The biological approach to explaining OCD Flashcards
What are the 2 types of OCD explanation?
Neural and genetic
What 2 genes may contribute to OCD?
The COMT gene and the SERT gene
What does the COMT gene do?
Regulates the production of a neurotransmitter called dopamine
What is a neurotransmitter?
A chemical substance that transmits nerve impulses across a synapse
What is dopamine?
A neurotransmitter involved with motivation and ‘drive’
How is the COMT gene linked to OCD?
One allele of the gene is more common in OCD patients than people without the disorder
How does the OCD variation of the COMT gene lead to OCD symptoms?
It produces lower activity of the COMT gene and higher levels of dopamine
What does the SERT gene do?
Affects the transportation of serotonin
What does SERT do to serotonin levels?
Decreases them
What did a study regarding the SERT gene find?
In two unrelated families who had a mutated SERT gene, 6 of the 7 family members had OCD
In OCD patients, what are dopamine levels expected to be?
Higher than normal
What did animal studies find about dopamine?
High doses of drugs that enhance dopamine levels induce stereotyped movements resembling the compulsions of OCD patients
What is the name of the brain circuit associated with OCD?
The worry circuit
What are the 3 brain structures involved in the worry circuit?
The caudate nucleus, the OFC and the thalamus
What does the caudate nucleus do in an individual without OCD?
Supresses signals from the orbitofrontal cortex
What does the caudate nucleus do in an individual with OCD?
Fails to supress minor ‘worry’ signals
What does the orbitofrontal cortex do?
Sends signals to the thalamus about things that are worrying
What support is there for the worry circuit?
PET scans taken while OCD symptoms were active found heightened activity in the OFC
Which neurotransmitters are involved in the worry circuit?
Dopamine and serotonin
What are the 4 AO3 points of the biological explanation of OCD?
1) Family + twin studies
2) Alternative explanations
3) Research support for genes and OFC
4) Tourette’s syndrome
In the first degree relative study into OCD, how many OCD participants were there?
80
In the first degree relative study into OCD, how many relatives of OCD participants were there?
343
In the first degree relative study into OCD, how many non-OCD participants were there?
73
In the first degree relative study into OCD, how many relatives of the non-OCD participants were there?
300
In the first degree relative study into OCD, what was found about the people who had a first-degree relative with OCD?
They were 5x more likely to develop OCD at some point in their life
What did a twin study meta analysis find about OCD?
MZ twins were twice as likely to develop OCD if their co-twin had it, compared to DZ twins
What type of explanation challenges the biological explanation of OCD?
Psychological explanations
Which psychological model can be applied to the explanation of OCD?
Mowrer’s two process model
How can the two process model be applied to OCD?
A neutral stimulus is associated with anxiety - the association is maintained as the anxiety-inducing stimulus is avoided - this leads to the development of an obsession
How can the diathesis stress model be applied to OCD?
OCD manifests in genetically vulnerable individuals after an activating event that triggers the responsible genes
In the study that supports the role of genes + the OFC, who was in the experimental group?
People with OCD and their immediate family members who didn’t have OCD
In the study that supports the role of genes + the OFC, who was in the control group?
Individuals without OCD who were unrelated to the experimental group
In the study that supports the role of genes + the OFC, what were the findings?
The OCD patients and their relatives had reduced grey matter in key regions of the brain, including the OFC
What did researchers find about Tourette’s syndrome in relation to OCD?
That OCD is one form of expression of the same gene that determines Tourette’s
For which other disorders are the obsessions observed in OCD and Tourette’s patients also observed? (2)
Anorexia nervosa and autism
