Biological approach to explaining OCD

Question 1

What are the two biological explanations for OCD?

Answer 1

• genetic
• neural

Question 2

What did Lewis find in his study about genes and vulnerability for OCD?

Answer 2

• genes involved in vulnerability to OCD
• observed OCD patients
• 37% had parents with OCD and
  21% had siblings with OCD
• suggest OCD runs in the family
• what is passed on is genetic vulnerability for OCD

Question 3

What does the diathesis stress model argue?

Answer 3

• certain genes leave some people more likely to develop a mental disorder but it is not certain
• environmental stressor necessary to trigger conditions e.g. bereavement

Question 4

What are candidate genes and give examples? genetic explanation

Answer 4

• genes identified by researchers which create a vulnerability for OCD
• SERT gene which regulates the neurotransmitter serotonin
• COMT regulates the production of the neurotransmitter dopamine that has been implicated in OCD.

Question 5

What is meant by OCD being polygenic? genetic explanation

Answer 5

• OCD is not caused by one single gene but by a combination of genetic variations =increase vulnerability
• Taylor > analysed findings from previous studies and found evidence that up to 230 different genes may be involved in OCD

Question 6

What is meant by there are different types of OCD in people?

Answer 6

• One group of genes may cause OCD in one person while another group of genes may cause disorder in another person > OCD is aetiologically heterogeneous
• different types of OCD may also be the result of particular genetic variations e.g. hoarding disorder and religious obsession

Question 7

What is the neural explanation?

Answer 7

• Explanation that focuses on the nervous system and structures in the brain

Question 8

What is the role of serotonin in OCD?

Answer 8

• one explanation of OCD is the role of serotonin
• helps to regulate mood
• if the neurotransmitter serotonin is low then normal transmission of mood-relevant information does not take place & a person may experience low moods

Question 9

What is the role of decision making systems in OCD?

Answer 9

• some case of OCD
• hoarding disorder = associated with abnormal functioning of the lateral frontal lobes (associated with logical thinking)
• left parahippocampal gyrus (associated with processing unpleasant emotions) functions abnormally in OCD

Question 10

What support is there for the genetic explanation?

Answer 10

• Nestadt et al > reviewed twin studies & found that 68% of MZ twins shared OCD as opposed to 31% of DZ twins
  Counterpoint - concordance not 100%, other factors
• Marini & Stebnicki found that a person with a family diagnosed with OCD is 4x more likely to develop compared to someone without
• increase validity

Question 11

What is a limitation of the genetic explanation for OCD?

Answer 11

• there are also environmental risk factors
• OCD is not entirely genetic in origins>
  environmental factors may also trigger or increase risk of developing OCD
• Cromer found that over 1/2 of the OCD clients in their sample had experienced a traumatic event in their past & OCD more severe in those with one or more traumas

Question 12

What research support is there for the neural explanation?

Answer 12

• Antidepressants that work purely on serotonin are effective in reducing OCD symptoms
• Soomro et al found that 70% of his patients symptoms were reduced when taking SSRI’s
• suggest serotonin plays role & biological process implicated in OCD

Question 13

What is a limitation of the neural explanation?

Answer 13

• serotonin-OCD link many not be unique to OCD
• many people with OCD also experience clinical depression =co-morbidity
• depression possibly caused by disruption to action of serotonin
• thus it could simply be that serotonin activity may be disrupted because those with OCD are depressed as well
• serotonin not relevant to OCD symptons