Genetic explanation

• Genetic explanation:

  • A popular explanation for mental disorders is that they are inherited
  • This would mean that individuals inherit specific genes from their parents that are related to the onset of OCD
• Genetic explanation: Twin studies

  Carey and Gottesman (1981)

  • Found identical twins showed a concordance rate of 87% for obsessive symptoms and features compared to 47% in non-identical twins

  This difference suggests that genetic factors are moderately important 
• Genetic explanation: Twin studies

  Van Grootheest (2005)

  • Reviewed twin studies on OCD and found that all studies reported higher concordance rates for identical compared to non identical twins
  • The overall conclusion was that there is a moderate genetic influence on the development of OCD

  However, the concordance rates for identical twins were overall short of 100%, indicating that environmental factors are of major importance
• Genetic explanation: Family studies

  Nestadt (2000)

  • Identified 80 patients with OCD and 343 of their first-degree relatives 
  • Compared them with 73 control patients without mental illnesses and 300 of their relatives 
  • They found lifetime incidence of OCD was higher in relatives of OCD patients (11.7%) in comparison to relatives of healthy controls (2.7%)
• OCD is polygenic

  • OCD is not caused by one single gene but a combination of genetic variations that together significantly increase vulnerability