THEORY
Genetic Explanations of OCD:
- Mental illnesses such as OCD may have a genetic cause, similar to many physical illnesses we know of today.
STUDY
1. Family Studies:
- Helps to identify whether OCD tends to run in families, therefore showing that it is a heritable disorder.
- NESTADT et al (2000) found that first-degree relatives of an individual with OCD had an 11.7% probability of suffering from OCD, compared to only a 2.7% risk in a control group. This 5x increase in the incidence of OCD in close relatives is presumable due to shared genes.
- Similarly, if OCD is genetic, then if one twin suffers from it, the other twin would be expected to suffer from it too.
- MIGUEL et al (2005) studied identical twins and found a concordance rate of between 53 to 87%.
2. Candidate Genes:
- Specific genes that influence vulnerability to OCD.
- Influences neural activity and brain structure.
- TUKEL et al (2013) found that the COMT gene regulates activity of the neurotransmitter dopamine. One variation of the COMT gene, which results in higher levels of dopamine, is more common is people with OCD than in normal controls.
- Two other genes, SERT and 5HT1-D beta influence the regulation of serotonin and are also implicated in the development of OCD.
THEORY
Neural Explanations of OCD:
- Focuses of the role of key neurotransmitters and brain structure in causing OCD.
- If either the neurotransmitters or the brain structure have abnormalities then OCD may result.
STUDY
1. The Role of Neurotransmitters:
- The 2 key neurotransmitters that are associated with OCD are serotonin and dopamine.
- Serotonin - Low levels of serotonin are thought to be involved in creating repetitive thoughts and obsessions.
- Dopamine - High levels of dopamine can cause compulsive behaviours.
- The interplay between these neurotransmitters may therefore trigger OCD.
2. The Role of Brain Structure:
- A number of brain structures involved in OCD form a circuit have been termed as the "worry circuit". These normally function to detect a threat, make decisions about whether a response is required, and then return the system to "normal" when the threat has been coped with.
- Abnormal functioning of the "worry circuit" can cause OCD:
- The Orbitofrontal Cortex - Thought to be more active in OCD patients, indicating abnormally high "worry signals".
- The Caudate Nucleus - Not functioning normally and fails to suppress or switch off these signals.
- This reduces the ability to exert control over impulses - Impulses experienced more frequently and intensely (obsessions) and are more likely to be acted upon (compulsions).