Biological approach to explaining OCD
Terms in this set (37)
What type of disorder is OCD?
How does anxiety arise in OCD patients?
Through obsessions (persistent thoughts) and compulsions (behaviours that are repeated over and over again)
What is the genetic explanation of OCD?
Genes are transmitted from parents to offspring - genes make up chromosomes and consist of DNA which codes physical and psychological features of an organism - includes the diathesis-stress model
What are compulsions a response to?
Obsessions - the person believes the compulsions will reduce anxiety
What are some common obsessions?
Contamination, fear of losing control, perfectionism and religion
How does the biological approach see abnormal conditions?
They are similar to physical illnesses caused by abnormal biological processes
What is another name for the biological approach?
The medical model
What are the two possible biological explanations for OCD?
Genetic and damage to neural mechanisms
What are the two genes focused on in the genetic explanation?
The COMT gene and the SERT gene
What does the COMT gene do?
Regulates the production of the neurotransmitter dopamine - which has effects on motivation and drive
What does normal amounts of the COMT gene lead to?
High levels of dopamine
Low levels of COMT
= High levels of dopamine
What does the variation of the COMT gene found commonly in OCD patients produce?
Lower activity of the COMT genes and higher levels of dopamine (greater drive to carry out compulsions)
What part of OCD is the COMT gene linked with?
What does normal amounts of the SERT gene lead to?
Low levels of seritonin
What does the SERT gene do?
It affects the transport of the serotonin, creating lower levels of this neurotransmitter
What did Ozaki's study find?
It found that a mutation of the SERT gene in two unrelated families where 6 of the 7 family members had OCD, suggesting that SERT may have some link with OCD
What are genes called if they may contribute to an illness?
What is the diathesis-stress model?
A model that suggests a person can inherit genes associated with mental health disorders which stay dormant until there is a stressor (i.e. the environment around that person)
What is a diathesis?
A vulnerability created by individual genes that can lead to a mental illness (genetic vulnerability)
What is a stressor?
It is a thing in a person's environment that affects what condition develops if any
What is the neural explanation of OCD?
The view that physical and psychological characteristics are determined by the behaviour of the nervous system, in particular the brain as well as individual neurons
abnormal levels of neurotransmitters
abnormal brain circuits
What are the abnormal levels of neurotransmitters in people with OCD?
Dopamine and serotonin
What level is dopamine thought to be at within OCD patients?
What is the conclusion about abnormal levels of dopamine based on?
Animal studies - high doses of drugs that enhance levels of dopamine induce stereotyped movements resembling the compulsive behaviours found in OCD patients
What level is serotonin thought to be at within OCD patients?
What is the conclusion about abnormal levels of serotonin based on?
On the fact that antidepressant drugs that increases serotonin activity have been shown to reduce OCD symptoms
What happens with a worry circuit?
The OFC (where minor worry originates) sends signals to the thalamus about things that are worrying, the thalamus would then send a signal back.
Normally, the caudate nucleus would intervene with this communication, suppressing the worry.
However, in someone with OCD, the caudate nucleus is damaged so it cannot stop the signals being sent between the OFC and thalamus, effectively creating a worry circuit
What does the
Surpress signals from the orbitofrontal cortex (OFC) where minor worry signals originate
What signal does the OFC send to the thalamus?
About things that are worrying e.g. potential germ hazards
When the caudate nucleus is damaged...
It fails to suppress the minor worry signals and the thalamus is alerted, which in turn sends signals back to the OFC, acting as a worry circuit
What does the thalamus normally do?
Send the worrying signal back to the caudate nucleus which would suppress the minor worry signals
Which neurotransmitter plays a key role on the operation of the OFC and the caudate nuclei?
Serotonin (abnormal levels of this might cause these areas to malfunction)
Where is the caudate nucleus located?
In the basal ganglia
What is the main neurotransmitter of the basal ganglia?
Dopamine - high levels lead to overactivity of this region (explaining why OCD sufferers have a constant overdrive)
• Nestadt et al (2000) - first-degree relative with OCD, five times greater risk of having the illness themselves
• Billett et al (1998) - meta analysis - 14 twin studies - MZ twins more than twice as likely to develop OCD if their co-twin had the disorder
• Real-world application - turn genes off, abort eggs with genes
• Studies genetic link to abnormal levels of neruotransmitters - Menzies et al (2007) - Reduced grey matter
• Two-process model contradicts genetically inherited
• Turning genes off/abort eggs with genes - playing god
• No cause and effect