genes

• genetics

  -individuals inherit specific genes from parents that're related to onset of OCD
• gene


  section of DNA that codes for a protein
• COMT gene


  -may contribute to OCD

  -regulates production of dopamine

  -one form of COMT found to be more common in OCD patients

  -variation produces lower activity of COMT gene > causing higher dopamine levels
• SERT gene


  -affects transport of serotonin

  -variation of serotonin creates lower levels of neurotransmitter
• polygenic - Taylor


  -Taylor found evidence that there might be up to 230 different genes involved in OCD

  -OCD may be polygenic

  -not caused by one single gene > several involved
• ways to test if something is genetic in human Ps

  -family studies

  -twin studies
• family studies - Nestadt et al


  -studied patients with OCD and their first degree relatives

  -compared them with control patients and their first degree relatives

  -first degree relatives of OCD sufferers had 5x greater risk of OCD compared to control group
• dizygotic 


  share 50% of their genes
• monozygotic

  share 100% of their genes
• concordance rate - twin studies 


  -number of twins in each sample that both have disorder

  -higher number = more similar twin pairs are

  > more likely a genetic cause

  -MZ twins have higher concordance rate = genes

  -both sets of twins similar = environment
• twin studies - Nestadt et al


  -one MZ twin has OCD there was 68% chance that the other twin would also develop it

  -if one DZ twin had OCD there's only 31% chance of other twin also suffering

  -MZ have higher concordance rate therefore more similar to each other than DZs

  -MZs share 100% of same genes, DZs only 50%

  > suggest OCD has genetic basis