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.
