Biological Approach to OCD Flashcards
Nedstadt et al. 2000 (Genetic)
Found that first-degree relatives (i.e. parents, siblings or children) of OCD sufferers had a 12% chance of developing the disorder compared to a 3% risk in the general population.
What does the genetic explanation of OCD suggest?
- Genetic evidence has found that first-degree relatives of people with OCD have a greater vulnerability of developing the disorder.
- Research has also found specific type of gene that could be responsible for OCD called ‘candidate genes’. Some of these genes are involved in regulating the production of the neurotransmitter serotonin that is also implicated in OCD.
Which candidate gene is most influential in the development of OCD?
The SERT gene (or 5-HTT)
What happens if the SERT gene is impaired?
If this is impaired, it leads to diminished levels of the neurotransmitter serotonin.
In one study a mutation of this gene was found in 2 unrelated families where 6 out of 7 members had an OCD (Ozaki et al, 2003)
What is a predisposition?
A liability or tendency to suffer from a particular condition, attitude or act in a certain way
What are genetics?
Genetic properties or features of an organism
What are genes?
A unit of hereditary material which is transferred from parent to child and these determine some characteristics of offspring
What is a mutation?
Changing of the structure of a gene
What is a neurotransmitter?
A chemical substance released at the end of a nerve fibre by the arrival of a nerve impulse
What is the neural explanation for OCD?
The role of a damaged caudate nucleus and the orbitofrontal cortex
What happens if there is a damaged caudate nucleus and the orbitofrontal cortex
The caudate nucleus (located in the basal ganglia) normally suppresses signals from the orbital frontal cortex (OFC).
In turn, the OFC sends signals to the thalamus about things that are worrying, such as a potential germ hazard.
When the caudate nucleus is damaged, it fails to suppress minor ‘worry’ signals and the thalamus is alerted, which in turn sends signals back to the OFC, acting as a ‘worry circuit’.
Where is the caudate nucleus?
The basal ganglia?
How does damage of the caudate nucleus and OFC link to OCD?
If the caudate nucleus is damaged and fails to suppress these messages, minor worries become blown out of proportion and turn into obsessions that need to be acted upon in the form of compulsions.
Hence, if there is an imbalance in this area of the brain it may result in compulsive behaviour such as that seen in OCD with a heightened focus on potential future negative events (e.g. what happens if you do not carry out compulsive behaviours).
What is the role of low serotonin?
Lower levels of the neurotransmitter serotonin which influences mood regulation, anxiety, sleep and social behaviour has been linked to OCD.
The exact influence of lowered levels of serotonin is unclear, although one possibility is that serotonin plays a role in preventing behaviour repetition and therefore low levels of this neurotransmitter may be linked to the compulsions that can be displayed as a symptom of OCD.
What is the role of low dopamine?
Lower levels of the neurotransmitter dopamine have also been linked to OCD. Dopamine is released when your brain is expecting a reward. When you come to associate a certain activity with pleasure, mere anticipation may be enough to raise dopamine levels. It could be a certain food, sex, shopping, or just about anything else that you enjoy.
