Explaining OCD (biological)

• P: evidence for the genetic basis of OCD comes from studies of first-degree relatives and twin studies

  E: Nestadt identified 80 patients with OCD and 343 of their first degree relatives and compared them with 73 control patients without mental illness and 300 of their relatives. They found that people with first degree relative with OCD had a 5x greater risk of having OCD. A meta analysis of 14 twin studies found that MZ twins were more than twice as likely to develop OCD.
• link for family and twin studies

  L: this evidence points to a clear genetic basis for OCD, but the fact that concordance rates are never 100% means that environmental factors must play a role too.
• P: evidence of the role of genes in OCD comes from studies of people with other disorders

  E: pauls and leckman studied patients with tourettes and their families, and concluded that OCD is one form of expression of the same gene that determines tourettes. Furthermore, it is reported that two out of every three patients with OCD also experience at least one episode of depression

  L: this all supports the view that there is not one specific gene of genes unique to OCD, but they act as a predisposing factor towards obsessive-type behaviour
• P: many studies demonstrate the genetic link to abnormal levels of neurotransmitters

  E: menzies used MRI to produce images of brain activity in OCD patients and their immediate family members without OCD and also a group of unrelated healthy people. OCD patients and their close relatives had reduced grey matter in key regions of the brain.

  L: this supports the view that anatomical differences are inherited and these may lead to OCD in certain individuals. menzies concluded that in the future, brain scans may be used to detect OCD risk.