Biological Approach to Explaining OCD

Genetic Explanations:Genes are involved in individual vulnerability to OCD. Lewis observed that of his OCD patients, 37% had parents with OCD and 21% had siblings with OCD. This suggests that OCD runs in families although only vulnerability is passed on, not the certainty. 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:Researchers have identified genes which create vulnerability for OCD called candidate genes. Some of these genes are involved in regulating the development of the seratonin system. OCD is Polygenic:OCD is polygenic meaning that it is caused by several genes. Taylor analysed findings of previous studies and found evidence that up to 250 different genes may be involved in 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. The term used to describe this is aetiologically heterogenous meaning that the origin (aetiology) of OCD has different causes (heterogenous). There is evidence to suggest that different types of OCD may be the result of particular genetic variables such as hoarding disorder and religious obsession.

Evaluation: There is evidence that some people are vulnerable to OCD as a result of their genetic make-up. One of the best sources of evidence for the importance of genes is twin studies. Nesradt 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 suggests a genetic influence on OCD 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 appears tht several genes are involved and that each genetic variation only increases the risk of OCD by a fraction. The consequence is that a genetic explanation is unlikely to ever be very useful because it provides little predictive value Environmental factors can also trigger/influence the risk of developing OCD (the diathesis stress model) e.g. Cromer et al. 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 more productive to focus on the environmental causes because we are more able to do something about these

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 seratonin:One explanation for OCD concerns the role of the neurotransmitter seratonin, which is believed to help regulate mood. Neurotransmitters are responsible for relaying information from one neuron to another. If another person has low levels of seratonin then neural transmission of mood relevant information, does not take place and mood - and sometimes other mental processes - are affected. At least some cases of OCD may be explained by a reduction in the functioning of the seratonin system in the brain. Decision-making Systems:Some cases of OCD, in particular hoarding disorder, appear to be associated with impaired decision making. This in turn may be associated with abnormal functioning of the lateral side of the frontal lobes in 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 area called the parahippocampal gynus associated with processing unpleasant emotions, functions abnormally in OCD.

Evaluation: There is evidence to support the role of some neural functions in OCD. e.g. some antidepressants work purely on the seratonin system increasing levels of this neurotransmitter. These dugs are successful in reducing OCD symptoms suggesting the seratonin system is involved in OCD Studies of decision making have shown that these neural systems are the same systems that function abnormally in OCD. However research has also identified oter brain systems that may be involved sometimes but no system has been found that always plays a role in OCD. Therefore we cannot claim to really understand neural mechanisms involved in OCD There is evidence to suggest that various neurotransmitters and structures of the brain do not function normally in patients with OCD. However this is not the same as saying that this abnormal functioning causes OCD. These biological abnormalities could be a result of OCD rather than a cause