9. Biological Approach To Explaining OCD Flashcards
What is a genetic explanation?
Genes passed down by parents are the cause of OCD
Who did Lewis observe in 1936?
OCD patients and their family members
What percentage of Lewis’ patients had parents with OCD?
37%
What percentage of Lewis’ patients had siblings with OCD?
21%
What is likely passed down through the genes rather than genetic certainty?
Genetic vulnerability
What does the diathesis-stress model say?
Certain genes leave people more likely to suffer a mental disorder, but it is not certain
What are candidate genes?
Genes that create vulnerability for OCD
What are some OCD candidate genes involved in?
Regulation of the serotonin system
What gene is thought to affect the transport of serotonin across synapses?
5HT1-D beta
What does polygenic mean?
Many genes influence a trait
How many genes did Taylor find in 2013 could be linked to OCD?
230
What two neurotransmitters are most believed to be associated with OCD?
Serotonin, dopamine
What does aetiologically heterogenous mean?
The genes that cause OCD are different from person to person
What types of OCD are most likely the result of particular genetic variations?
Hoarding disorder, religious obsession
What did Nestadt et al study in 2010?
Twin studies relating to OCD
In Nestadt et Al’s study, what percentage of identical twins shared OCD?
68%
In Nestadt et Al’s study, what percentage of non-identical twins shared OCD?
31%
What did Cromer et al find in 2007 about the past of OCD patients?
Over half had a traumatic event in their past, and OCD was more severe in those who had more than one trauma
What are neurotransmitters responsible for?
Relaying information between neurons
What are neural explanations?
OCD is determined by the behaviour of the nervous system, including the brain and neurotransmitters
What happens if someone has low levels of serotonin?
Their mood is affected
What neurotransmitter abnormality can sometimes explain OCD?
Serotonin
What do some cases of OCD, in particular hoarding disorder, seem to be associated with?
Impaired decision making
What part of the brain can impaired decision making be associated with?
The lateral frontal lobes
What are the lateral frontal lobes responsible for?
Logical thinking and decision making
What other part of the brain functions abnormally in OCD?
Parahippocampal gyrus
What is the parahippocampal gyrus associated with?
Processing unpleasant emotions
What drug treatment can be given to reduce symptoms of OCD?
Antidepressants
Why does the effectiveness of antidepressants show that OCD can be related to the serotonin system?
Antidepressants work purely on the serotonin system
What is the issue with using brain systems to identify OCD?
No system has been found that always plays a role in OCD
Why should we not argue neurotransmitter or brain structure abnormalities cause OCD?
They may be the result, rather than the cause
What other mental disorder do people with OCD usually face?
Depression
What is co-morbidity?
Having two mental disorders together
Why is accompanying depression an issue for explaining OCD?
The disruption to the serotonin system may be from depression, rather than OCD
Why are twin studies flawed as genetic evidence?
As well as having shared genes identical twins are likely to have a more similar environment than non-identical twins
Why might non-identical twins not have the same environment?
They could be opposite genders, which leads to different life experiences
What are the 3 aspects of the genetic explanation of OCD
- candidate genes
- OCD is polygenic
- there are different types of OCD
What is an example of a candidate gene for OCD
5HT1-D, which is implicated in the efficiency of transport of serotonin across synapses
Two weaknesses of genetic explanation
- too many candidate genes
- environmental risk factors
Too many candidate genes
- psychologists have been largely unsuccessful at pining down all of the genes involved in OCD
- this is largely because there are several genes involved, and each genetic variation increases risk by only a fraction
- so the genetic explanation is unlikely to ever be very useful because it provides very little predictive value
environmental risk factors
- environmental factors can also trigger OCD (diathesis risk model)
- so OCD can not be entirely genetic in origin, at least not in all cases
- it may be more productive to focus on the environmental causes because we are more able to do something about these
An example of environmental stress causing OCD
- Cromer eat al
Found that over half of the OCD patients in their sample had a traumatic event in their lives, and the OCD was more severe in those with more than one trauma
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 individual neurons.
Role of serotonin
a neurotransmitter believed to help regulate mood
A strength of neural explanations of OCD
- supporting evidence
- some antidepressants which work purely on the serotonin system by increasing levels, have effectively reduced OCD symptoms
- OCD symptoms also form part of other biological originated conditions like Parkinson’s disease, suggesting biological processes that cause symptoms in those conditions may also be responsible for OCD
3 weaknesses of the biological approach to explaining OCD
- it is not clear exactly what neural mechanisms are involved
- we should not assume that the neural mechanisms cause OCD
- the serotonin ocd link may simply be co morbidity with depression
It is not clear exactly what neural mechanisms are involved
- cavedini et als study has shown that these neural systems are the same systems that function abnormally in OCD
- but, research has also identified other brain systems that may be involved sometimes, but no system has been found that always plays a role in OCD
So we can’t really claim to understand the neural mechanisms involved in OCD
We should not assume the neural mechanisms cause OCD
There is evidence suggesting that various neurotransmitters and brain structures function abnormally in OCD patients, but we can’t be sure that these cause it- they could develop because of it
The serotonin-ocd link may simply be co morbidity with depression
- many ocd sufferers also become depressed (co-morbidity)
- this depression likely involves disruption to the serotonin system
- so we can’t be sure that serotonin disruption is involved with OCD: it may be that the serotonin system is simply disrupted because the patient is depressed as well
