Explaining OCD Flashcards
What is the genetic explanation?
The COMT gene
The SERT gene
Diathesis stress
What does the COMT gene do?
The COMT gene, which regulates dopamine production, may contribute to OCD.
A less active form of this gene is more common in OCD patients, and produces higher dopamine levels.
What does the SERT gene do?
The SERT gene may also contribute to OCD by reducing serotonin levels.
A mutation of this gene has been found in two unrelated families where six of the seven members had OCD (Ozaki, 2003).
What does diathesis stress do?
Diathesis stress - each gene only creates a vulnerability (a diathesis) for OCD.
Other factors, such as childhood experience, provide the trigger (stress) for the condition to develop.
What is the neural explanation?
High dopamine levels and low serotonin levels are associated with OCD.
High doses of drugs that enhance dopamine induce stereotypical movements in rats, whilst antidepressants drugs, which increase serotonin activity, reduce the symptoms of OCD.
What does the orbitofrontal cortex (OFC) do?
OFC of the frontal lobes and the caudate nucleus, part of the basal ganglia, are thought to be abnormal in people with OCD.
Damage to the caudate nucleus fails to suppress minor ‘worry’ signals from the OFC, creating a worry circuit.
What are the evaluative points?
Family and twin studies
Research support for genes and the role of OFC
Other disorders with genetic links to OCD
What is meant by family and twin studies?
Nestadt (2000) found that people with a first-degree relative with OCD had a five-times greater lifetime risk of OCD themselves, compared to risk levels in the general population.
A meta-analysis found that identical (MZ) twins were more than twice as likely to develop OCD if their twin had the disorder than non-identical (DZ) twins (Billett, 1998).
This evidence supports a genetic basis for OCD, but the concordance rates are never 100% so environmental factors must also play a role.
What is meant by research support for genes and the role of the OFC?
Menzies (2007) used MRI to produce images of brain activity in OCD patients and their immediate family members without OCD.
OCD patients and their close relatives has reduced grey matter in key regions of the brain, including the OFC.
This supports the view that inherited anatomical differences may lead to OCD in certain individuals. In the future, brain scans may be used to detect OCD risk.
What is meant by others disorders with genetic links to OCD?
Research suggests that OCD may be an expression of genes linked to other disorders such as Tourette’s and autism and so would be a characteristic of a number of different disorders.
Pauls and Leckman (1986) studied patients with Tourette’s syndrome and concluded that OCD is one form of expression of the same gene that determines Tourette’s. Obsessional and compulsive behaviour is also found in children with autism, and people with anorexia nervosa.
This supports the view that there are, not specific genes unique to OCD, but they merely act as a predisposing factor towards obsessive-type behaviour.
