9. The Biological Approach To Explaining OCD Flashcards
What is the genetic explanation for why a person develops OCD?
The genetic explanation suggests that whether a person develops OCD is at least partly due to their genes. There is a suggestion that OCD runs in families and that what it passed on is a genetic vulnerability to develop the disorder.
What are candidate genes?
Genes which create a vulnerability for OCD. Some of these genes are involved in regulating the serotonin system. For example, the gene 5HT1-D beta is thought to play a role in how efficiently serotonin travels across synapses.
However, like many conditions, OCD seems to be polygenic. What does this mean? Is there any reason for this?
Polygenic means that OCD isn’t caused by a single gene but by several. There is evidence to suggest there is up to 230 different genes that may be involved in OCD.
Most anxiety disorders respond to a wide range of drugs but OCD seems only to respond to those drugs that affect serotonin (a neurotransmitter in the brain). What does this suggest about OCD?
This suggests that OCD is related to low levels of serotonin.
What are the consequences of having low levels of serotonin?
If a person has low levels of serotonin then normal transmission of mood-related information does not take place and mood (and sometimes other mental processes are affected).
How so drugs which increase the amount of serotonin in the brain provide support for the theory?
Drugs which increase the amount of serotonin in the brain, such as SSRI anti-depressants, also reduce the OCD symptoms, providing support for the theory that low levels of serotonin may be responsible for OCD.
Dopamine levels are thought to be abnormally high in people with OCD. How do we know this?
This is based on animal studies in which high doses of drugs that enhanced levels of dopamine were given to animals and induced stereotyped movement resembling the compulsive behaviours found in OCD patients.
How can parts of the brain be associated with OCD?
Some case of OCD, and in particular hoarding disorder, seem to be associated with impaired decision making. This may in turn be associated with abnormal functioning of the lateral (side bits) of the frontal lobes of the brain.
The frontal lobes are the front part of the brain responsible for logical thinking and making decisions.
There is also evidence to suggest that an areas called the left parahippocampal gyrus associated with unpleasant emotions, functions abnormally in OCD.
EVALUATION OF THE GENETIC EXPLANATION
Give one strength of the genetic explanation of OCD
There is supporting evidence that some people are vulnerable to OCD as a result of their genetic make-up. Twin studies provide good evidence for the effects of genes.
Nestadt et al reviewed previous twin studies and found that 68% of identical twins shared OCD as opposed to 31% of non-identical twins.
This strongly supports a genetic influence on OCD.
EVALUATION OF THE GENETIC EXPLANATION
Outline the three limitation of the genetic explanation for OCD
- twin studies are flawed as genetic evidence
- a limitation is that it is not just genes, environmental risk factors are also involved
- too many candidate genes have been found
EVALUATION OF THE GENETIC EXPLANATION
Explain why twin studies are flawed as genetic evidence
Twin studies are a standard source of evidence for genetic influence. However, they make the assumption that identical twins are more similar than non-identical twins in terms of their genes, but overlook the fact that identical twins may also be more similar in terms of shared environments (for example, non-identical twins might be a boy and a girl who have quite different experiences).
This is a weakness of using twin studies to investigate the genetic basis of behaviour.
EVALUATION OF THE GENETIC EXPLANATION
Explain the limitation in that it is not just genes, environmental risk factors are also involved
It seems that environmental risk factors can also trigger OCD. For example, studies have found that over half the OCD patients in their sample had a traumatic event in their past, and OCD was more severe in those with one or more traumas.
This suggests that OCD cannot be entirely genetic in origin, at least not in all cases. The fact that the concordance rate for identical twins is not 100% further supports the idea that there must be some environmental influence upon the disorder.
EVALUATION OF THE GENETIC EXPLANATION
Explain the limitation of too many candidate genes being found
Even though the research evidence suggests that OCD is largely under genetic control, psychologists have been much less successful at pinning down all the genes involved. This is because several candidate genes have been implicated and each genetic variation only increases the risk of OCD by a fraction.
The consequence is that a genetic explanation is unlikely to ever be useful because it provides little predictive value.
EVALUATION OF THE NEURAL EXPLANATION
Give one strength of the neural explanation of OCD
There is evidence to support the role of some neural mechanisms in OCD. Some anti-depressants work purely on the serotonin system, increasing levels of this neurotransmitter.
Such drugs are effective in reducing OCD symptoms and this suggests that the serotonin system is involved in OCD which is a strength of the explanation.
EVALUATION OF THE NEURAL EXPLANATION
Outline the two limitations of the neural explanation of OCD
- it doesn’t work for everyone
* cause and effect issues
