process model - NS associated with anxiety, this association is maintained due to avoidance. This has been supported by the success of treatment ERP – exposure and response prevention