Psychopathology Learning Table 5: The Biological Approach to Explaining OCD
AO1
Genetic Explanations
Neural Explanations
Some mental disorders seem to have a stronger biological component than others, and OCD is a good example of this. One form of biological The genes associated with OCD are likely to affect the level of key
explanation is the genetic explanation.
neurotransmitters as well as the structures of the brain. These are neural
Genes are involved in individual vulnerability to OCD. Lewis (1963) observed that of his OCD patients 37% had parents with OCD and 21% had explanations.
siblings with OCD. This suggests OCD runs in families – or at least the vulnerability of having OCD passes on, not necessarily the disorder
itself.
The Role of Serotonin
According to the diathesis-stress model certain genes leave some people more likely to suffer a mental disorder but it is not certain – some
Serotonin is believed to help regulate mood. Neurotransmitters are
environmental stress (experience) is necessary to trigger the condition.
responsible for relaying information from one neuron to another. If a person
has low levels of serotonin then normal transmission of mood-relevant
Candidate Genes
information does not take place and mood (and sometimes other mental
Researchers have identified genes, which create vulnerability for OCD, called candidate genes. Some of these genes are involved in
processes) are affected. At least some cases of OCD may be explained by a
regulating the development of the serotonin system. For example, the gene 5HT1-D beta is implicated in the efficiency of transport of
reduction in the functioning of the serotonin system in the brain.
serotonin across synapses.
Decision-Making Systems
OCD is Polygenic
Some cases of OCD, and in particular hoarding disorder, seem to be associated
However, like many conditions, OCD seems to be polygenic. This means that OCD is not caused by one single gene but that several genes are with impaired decision making. This in turn may be associated with abnormal
involved.
functioning of the lateral (side bits) of the frontal lobes of the brain. The
Taylor (2013) has analysed findings of previous studies and found evidence that up to 230 different genes may be involved in OCD. Genes
frontal lobes are the front part of the brain (behind your forehead) that are
that have been studied in relation to OCD include those associated with the action of dopamine as well as serotonin, both neurotransmitters
responsible for logical thinking and making decisions.
believed to have a role in regulating mood.
There is also evidence to suggest that an area called the left parahippocampal
Different types of OCD
gyrus, associated with processing unpleasant emotions, functions abnormally
One group of genes may cause OCD in one person but a different group of genes may cause the disorder in another person the term used to
in OCD.
describe this is aetiologically heterogeneous, meaning that the origin (aetiology) of OCD has different causes (heterogeneous).
There is also some evidence to suggest that different types of OCD may be the result of particular genetic variations, such as hoarding
disorder and religious obsession.
AO3: Evaluation of the Biological Approach to OCD
Supportive Evidence
Reductionist
Supportive Evidence
P: One strength of genetic explanations for OCD is that there is good
supportive evidence.
E: For example, Nestasdt et al (2010) reviewed previous twin studies
and found that 68% of identical twins shared OCD as opposed to 31%
of non-identical twins.
E: This is a strength because it strongly suggests a genetic influence of
OCD. It supports the claims that some people are more vulnerable to
OCD as a result of their genetic make-up.
L: As a result, the credibility for genetic explanations of OCD is
increased, in turn increasing the explanatory power overall for the
biological approach to explaining OCD
P: One weakness of the genetic explanations for OCD is that it is
reductionist.
E: For example, it ignores the potential influence of
environmental factors that may trigger or increase the risk of
developing OCD, which is suggested by the diathesis-stress
model.
E: This is an issue because it has been found that over half the
OCD patients in a study conducted by Cromer et al (2007) had a
traumatic event in their past, and that OCD was more severe in
those with more than one trauma. This suggests that OCD
cannot be entirely genetic in origin, at least not in all cases. It
may be more productive to focus more on environmental
causes because we can do something about these.
L: Consequently, the credibility of the genetic explanations of
OCD and the biological approach to explaining OCD overall is
reduced.
P: One strength of neural explanations for OCD is that there is supportive
evidence.
E: For example, some antidepressants work work purely on the serotonin system,
increasing levels of this neurotransmitter. Such drugs are effective in reducing
OCD symptoms . Also according to Nestasdt et al (2010) OCD symptoms form part
of a number of other conditions that are biological in origin e.g. Parkinson’s
Disease.
E: This is a strength because it suggest that the serotonin system is involved in
OCD as the drugs tackle that system directly and have alleviated symptoms of
OCD, and Nestasdt’s research suggests that the biological processes that cause the
symptoms in those conditions may also be responsible for OCD.
L: As a result, the credibility for neural explanations of OCD is increased, in turn
increasing the explanatory power overall for the biological approach to explaining
OCD.