explaining OCD

• what are the two explanations of OCD?

  -genetic

  -neural
• genetic explanations of OCD

  -physical illnesses often have a genetic cause so mental illnesses such as OCD may too
• genetic explanations of OCD - family studies

  -Nestadt = 1st degree relatives had 11.7% probability compared to only 2.7% in a control group (presumably due to shared genes)

  -Miguel = identical twins concordance rate was 53-87%
• genetic explanations of OCD - candidate genes


  =specific genes that influence vulnerability to OCD by influencing neural activity and brain structure
• example of a candidate gene?

  the COMT gene regulates dopamine and one variation of it causes higher levels of dopamine to be released which is more common in people with OCD.
• are dopamine and serotonin hormones or neurotransmitters?

  neurotransmitters
• genetic explanations - supporting evidence for family studies

  -concordance rates are 53-87% which suggests the genetic component is strong but it isnt 100% = other factors

  -diathesis-stress = genes can cause genetic vulnerability but life experiences affect whether OCD actually develops or not
• genetic explanations - supporting evidence for candidate genes

  -Taylor = found as many as 230 candidate genes as OCD is polygenic (caused by multiple genes)

  :( the number of candidate genes reduces usefulness of the genetic explanation - if each gene only has a small influence then its useless in predicting who will be vulnerable to/get OCD
• genetic (+ neural) explanations of OCD - environmental factors

  -could be learning through observation or reinforcement

  e.g. a child observes a parent compulsively washing and the parent encourages the child to do the same
• neural explanations of OCD 


  -focuses on the role of key neurotransmitters and brain structures in causing OCD
• neural explanations of OCD- neurotransmitters

  • serotonin = low levels create repetitive thoughts + obsessions
  • dopamine = high levels can cause compulsive behaviours
• neural explanations of OCD - brain structure

  -a number of brain structures involved in OCD form the worry circuit, normally functions to detect threat, make decisions and get the system back to normal afterwards
• worry curcuit


  -if functioning abnormally:

  • orbifrontal cortex is more active = higher worry signals
  • caudate nucleus fails to suppress these signals and looses control over inner impulses = more frequent + intense obsessions and compulsions are more likely to be acted upon
• neural explanations - supporting evidence for neurotransmitters

  -Pigott = drugs that increase serotonin, decrease OCD symptoms

  -Szechtman = drugs that increase dopamine activity produce repetitive movements in animals

  :( generalizability - animals cant reflect the complexity of OCD

  :) drug treatments - correct the imbalance of serotonin + dopamine
• neural explanations - supporting evidence for brain activity

  -MRI scans show that patients with OCD had higher activity levels in the orbifrontal cortex and the caudate nucleus

  :( doesnt demonstrate cause and effect = could be symptoms rather than causes of OCD