Explaining OCD

Genetic explanation

- 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 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.

- According to the diathesis-stress model certain genes leave some people more likely to develop a mental disorder. Some environmental stress is necessary to trigger the condition

What are the parts to the genetic explanation?

• Candidate genes

• OCD is polygenic

• Different type of OCD

Genetic- Candidate genes

- Researchers have identified these, which create vulnerability for OCD. Some of these are involved in regulating the development of the serotonin system. Inherited from family.

• COMT gene - more common, causing higher levels of dopamine.

• SERT gene - mutation causes lower levels of serotonin.

Genetic- OCD is 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 (2013) has analysed findings of previous studies and found evidence that up to 230 genes may be involved in OCD. Genes that have been studied include those associated with the action of dopamine as well as serotonin

Genetic- 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 heterogeneous', meaning that the origins of OCD vary from one person to another. There is also some evidence to suggest that different types of OCD may be the result of particular genetic variations, such as hoarding disorder

What are the parts to the neural explanation?

• The role of serotonin

• The decision making system

Neural- The role of serotonin

- Neurotransmitters are responsible for relaying information from one neuron to another. If a person has low levels of this neurotransmitter then normal transmission of mood-relevant information does not take place and a person may experience low moods (other mental processes may be affected).

- At least some cases of OCD may be explained by a reduction in the functioning of this neurotransmitter system in the brain

Decision-making system

- Some cases of OCD, and in particular hoarding disorder, seems to be associated with this being impaired. This in turn may 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 that are responsible for logical thinking and making decisions.

- There is also evidence to suggest that an area called the left parahippocampal gyrus is associated with processing unpleasant emotions, functions abnormally in OCD

Evaluation of the genetic explanation- Strengths

- There is evidence from a variety of sources which strongly suggests that some people are vulnerable to OCD as a result of their genetic make-up. Shown through twin studies. Gerald Nestadt (2010) reviewed twin studies and found that 68% of identical twins (MZ) shared OCD as opposed to 31% of non-identical twins (DZ). Also shown through family studies. Research has found that a person with a family member diagnosed with OCD is around four times as likely to develop it as someone without (Marini and Stebnicki 2012)

- These research studies suggest that there must be some genetic influence on the development of OCD

Evaluation of the genetic explanation- Weaknesses

- There are environmental risk factors. There is strong evidence for the idea that genetic variation can make a person more or less vulnerable to OCD. However, OCD does not appear to be entirely genetic in origin and it seems that environmental risk factors can also trigger or increase the risk of developing OCD. Cromer et al (2007) found that 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

Evaluation of the neural explanation- Strengths

- There is 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. Also, OCD symptoms form part of conditions that are known to be biological in origin, such as the degenerative brain disorder Parkinson's disease. If a biological disorder produces OCD symptoms, then we may assume the biological processes underlie OCD

- This suggests that biological factors (e.g. serotonin and the processes underlying certain disorders) may also be responsible for OCD

Evaluation of the neural explanation- Weaknesses

- The serotonin to 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