biological explanation

• what is the genetic explanation?

  Suggest OCD is cause by a combination of genetics
• What is the diathesis-stress model?


  suggests that certain genes make you more likely to develop a mental disorder but environmental stress is necessary to trigger the condition
• define "gene"

  A part of the chromosome of an organism that carries info in the form of DNA
• What is dopamine?

  a neurotransmitter in the brain, with effects on motivation and drive
• what is a candidate gene?


  a gene that is thought to be linked to a specific trait (creates a vulnerability of developing a disorder)
• name a candidate gene involved in OCD

  SERT gene
• What is the SERT gene?

  Helps to control the transportation of serotonin. If the SERT gene is too active, then there is too much of the protein that SERT produces, meaning their is less serotonin. Low levels of serotonin have been linked to OCD
• What is the key supporting study for the genetic explanation?

  Lewis (1936)
• What did Lewis (1936) find?

  37% of his patients had parents with OCD & 21% had siblings with OCD
• what are the two main types of twin studies used to study the genetic influence on OCD?

  - Separated at birth twins

  - Identical & non-identical twins
• How are separated twins used?

  Are compared with twins who grow up in the same environment as each other to see if separated twins growing up in different environments are just as likely to both have OCD as twins who share the same environment
• Why is this twin study used less nowadays?

  Because finding separated twins is becoming rarer
• What is the key study related to MZ & DZ twins?

  Nestadt (2010)
• What did Nestadt do & find?

  Found 68% of MZ twins shared OCD whereas 31% of DZ twins shared OCD
• What are the weaknesses of twin studies within OCD?

  - It can be questioned if identical & non-identical twins share equally similar environments

  - Some argue genes and environment work separately
• What can OCD be described as?

  Polygenic
• define polygenic

  A condition influenced by many different genes
• What is a key study linking to OCD being polygenic?

  Taylor (2013)
• what did Taylor (2013) do & find?

  Found up to 230 different genes may be involved with OCD
• Define co-morbidity


  Medical condition that coexists with another
• What are the 2 key genes associated with OCD?

  COMT & SERT genes (regulate dopamine & serotonin)
• EVALUATION OF BIOLOGICAL EXPLANATION:
• Give the strengths

  - Good supporting evidence that some people may acquire OCD due to their genetic makeup
• What is the evidence used for "good supporting evidence"

  Nestadt (2010)
• Give the weaknesses

  - Too many candidate genes involved with OCD

  - Twin studies are flawed as genetic evidence
• Expand on "too many candidate genes"

  These genes only increase the risk of OCD by a fraction. So genetic ex has little predictive value so not useful
• Expand on "twin studies are flawed in genetic evidence"

  MZ twins have identical upbringing whereas DZ upbringing is varied. This affects validity of findings due to varying environments & experiences