biological explanations for ocd

Question 1

What are the two explanations for OCD?

Answer 1

Genetic

Neural

Question 2

Describe Lewis’ gene research

Answer 2

37% OCD patients had parents with OCD
21% had siblings
Genetic vulnerability passed on

Question 3

What is the diathesis stress model?

Answer 3

Genes leave people more likely to suffer OCD

Environmental stress triggers condition

Question 4

What are candidate genes?

Answer 4

Genes that create OCD vulnerability
Involved in regulating serotonin system
5HT1-D Beta

Question 5

How is OCD polygenic?

Answer 5

Several genes involved
Taylor - 230 different genes
Involved in serotonin and dopamine

Question 6

How is OCD aetiologically heterogeneous?

Answer 6

Origin of OCD has different causes
One group of genes causes OCD in one person but different group in another
Different types of OCD related to different groups of genes

Question 7

Genetic evaluation - supportive evidence

Answer 7

Twin studies
Nestadt - 68% of identical twins shared OCD
31% non identical twins

Question 8

Genetic evaluation - too many candidate genes

Answer 8

Hard to know all genes involved
Many genes
Not very useful - little predictive value

Question 9

Genetic evaluation - environmental risk factors

Answer 9

Cromer - over half OCD patients had traumatic past event
OCD more severe in those with multiple traumas
Not entirely genetic

Question 10

How does serotonin affect OCD?

Answer 10

Regulates mood
Neurotransmitters relay info from one neuron to another
Low serotonin - transmission of mood relevant info is abnormal
Explains some OCD

Question 11

How is OCD related to decision making systems in the brain?

Answer 11

OCD - impaired decision making
Abnormal functioning of lateral of frontal lobes
Frontal lobes responsible for logic
Left parahippocampul gyrus function abnormally - associated with processing unpleasant emotions

Question 12

Neural evaluation - supporting evaluation

Answer 12

Some antidepressants target serotonin system

Reduce OCD

Question 13

Neural evaluation - not clear what neural mechanisms are involved

Answer 13

Decision making systems are the ones that function abnormally in OCD
Research identified other systems that are involved sometimes
No system that always plays a role

Question 14

Neural evaluation - should not assume neural mechanisms cause OCD

Answer 14

Biological abnormalities may be a result of OCD instead

Question 15

Neural evaluation - serotonin link may be comorbidity with depression

Answer 15

OCD sufferers often have depression
Depression involves serotonin system
Comorbidity not OCD

Question 16

Genetic evaluation - twin studies flawed

Answer 16

Identical twins also more similar in terms of environment

This may account for greater likelihood of sharing OCD than non identical twins