The Biological Approach to Explaining OCD
Genetic Explanations
OCD is a good example of condition that may be largely understood as biological in nature. The
genetic explanation states that genes are involved in individual vulnerability to OCD. Lewis (1936)
observed that of his OCD patients 37% had parents with OCD and 21% had siblings with OCD. This
suggest that OCD runs in families, although genetic vulnerability is passed on, not the certainty of
OCD. According to the diathesis-stress model certain genes leave some people more likely to suffer
a mental disorder but it is not certain- some environmental stress is necessary to trigger the
condition.
Candidate genes
Candidate genes cause vulnerability for OCD. Some of these genes are involved in regulating the
development of the serotonin system. The gene 5HT1-D beta is implicated in the efficiency of
transport of serotonin across synapses.
1
, OCD is polygenic
OCD is not caused by several genes, not just one. Taylor (2013) had 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.
The COMT Gene- helps to reduce the action of
dopamine
The COMT Gene helps to reduce the action of dopamine. It is associated with the production of
dopamine which regulates the neurotransmitter dopamine. One variation of the COMT gene results
in less dopamine control which means there are higher levels of dopamine and thus variation is
more common in patients with OCD, in comparison to people without OCD.
The SERT Gene (5-HTT) affects the transport of serotonin, creating lower levels of this
neurotransmitter. Low levels of serotonin = OCD.
Different types of OCD
One group of genes may cause OCD in one person, but a different group of genes may cause the
disorder in another person. This means OCD 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.
Evaluation
There is good supporting evidence
There is evidence from a variety of sources for the idea that some people are vulnerable to OCD as a
result of their genetic make-up. Importance of genes in twin studies. Nestadt at al. reviewed
previous twin studies and found that 68% of identical twins shared OCD as opposed to 31% of non-
identical twins- this strongly suggests a genetic influence on OCD.
Too many candidate genes
Although twin studies strongly suggest that OCD is largely under genetic control, psychologists have
been less successful at pinning down all the genes involved. One reason for this is because it involves
several genes and each genetic variation only increases the risk of OCD by a fraction. A genetic
explanation is unlikely to ever be very useful because it provides little predictive value.
Environmental risk factors
It seems that environmental factors can also trigger or increase the risk of developing OCD
(diathesis-stress model). Cromer at al. (2007) found that over half the OCD patients in their sample
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
better to focus on the environmental causes as we can actually do something about.
2
Genetic Explanations
OCD is a good example of condition that may be largely understood as biological in nature. The
genetic explanation states that genes are involved in individual vulnerability to OCD. Lewis (1936)
observed that of his OCD patients 37% had parents with OCD and 21% had siblings with OCD. This
suggest that OCD runs in families, although genetic vulnerability is passed on, not the certainty of
OCD. According to the diathesis-stress model certain genes leave some people more likely to suffer
a mental disorder but it is not certain- some environmental stress is necessary to trigger the
condition.
Candidate genes
Candidate genes cause vulnerability for OCD. Some of these genes are involved in regulating the
development of the serotonin system. The gene 5HT1-D beta is implicated in the efficiency of
transport of serotonin across synapses.
1
, OCD is polygenic
OCD is not caused by several genes, not just one. Taylor (2013) had 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.
The COMT Gene- helps to reduce the action of
dopamine
The COMT Gene helps to reduce the action of dopamine. It is associated with the production of
dopamine which regulates the neurotransmitter dopamine. One variation of the COMT gene results
in less dopamine control which means there are higher levels of dopamine and thus variation is
more common in patients with OCD, in comparison to people without OCD.
The SERT Gene (5-HTT) affects the transport of serotonin, creating lower levels of this
neurotransmitter. Low levels of serotonin = OCD.
Different types of OCD
One group of genes may cause OCD in one person, but a different group of genes may cause the
disorder in another person. This means OCD 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.
Evaluation
There is good supporting evidence
There is evidence from a variety of sources for the idea that some people are vulnerable to OCD as a
result of their genetic make-up. Importance of genes in twin studies. Nestadt at al. reviewed
previous twin studies and found that 68% of identical twins shared OCD as opposed to 31% of non-
identical twins- this strongly suggests a genetic influence on OCD.
Too many candidate genes
Although twin studies strongly suggest that OCD is largely under genetic control, psychologists have
been less successful at pinning down all the genes involved. One reason for this is because it involves
several genes and each genetic variation only increases the risk of OCD by a fraction. A genetic
explanation is unlikely to ever be very useful because it provides little predictive value.
Environmental risk factors
It seems that environmental factors can also trigger or increase the risk of developing OCD
(diathesis-stress model). Cromer at al. (2007) found that over half the OCD patients in their sample
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
better to focus on the environmental causes as we can actually do something about.
2
