Biological Approach To Explaining OCD Flashcards
State the two biological explanations for OCD.
- Genetic explanations 2. Neural (brain) explanations.
What are candidate genes? What are the two candidate genes for OCD?
Genes which create vulnerability for a specific disorder.
1. Allele of the COMT gene
2. SERT gene.
2 Strengths(1 counter) for the biological approach to explaining OCD
Evidence for genetic basis- family and twin studies:
Family study: Marini and Stebnicki (2012) A person with a family member diagnosed with OCD is four times as likely
to develop it as someone without.
Twin study: Nestadt et al. (2010)à reviewed twin studies and found that 68% of monozygotic twins shared OCD as opposed to 31% of non-identical twins.
COUNTER - Twin studies make the incorrect assumption that MZ twins are only more similar than DZ twins in terms of their genes - overlook the fact that MZ twins may also be more similar in terms of shared environments. E.g. DZ twins might be a boy and a girl who have quite different experiences and it could be these experiences that make DZ twins less similar than MZ twins rather than their genes.
Evidence for neural basis:
There is evidence to support the role of neurotransmitters in OCD. Some antidepressants work to increase the levels of serotonin and these drugs have been found to reduce the symptoms of OCD.
Soomro et al. (2009) reviewed 17 studies comparing SSRIs to placebos in the treatment of OCD. Found that SSRIs to be more effective than placebos in reducing the symptoms of OCD up to 3 months after treatment.
How does an allele of the COMT gene is implicated in OCD
The allele produces less COMT. COMT regulates dopamine. This results in increased levels of dopamine, which is associated with compulsions, as it is not regulated.
Explain how the SERT gene is implicated in OCD.
SERT gene affects the transport of serotonin, causing a decrease in serotonin levels. Serotonin levels are too low in people with OCD.
What are two neural explanations for OCD?
- Influence of neurotransmitters 2. Abnormal brain circuits.
Outline two neurotransmitters that have been implicated in OCD.
- Dopamine – levels are too high in people with OCD
- Serotonin – levels are too low in people with OCD.
Outline how serotonin and dopamine are implicated in OCD.
Decreased levels of serotonin lead to obsessive thoughts and anxiety.
Increased/excessive levels of dopamine lead to compulsive behaviour.
What is the ‘worry circuit’?
Orbitofrontal cortex (OFC) sends “worry signals” to the thalamus. These signals are usually supressed by the caudate nucleus. People with OCD tend to have a damaged caudate nucleus as they have abnormal levels of serotonin. This means the caudate nucleus does not supress the worry signals so the thalamus is alerted and confirms the worry to the OFC.
2 Limitations for the biological approach to explaining OCD
Alternative explanations:
The two-process model can be used to explain OCD.
Classical conditioning= learning occurs when a neutral stimulus (dirt) is associated with an unconditioned stimulus (germs) producing anxiety.
Operant conditioning= This association is maintained because the anxiety-provoking stimulus is avoided and they receive negative reinforcement. An obsession is formed and a link is learned with compulsive behaviours (hand-washing) that appear to reduce anxiety.
A treatment called exposure and response prevention (ERP) has been developed based on the behaviourist two-process model. Patients have to experience their feared stimulus and stop performing their compulsive behaviour. Studies have supported a high success rate for people with OCD.
Serotonin not relevant to OCD:
Many people with OCD also experience clinical depression- this is known as co-morbidity (having two disorders together). This depression probably involves disruption to action of serotonin. This suggests that it could simply be that serotonin activity is disrupted in many people with OCD because they are depressed as well and so serotonin may not be relevant to OCD symptoms.
