The Biological Explanation of OCD Flashcards
How does the biological approach see OCD?
Being similar to physical illnesses caused by abnormal biological processes.
What are the 2 main biological explanations for OCD?
Genetic and Neural explanations
What is the genetic explanation?
Hereditary influences through genetic transmission from parent to offspring.
What is the neural explanation?
Abnormal functioning of neural mechanisms and neurotransmitters.
What are the main two genes involved in the genetic explanation?
COMT and SERT gene
Why is the gene called the COMT gene?
It is involved in the production of catechol-O-methyltransferase
What does the COMT gene do?
Regulates the production of the neurotransmitter dopamine.
Why is the COMPT gene linked to OCD?
As it regulates dopamine which is implicated to OCD.
One form/allele of the COMT gene is more common in what?
OCD patients than people without the disorder.
One form/allele of the COMT gene produces what?
Produces lower activity of the COMT gene and higher levels of dopamine
What is another name for the SERT gene?
5-HTT
What does the SERT gene do?
Affects the transport of serotonin creating lower levels of the neurotransmitter
What are low levels of serotonin associated with?
OCD
Ozaki et al. Found out what about the SERT gene?
A mutation of the gene in 2 unrelated families where 6/7 had OCD
What is the hormone involved in the neural explanation?
Serotonin
What does serotonin do?
Regulates mood
Lower levels of serotonin are associated with what?
Mood disorders
What is further support for the role of serotonin in OCD?
It comes from research examining anti-depressants
What has been found about drugs that increase serotonin levels?
They are effective in treating OCD
Higher levels of dopamine as associated with what?
Symptoms of OCD particularly the compulsive behaviour.
What are the two regions in the brain that have been implicated with OCD?
Basal ganglia and orbitofrontal cortex
What does the orbitofrontal cortex (OFC) do?
Converts sensory information into thoughts and impulses including ‘worry signals’
What have PET scans found about the orbitofrontal cortex (OFC)?
Higher activity in patients with OCD
A suggestion is that the heightened activity in the orbitofrontal cortex increases what?
The conversion of sensory information and worry signals to actions resulting in compulsions
What is the basal ganglia?
A brain structure involved in multiple processes such as the coordination movements.
What is the name of the nucleus located in the basal ganglia?
Caudate nucleus
What does the caudate nucleus do?
Suppress signals from the OFC
What is the link between the caudate nucleus and OCD?
Those with OCD have a difficulty in switching off or ignoring signals actions sent from the OFC as the caudate nucleus is damaged
What happens if the caudate nucleus is damaged?
Prevents patients from stopping compulsive behaviours.
The link between the caudate nucleus is supported by what?
PET scans of patients with OCD taken while their symptoms are active. Scans show heightened activity in the OFC.
What did Comer et al report about serotonin?
It plays a key role in the operation of the OFC and the caudate nuclei.
What did Comer et al report about abnormal levels of serotonin?
Cause the areas of the OFC and caudate nuclei to malfunction.
What does high levels of dopamine do to the basal ganglia where it is located?
Over activity
A strength of the genetic explanation is that there is evidence that people are vulnerable to OCD because of their genetic makeup. What evidence supports this?
A review of twin studies found that 68% of identical twins shared OCD compared to 31% of non-identical twins.
A strength of the genetic explanation is that there is evidence that people are vulnerable to OCD because of their genetic makeup. How can this be evaluated?
There is supporting evidence for genetic influence on OCD.
Validity of the theory increases.
Make effective treatment to alter levels of serotonin and dopamine.
A weakness of the genetic explanation is that twin studies assume that identical twins are only more similar than non-identical twins in terms of their genes. What evidence supports this?
They overlook that identical twins may also be more similar in terms of shared environment as non-identical may be boy and girl who have different experiences.
A weakness of the genetic explanation is that twin studies assume that identical twins are only more similar than non-identical twins in terms of their genes. How can this be evaluated?
Limits the validity of using evidence from twin studies.
It is not clear if findings are due to genetics or similar environment .
Impossible to determine genes as a causal factor in OCD.
A strength of the neural explanation what Max et al. found. What evidence is there to support this?
When the basal ganglia is disconnected from the frontal cortex during surgery, OCD-like symptoms are reduced.
A strength of the neural explanation what Max et al. found. How can this be evaluated?
Support for the role of the basal ganglia and OCD.
Supports the validity
Implications for possible treatment for OCD focused on activating the basal ganglia.
A weakness of the neural explanation is that environmental factors can also trigger or increase the risk of developing OCD. What evidence supports this?
It has been found that over half of OCD patients in one study had a traumatic experience in their past, and that OCD was more severe with more trauma.
A weakness of the neural explanation is that environmental factors can also trigger or increase the risk of developing OCD. How can this be evaluated?
The biological explanation is reductionist.
Environmental factors play a part and OCD may be nature and nurture.
According to diathesis-stress model biological factors may be predisposition rather than a cause.
