9. biological approach to explaining OCD

Question 1

GENETIC EXPLANATIONS

Genes are involved in individual vulnerability to OCD.
Lewis observed that of his OCD patients,

Answer 1

37% had parents with OCD and 21% had siblings with OCD. This suggests that OCD runs in families, although what is probably passed on from one generation to the next is genetic vulnerability not the certainty of OCD.

Question 2

GENETIC EXPLANATIONS

According to the diathesis-stress model

Answer 2

certain genes leave some people more likely to develop a mental disorder but it is not certain. Some environmental stress is necessary to trigger the condition.

Question 2

GENETIC EXPLANATIONS

CANDIDATE GENES
Researchers have identified genes, which create vulnerability for OCD, called candidate genes. Some of these genes are involved in regulating the development of the serotonin system. For example, the gene

Answer 2

5HT1-D beta is implicated in the transport of serotonin across synapses - it increases the number of reuptake proteins in the post synaptic membrane, so serotonin is taken up faster before it can bind to the receptors.

Question 3

GENETIC EXPLANATIONS

OCD IS POLYGENIC
However, like many conditions, OCD seems to be polygenic. This means that OCD is not caused by one single gene but by a combination of genetic variations that together significantly increase vulnerability.
Taylor

Answer 3

analysed findings of previous studies and found evidence that up to 230 different genes may be involved in OCD.
Genes that have been studied in relation to OCD include those associated with the action of dopamine as well as serotonin, both neurotransmitters believed to have a role in regulating mood.

Question 3

GENETIC EXPLANATIONS

AO3: limitation of BIOLOGICAL APPROACH TO EXPLAINING OCD

environmental risk factors - Cromer

Answer 3

There are environmental risk factors that also affect the development of OCD.
There is strong evidence for the idea that genetic variation can make a person more or less vulnerable to OCD, however it does not appear to be entirely genetic in origin and environmental risk factors also trigger or increase the risk of developing OCD. Cromer et al. found over half the OCD clients in their sample had experienced a traumatic event in their past - OCD was also more severe in those with one or more traumas.
This means that genetic vulnerability only provides a partial explanation for OCD.

Question 4

GENETIC EXPLANATIONS

AO3: strength of BIOLOGICAL APPROACH TO EXPLAINING OCD

research support - Nestadt, Marini

Answer 4

There is evidence from a variety of sources which strongly suggest that some people are vulnerable to OCD as a result of their genetic makeup.
Nestadt et al. reviewed twin studies and found 68% of identical twins as opposed to 31% of non-identical twins. Furthermore, family studies by Marini has shown a person with a family member diagnosed with OCD is around 4 times as likely to develop the disorder as someone without.
These research suggest that there must be some genetic influence in the development of OCD.

Question 5

NEURAL EXPLANATIONS

The genes associated with OCD are likely to affect the levels of key neurotransmitters as well as structures of the brain - these are neural explanations.

THE ROLE OF SEROTONIN: One explanation for OCD concerns the role of the neurotransmitter serotonin, which is believed to help regulate mood.

If a person has low levels of serotonin..

Answer 5

Neurotransmitters are responsible for relaying information from one neuron to another. If a person has low levels of serotonin, then normal transmission of mood-relevant information does not take place and a person may experience low moods.
At least some cases of OCD may be explained by a reduction in the functioning of the serotonin system in the brain.

Question 6

NEURAL EXPLANATIONS

DECISION-MAKING SYSTEMS
Some cases of OCD, and in particular hoarding disorder, seem to be associated with impaired decision-making.
This in turn may be associated with

Answer 6

abnormal functioning of the lateral of the frontal lobes of the brain.
The frontal lobes are responsible for logical thinking and making decisions.

Question 7

NEURAL EXPLANATIONS

There is also evidence to suggest that an area called the left parahippocampal gyrus, associated with

Answer 7

processing unpleasant emotions, functions abnormally in OCD.

Question 8

NEURAL EXPLANATIONS

AO3: strength of BIOLOGICAL APPROACH TO EXPLAINING OCD

supporting evidence for neural model

Answer 8

One strength of the neural model of OCD is the existence of some supporting evidence.
Antidepressants that work purely on serotonin are effective in reducing OCD symptoms and this suggests that serotonin may be involved in OCD. If a biological disorder produces OCD symptoms, then we may assume the biological processes underlie OCD.
This suggests that biological factors may also be responsible for OCD.

Question 9

NEURAL EXPLANATIONS

AO3: limitation of BIOLOGICAL APPROACH TO EXPLAINING OCD

neural model - ocd-seratonin link not unique

Answer 9

One limitation of the neural model is that the serotonin-OCD link may not be unique to OCD.
Many people with OCD also experience clinical depression. Having two disorders together is called co-morbidity. This depression probably involves (though is not necessarily caused by) disruption to the action of serotonin. This leaves us with a logical problem when it comes to serotonin as a possible basis for OCD. It could simply be that serotonin activity is disrupted in many people with OCD because they are depressed as well.
This means that serotonin may not be relevant to OCD symptoms.