genetic explanations

• genetic vulnerability

  • genes are involved in the individual vulnerability to OCD
  • Lewis (1936) found that in an OCD study, out of the people who had OCD 37% had parents with OCD and 21% had siblings with OCD
  • this suggests OCD runs in families
  • according to the diathesis stress model, some environmental stress is needed to trigger OCD
• more than one gene involved (polygenic)

  researchers have identified genes which create a vulnerability for OCD called candidate gene. it has also been found that there are in fact over 230 genes involved in the condition.
• examples of genes involved

  • COMT gene: results in high levels of dopamine
  • SERT gene: linked to low levels of serotine
• What is a strength of genetic explanations for OCD?

  Twin studies
• What did Billett (1998) analyze in his study?

  14 twin studies on genetic inheritance of OCD
• What was the risk of developing OCD for MZ twins compared to DZ twins according to Billett (1998)?

  MZ twins had double the risk
• Why is the diathesis-stress model considered a better explanation for OCD?

  Because concordance rates are never 100%
• What is a counter-argument against twin studies in genetic research?

  They overlook environmental similarities of twins
• What difficulty arises from the findings of twin studies regarding OCD?

  Determining if genes or environment influence OCD
• what is a limitation of genetic explanations?

  • may be co-morbidity with depression
  • this depression probably involves disruption to the serotonin system
  • maybe the serotonin levels are disrupted because the patients are depressed, challenging the view that OCD is caused by lower serotonin levels