Lesson 12 - Biological Causes of OCD Flashcards
What is the biological approach to explaining OCD?
The biological approach claims that OCD is caused by genetics and neural explanations - such as neurotransmitters and abnormal brain circuits.
What are the 2 genes implicated in OCD?
The COMT gene;
The SERT gene
What is the COMT gene?
The COMT gene regulates the production of dopamine, which is associated with serotonin in OCD.
The COMT gene has been found more in OCD patients than it has in people who do not have the illness.
How is OCD classed (in a gene sense)?
OCD is polygenic. It consists of many different genes, which are known as candidate genes.
What is the SERT gene?
The Serotonin Transport gene.
This gene affects the transportation of serotonin which results in low levels of serotonin.
Where do OCD individuals have the SERT gene?
They have it on chromosome 17. A mutation in this gene causes OCD.
Who did research on the SERT gene?
Ozaki (2003). They found that 6 out of 7 family members who had OCD had a mutation of the SERT gene. The gene mutates which then causes low levels of serotonin to be produced.
This explains the link with depression.
Evaluation of genetics explanations - Nestadt
Nestadt (2000) found that people who had a first degree relative who already had OCD were 5x more likely to get OCD.
This shows that OCD is transferred genetically.
Evaluation of genetics explanations - Billett
Billett (1998) supports the idea that OCD is transmitted genetically. He did a meta analysis of 14 twin studies, and found that MZ twins were 2x more likely to both have the illness, rather than DZ twins.
This shows that OCD is genetic.
Evaluation of genetics explanations - ignores psychological and environmental factors
The concordance rate for OCD is not 100%. OCD cannot be caused entirely by genetic factors, and the genetic explanation does not take into account psychological and environmental factors that may effect the development of the illness.
Evaluation of genetics explanations - OCD is polygenic + implicated in other illnesses
OCD is polygenic, and has multiple genes implicated in it’s development. OCD has been genetically linked to other illnesses such as autism and Tourettes syndrome. This shows that OCD’s genetic cause is extremely complex. Perhaps it is not one gene that is responsible, but actually a predisposing factor.
Evaluation of genetics explanations - ignores behavioural approach
The behavioural approach would contradict the genetic explanation for OCD. The two process model would suggest that OCD can be learnt via classical conditioning, and held through operant conditioning. This view has gained large support, as OCD is often treated through behavioural therapies such as exposure.
Evaluation of genetics explanations - diathesis stress model
The diathesis stress model would argue that OCD can be caused by a combination of genes, AND an environmental trigger. Genes cannot cause OCD alone.
This means the diathesis stress model weakens the genetic argument.
Who did research into genetics and OCD?
Beekman and Cath (2005)
What was the methodology of Beekman and Cath’s research?
They did a meta analysis of twin studies on OCD that had occurred over the last 70 years.
They compared MZ and DZ twins.
They studied 10,034 twin pairs from 28 separate twin studies.
What were the findings of Beekman and Cath?
The results showed that, in children, OCD is inherited via genes, and the genetic influence ranges from 45-65%.
The results showed that, in adults, OCD is inherited via genes, and the genetic influence ranges from 27%-47%.
The conclusion was that OCD is transmitted genetically, and this was more apparent when examining children rather than adults.
Evaluation of Beekman and Cath - No controlled conditions
Most of the twin studies were not performed in controlled conditions. This means that the data is not very objective or scientific, and therefore this might affect the validity and the reliability of the results gained from this research.
Evaluation of Beekman and Cath - Gene mapping was not considered
Most of the research can be criticised because gene mapping was not taken into consideration when looking at whether OCD is genetic. Gene mapping would look closely at the DNA of the twins that had OCD, and compare this with twins that do not have OCD. There must be a comparison, to make the results more valid.
What are the two neurotransmitters implicated in the neural explanations of OCD?
Dopamine;
Serotonin;
What is dopamine?
Dopamine is a neurotransmitter that affects mood, and might be a cause of OCD.
OCD sufferers have high levels of dopamine.
What regions of the brain have been linked to dopamine activity?
The frontal lobes.
What is serotonin?
Serotonin is a neurotransmitter that affects mood. OCD sufferers tend to have low levels of serotonin, and this can cause depressive like symptoms, and also obsessive thoughts.
Where does serotonin work in the brain?
Caudate nucleus, and low levels of serotonin causes this to malfunction.
What does the claudate nucleus do?
The caudate nucleus plays a vital role in how the brain learns, alongside storing and processing memories. It works as a feedback processor, which means it uses information from past experiences to influence future actions and decisions.
Evaluation of neural explanations - Drugs
It is thought that neurotransmitters do cause OCD. Anti-depressant drugs will increase serotonin levels in OCD patients, and this does lead to a reduction of symptoms. This shows that serotonin must be implicated in causing OCD.
Evaluation of neural explanations - cause and effect issues
It cannot be certain that neurotransmitters such as dopamine and serotonin might cause OCD. The abnormal levels of them might actually be an effect of OCD. This raises causation issues.
Evaluation of neural explanations - co morbid with depression
A problem with this is that OCD is co morbid with depression. It is not clear whether low levels of serotonin cause OCD or depression or both. Therefore the link between serotonin and OCD must be investigated further.
Evaluation of neural explanations - Ciccerone
Ciccerone (2000) found that giving OCD patients low doses of the drug Risperidone helped to lower dopamine levels and alleviate some of the symptoms. Dopamine must be implicated in OCD.
Evaluation of neural explanations - Menzies
Menzies (2007) studied MRI scans, in OCD patients and their immediate family members, and compared them with controls. It was found that OCD patients and their families had reduced grey matter in key regions of the brain.
Evaluation of neural explanations - role of dopamine is not clear
High dopamine levels are also found in bipolar depression and SZ, so there is not enough research to suggest the high levels of dopamine can cause OCD. There must be other factors.
