Biological explanation of OCD PPO Flashcards
biological approach
a perspective that emphasises the importance of physical processes in the body such as genetic inheritance and neural function
genetic explanation
genes make up chromosomes and consist of DNA which codes the physical features of an organism and psychological features
Lewis observed that 37% of his OCD patients had a parent with OCD and 21% had siblings with OCD. Thus suggesting that OCD runs in families but genetic vulnerability is probably what is actually passed on not OCD specifically.
neural explanations
the view that physical and psychological characteristics are determined by the behaviour of the nervous system, in particular the brain as well as the individual neurons
diathesis-stress model
explains that specific genes lead people more likely to develop a mental disorder but it isn’t proven. Yet environmental stress is required to trigger the condition.
candidate genes
- Identified genes which create vulnerability for OCD
- Some involved in regulating development of serotonin system
- 5HT1-D beta is used in the transportation of serotonin across synapses
OCD is polygenic
OCD is not caused by one gene but a combination of variations
Taylor analysed findings of previous studies and found that 230 different genes may be involved in OCD
Including those associated with dopamine and serotonin, both neurotransmitters who regulate mood
Different types of OCD
- One group of genes may cause OCD in one person but not another
- Aetiologically heterogeneous (the origins of CCD vary from one person to another)
- Different types of OCD may be because of particular gene variations eg hoarding disorder and religious obsession
the role of serotonin
- Helps regulate mood
- Neurotransmitters relay information from one neuron to another
- Low levels of serotonin means low moods
- Some cases of OCD explained by reduction in functioning of serotonin system of the brain
decision-making systems
- Some cases (mainly hoarding disorder) is associated with impaired decision-making
- To do with abnormal functioning of the lateral of the frontal lobes
- Frontal lobes responsible for logical thinking and making decisions
- Left parahippocampal gyrus associated with unpleasant emotions
research support for genetic explanations
strength
Strong evidence base
* Twin studies from Nestadt et al found 68% of identical twins (MZ) shared OCD but only 31% of non-identical twins (DZ)
* Family studies found that is a family member has OCD you are 4 times as likely to develop the condition (Marini and Stebnicki)
* Must be some genetic influence on the development of OCD.
environmental risk factors of genetic explanations
limitation
Ignores environmental risk factors
* Environmental risk factors trigger or increase the risk of developing OCD
* Cromer et al found over half of her OCD clients had experienced traumatic events before and the OCD got more severe in those with worse trauma
Genetic vulnerability only provides a partial explanation.
animal studies
genetic explanation
Evidence from animal studies show certain genes are responsible for repetitive behaviour eg mice (Ahmari)
Mice and humans are not similar so would be difficult to generalise
research support for neural explanations
strength
Existence of supporting evidence
* Antidepressants working only on serotonin are effective in the reduction of OCD symptoms
* Serotonin may be involved in OCD
* Parkinson’s disease is formed from OCD symptoms (Nestadt et al)
Biological processes underlie OCD
no unique neural system
limitation
The serotonin to OCD link may not be special to OCD
* Many OCD sufferers also experience clinical depression
* Co-morbidity is having two disorders together
* Depression probably disrupts the action of serotonin
Serotonin may not be relevant to OCD symptoms
