Biological approach to explaining OCD Flashcards
What are the two biological explanations for OCD?
Genetic and neural explanations
What are candidate genes?
Genes which create vulnerability for a specific disorder
What are the two candidate genes for OCD?
- Allele of the COMT gene – increase in dopamine
- SERT gene – effects transport of serotonin which causes a decrease in serotonin
How does an allele of the COMT gene lead to an increase in dopamine?
-Produces less COMT, which regulates dopamine
-Leads to increase in dopamine as it is not being regulated
Which two neurotransmitters have been implicated in OCD?
- Dopamine – levels are too high in people with OCD
- Serotonin – levels are too low in people with OC
What are two neural explanations for OCD?
- Influence of neurotransmitters
- Abnormal brain circuits – the ‘worry circuit’
What is the ‘worry circuit’ in the brain?
-Orbitofrontal cortex (OFC) sends ‘worry signals’ to the thalamus
-These are normally suppressed by the caudate nucleus
-People with OCD tend to have a damaged caudate nucleus, which results in the thalamus being alerted and confirming the ‘worry’ to the OFC
What are the two strengths of the biological approach to explaining OCD?
Evidence for genetic basis- family and twin studies- Family study: Marini and Stebnicki (2012)à 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 à that the serotonin system is involved in OCD. Menzies et al. (2007)- used MRI to measure brain activity in OCD patients and their immediate family members without OCD and also a group of unrelated healthy people. OCD patients and their close relatives had reduced grey matter in key regions of the brain à supports the view that anatomical differences are inherited and these may lead to OCD.
Counter- Hard to establish a cause and effect relationship- these biological abnormalities could be a result of OCD rather than it’s cause.
What are the two limitations of the biological approach in explaining OCD?
No unique neural system: The serotonin-OCD link may not be unique 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.
Alternative explanations: Psychological explanations can be used to explain and treat OCD. 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.
