Lesson 12: Biological Explanations for OCD

Question 1

What does polygenic mean?

Answer 1

When more than one gene is responsible for a disorder.

Question 2

How many genes are thought to be responsible for OCD?

Answer 2

230

Question 3

Genes that might be responsible for OCD are called?

Answer 3

Candidate genes

Question 4

What is a neurotransmitter?

Answer 4

Chemical messengers that transmit messages between neurons.

Question 5

High levels of what neurotransmitter is associated with OCD?

Answer 5

Dopamine

Question 6

What does the COMT gene do?

Answer 6

Regulates the production of dopamine

Question 7

Low levels of what neurotransmitter is associated with OCD?

Answer 7

Serotonin

Question 8

What does the SERT gene do?

Answer 8

Affects the transportation of serotonin

Question 9

Evaluation of Genetic Explanations?

Answer 9

+ Nestadt (2000) supports the genetic explanation for OCD. He found that people who had a first-degree relative who already had OCD were five times more likely to also get the disorder.

+ Billett (1998) supports the idea that OCD is transmitted genetically. He found from a meta-analysis of 14 twin studies that OCD is twice as likely to be concordant (inheriting the same disorder) in identical (monozygotic) twins compared with non-identical (dizygotic) twins.

• A criticism of the genetic explanation is that the concordance rate for OCD in identical twins is not 100%. Therefore OCD cannot be caused entirely by genetic factors.

Question 10

What does high levels of dopamine affect?

Answer 10

Affects the levels of activity in the basal ganglia of the brain (hyperactivity) and causes repetitive motor functions (compulsions)

Question 11

What does low levels of serotonin affect?

Answer 11

Affects the caudate nucleus of the basal ganglia and causes it to malfunction, resulting in obsessions

Question 12

Evaluation of Neural Explanations?

Answer 12

+ Anti-depressant drugs increase serotonin levels in OCD patients, and this has lead to a reduction in OCD symptoms. Therefore there is good evidence to suggest that low levels of serotonin could be a cause for OCD.

• A disadvantage of the neural explanations of OCD is that neurotransmitters such as dopamine and serotonin might not necessarily cause OCD. Instead low levels of serotonin and high levels of dopamine might be a symptom of OCD.