Psychopathology - the biological approach to explaining OCD

Question 1

Genetic: What did Nestadt et al (2000) find out about OCD?

Answer 1

Reviewed twin studies and found that 68% of identical twins shared OCD as opposed to 3% of non-identical twins

Question 2

Genetic: Why does this suggest OCD is only partly genetic?

Answer 2

Suggests strong genetic component - monozygotic twins who share 100% DNA more likely to both develop OCD than dizygotic twins who only share 50% but not 100% of identical both had depression so not fully genetic

Question 3

Genetic: How many candidate genes are there for OCD?

Answer 3

230 but currently 2 main possibilities:
COMT gene
SERT gene
Genes are part of the cause of OCD, researchers are unsure which genes are important

Question 4

Genetic: What is meant by polygenic?

Answer 4

More than one gene is involved

Question 5

Genetic: What does it mean that OCD is etiologically heterogenous?

Answer 5

Different combinations of genes cause different types of OCD in different people

Question 6

Genetic: How could a mutation of the COMT gene cause OCD?

Answer 6

Causes low levels of COMT enzyme. This enzyme breaks down dopamine (neurotransmitter) in the brain. So low levels of COMT mean high levels of dopamine

Question 7

Genetic: How could a mutation of the SERT gene cause OCD?

Answer 7

Causes high levels of a protein which removes serotonin. So high levels of protein mean low levels of serotonin

Question 8

Genetic: What is the Interactionist approach of OCD, using the diathesis stress model as an example?

Answer 8

Suggests certain genes create a vulnerability for a disorder but without a stressor the disorder won’t develop
Diathesis + Stress = Disorder

Question 9

Neural: How is serotonin associated with OCD?

Answer 9

People with OCD thought to have low levels of serotonin - the brain doesn’t communicate info about mood effectively and is associated with the symptom of anxiety

Question 10

Neural: How is dopamine associated with OCD?

Answer 10

People with OCD thought to have high levels of dopamine which is important for maintaining interest and motivation - high levels associated with symptoms of compulsions and obsessions in OCD

Question 11

Neural: What regions of the brain are involved in the worry circuit?

Answer 11

Orbitofrontal cortex (OFC) and caudate nucleus appear to have a role in OCD’s development

Question 12

Neural: What is the worry circuit and how is it linked to OCD?

Answer 12

OFC responsible for sending worry signals, picked up to the thalamus in the center of the brain
Caudate nucleus responsible for suppressing some of these unimportant worry signals

Question 13

Neural: What symptoms of OCD does this link to?

Answer 13

In patients, thought that caudate nucleus isn’t working properly so worry signals don’t get suppressed and too many alert the thalamus which causes symptom of anxiety