P: The biological approach to explaining OCD Flashcards
(27 cards)
Genetic explanations for OCD?
- Inherited.
- Iindividuals inherited specific genes from their parents and that they are related to the onset of OCD.
What genes may contribute to OCD?
The COMT gene.
The SERT gene.
What is the COMT gene involved in the production of?
catechol-O-methyltransferase, or COMT for short.
An enzyme that breaks down dopamine.
What does COMT regulate the production of?
The neurotransmitter dopamine, that has been implicated in OCD.
- What forms do all genes come in?
- One form of the COMT gene has been found to be more common in who?
- What does this variation produce?
- All genes come in different forms of allelles.
- More common in OCD patients than people without the disorder.
- Produces lower activity of the COMT gene and higher levels of dopamine.
What does the SERT gene affect the transport of & what does it do?
- Transport of serotonin, creating lower levels of this neurotransmitter.
- These lower levels are also implicated in OCD.
The SERT Gene
What did one study find with this gene ?
Found a mutation of this gene in two unrelated families where six of the seven family members had OCD- (Ozaki et al., 2003)
Diathesis- stress
What does this suggest that each individual gene does?
Therefore what does this suggest about the COMT gene or SERT gene?
- Suggests each individual gene only creates a vulnerability (diathesis) for OCD as well as other conditions such as depression.
- Other factors, (stressors) affect what condition develops or indeed whether any mental illness develops.
- Some people could possess the COMT or SERT gene variations but suffer no ill effects.
What is a Concordance rate?
- A measure of genetic similarity.
(e. g. In a sample of 100 twin pairs, one twin of each pair has a phobic disorder. The number of times their other twin also shows the illness determines the concordance rate, so if 40 have phobic disorder, then the concordance rate is 40%.)
What is dopamine?
One of the key neurotransmitters in the brain, with effects on motivation and ‘drive’.
What is a gene?
A part of the chromosome of an organism that carries information in the form of DNA.
What is a neurotransmitter?
Chemical substances that play an important role in the working of the nervous system by transmitting nerve impulses across a synapse.
What levels of dopamine are found to be in people with OCD?
What is this based on?
- Abnormally high!
- Based on animal studies- high doses of drugs that enhance levels of dopamine induce stereotyped movements resembling the compulsive behaviours found in OCD patients.
What levels of serotonin are associated with OCD?
What has this conclusion been based upon?
- Lower levels of serotonin.
- Based on the fact that antidepressant drugs that increase serotonin activity have been shown to reduce the OCD symptoms (Pigott et al., 1990) whereas antidepressants that have less effect on serotonin do not reduce OCD symptoms (Jenicke, 1992).
Abnormal brain circuits
What areas of the brain are thought to be abnormal in people with OCD?
Several areas in the frontal lobes.
Abnormal brain circuits.
Where is the caudate nucleus located and what does this normally do?
In turn, what happens?
- Located in the basal ganglia- normally supresses signals from the orbitofrontal cortex (OFC).
- In turn, the OFC sends signals to the thalamus about things that are worrying such as a potential germ hazard.
Abnormal brain circuits
What happens when the caudate nucleus is damaged?
It fails to suppress minor ‘worry’ signals and the thalamus is alerted, which in turn sends signals back to the OFC, acting as a worry circuit.
Abnormal brain circuits
What is this supported by?
Supported by PET scans of patients with OCD, taken while their symptoms are active (e.g. when a person with a germ obsession holds a dirty cloth). Such scans show heightened activity in the OFC.
Abnormal brain circuits
What does Comer (1998) report that serotonin plays a key role in?
What is dopamine linked to?
- Key role in the operation of the OFC and the caudate nuclei, and it would therefore appear that abnormal levels of serotonin might cause these areas to malfunction.
- Dopamine- linked to this system, as it is the main neurotransmitter of the basal ganglia. High levels of dopamine lead to overactivity of this region (Sukel, 2007).
What is the OFC?
Orbitofrontal cortex
Write a PEEL paragraph discussing the research support for genes and OFC:
P - Research support for genes and OFC
E - Studies demonstrate the genetic link to abnormal levels of neurotransmitters.
E - 2007 study used MRI to produce images of brian activity in OCD patients and their immediate family members without OCD and also a group of unrelated healthy individuals.
E - OCD patients and close relatives had reduced grey matter in key regions of the brain.
L - Supports view that anatomical differences are inherited and these may lead to OCD in certain individuals - some are saying perhaps in the future MRI scans may be used to detect OCD risk.
Write a PEEL paragraph discussing the alternative explanations for OCD:
P - Biological approach faces strong competition from psychologcial explanations.
E - Two-process model can be applied to OCD - intial learning occurs when NS (eg dirt) is associated with anxiety. Association is maintained due to anxiety-provoking stimulus being avoided. An obession is formed and a link is learned with compulsive behaviours (eg hand-washing) that appear to reduce anxiety.
E - This explanation is supported by success of ERP treatments for OCD. Reportedly have high success rates - 1998 study reported 60-90% adults with OCD improved with ERP.
L - Suggest OCD cannot just be explained by biological approach - it may have psychological causes too.
What is ERP?
Exposure and response prevention - form of treating OCD similar to systematic desensitisation.
How does ERP work?
- Patients experience feared stimulus.
- At the same time are prevented from performing their compulsive behaviour.
- Learn that anxiety levels out - cannot increase indefinately.
