AO3 explaining OCD

• family and twin studies

  Nestadt - 80 patients with OCD and 343 of their first-degree relatives. 73 control people and 300 of their relatives.

  people with first—degree relative with OCD have 5x greater risk of having OCD themselves.

  Billett et al - meta-analysis of 14 twin studies of OCD found, identical twins more than 2x as likely to develop OCD if their co-twin had it than fraternal twins.
• Tourette’s syndrome and other disorders

  not one specific gene unique to OCD.

  Pauls and Leckman - OCD is a form of expression of the same gene that determines Tourette’s.

  obsessional behaviour in OCD and Tourette’s found in autistic children and anorexia nervosa - differentiates them from those with bulimia.

  Rasmussen and Eisen - patients with OCD experience at least one episode of depression.
• research support for genes and OFC

  Menzies et al - MRI to produce images of brain activity in OCD patients, their immediate family members without OCD and unrelated healthy people.

  OCD patients and their immediate family had reduced grey matter in regions of the brain including OFC.
• real world application


  one of two parents may have the COMT gene, mother’s fertilised eggs could be screened - giving parents the choice of whether to abort the egg or not.

  alternatively - gene therapy to turn genes “off” so that disorder is not expressed.

  BUT presumes relationship between gene and OCD is simple, which may not be the case. also ethical issues.
• alternative explanations


  two-process model can be applied to OCD. neutral stimulus associated with anxiety, association is maintained because anxiety-provoking stimulus is avoided. obsession is formed and then link is learned with compulsive behaviours.

  success of treatment for OCD - exposure and response prevention.

  Albucher et al - between 60 and 90% of adults with OCD have improved using ERP.