The Biological approach to explaining OCD (10)

Genetic explanations (1)

Some mental health conditions are more rooted in the biological approach, OCD is understood in its biological nature.

 

One form of biological explanation is the genetic explanation. Genes are involved in individual vulnerability in OCD.

Lewis = observed that, of his 50 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 vulnerability not the certainty of OCD.

Genetic explanations (2)

Diathesis - stress model:

Notes that certain genes leave some people more likely to develop a mental or physical health condition but it is not certain.

You need the gene before you have the chemical implication, lower levels of serotonin.

Genetic explanations (3) (Candidate genes)

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 in the brain.

SERT gene - Affect transport of serotonin. Results in lower activity levels in the brain. Lowers levels of serotonin in the brain of those with OCD.

Genetic explanations (3) (OCD is polygenic)

OCD seems to be polygenic. This means that OCD is not caused by one single gene but a combination of genetic variations, that together increase vulnerability.

 

Taylor = 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 are believed to have a role in regulating mood.

Genetic explanations (3) (different types of OCD)

One group of genes may cause OCD in one person, but a different group of genes may cause the condition in another person.

 

The term used to describe this is aetiologically heterogeneous, meaning 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 a hoarding disorder

A03 - research support based on strong evidence

Some people are vulnerable to OCD because of their genetic makeup. For example the twin studies.

 

Nestadt reviewed twin studies and found that 68% of identical twins (Monozygotic) developed OCD as opposed to 31% of non-identical twins.

 

Another source of evidence for a genetic influence on OCD is family studies. Research has found that a person with a family member diagnosed with OCD is around 4x as likely to develop it as someone without it.

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

A03 - evidence for experience and nurture, argues against nature

Cromer conducted a study of 265 individuals with OCD and found that 54% of participants had suffered traumatic experiences. Cromer found and increased severity of OCD in individuals with one or more traumatic experiences.

 

We cannot disregard the influence of a person's environment, so it would be appropriate to adopt an interactionist perspective, some environmental experience is necessary to cause the condition.

The Diathesis - stress model

Neural explanations (1)

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

Neural explanations (2)

The role of serotonin

 

One explanation for OCD concerns the role of the neurotransmitter serotonin, which is believed to help regulate mood.

 

Neurotransmitters are responsible for relaying information from one neuron to another.

If a person has low levels of serotonin then usually the transmission of mood-relevant information does not take place and a person may experience low moods (another mental process may be affected).

At least some cases of OCD may be explained by a reduction in the functioning of the serotonin system in the brain.

Neural explanations (3)

Some cases of OCD, for example hoarding disorder, seem to be associated with impaired decision making. This in turn may be associated with atypical functioning of the lateral frontal lobed of the brain.

 

The frontal lobes are the front part of the brain and are responsible for logical thinking and making decisions.

There is also evidence to suggest the involvement of an area called the left parahippocampus gyrus. This area is associated with processing unpleasant emotions (disgust) and may function atypically in OCD.

A03 - supporting evidence for the neural model

Antidepressants that work purely on serotonin are effective in reducing OCD symptoms and this suggests that serotonin may be involved with OCD.

 

OCD like symptoms form part of conditions that are known to be biological in origin, such as the degenerative brain condition Parkinson’s disease, which causes muscle tremors and paralysis

If a biological condition produces OCD symptoms, then we may assume that biological processes underlie OCD, which suggests that biological factors may be responsible/underly for OCD. Showing biological reasoning for OCD.

A03 - no unique neural system (Co-morbidity, low serotonin could cause either)

The serotonin OCD may not be unique to OCD. Many people with OCD also experience clinical depression. Having two conditions together is called co-morbidity.

 

This depression probably involves 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 only OCD symptoms.

Explaining OCD is complicated by the risk that their serotonin levels may be a result of depression, another underlying factor