Lesson 12 - Biological Explanations of OCD

Question 1

The Biological Approach of Explaining OCD

Answer 1

Assumes OCD is caused by genetic and biochemical factors

Question 2

Genetic Explanations

Answer 2

OCD has been classed as polygenic
One single gene is not responsible for the disorder
Instead as many as 230 genes may be responsible
Candidate genes
COMT gene regulates production of a neurotransmitter called dopamine which in high levels is associated with OCD
One variation of COMT results in higher levels of dopamine - more common in OCD patients
SERT gene affects transportation of serotonin, significantly reducing it - OCD and depression association

Question 3

Genetic Explanations of OCD Evaluation
Nestadt (2000)
Positive

Answer 3

Found that people who had a first degree relative who already had OCD were 5 times more likely to also get the disorder

Question 4

Genetic Explanations of OCD Evaluation
Billett (1998)
Positive

Answer 4

Found from a meta-analysis of 14 twin studies that OCD is twice as likely to be concordant incidental twins compared with non-identical twins

Question 5

Genetic Explanations of OCD Evaluation
Concordance Rate
Negative

Answer 5

Concordance rate for OCD in identical twins is not 100%

OCD cannot be caused entirely by genetic factors

Question 6

Neural Explanations for OCD

Answer 6

Dopamine and serotonin are neurotransmitters that affect mood
Abnormal levels of these are associated with abnormal transmission of mood-related information
OCD sufferers have high levels of dopamine which has been linked to hyperactivity in the basal ganglia area in the brain causing repetitive motor functions
Serotonin plays a role in operating caudate nucleus in the basal ganglia of the brain and low levels cause caudate nucleus to malfunction and result in obsessions

Question 7

Neural Explanations for OCD Evaluation
Anti-Depressants
Positive

Answer 7

Anti-depressant drugs increase serotonin levels in OCD patients
Leads to reduction in OCD symptoms
Suggests low levels of serotonin could be a cause for OCD

Question 8

Neural Explanations for OCD Evaluation
Neurotransmitters
Negative

Answer 8

Dopamine and serotonin might not necessarily cause OCD

Low levels of serotonin and high levels of dopamine might be a symptom of OCD