OCD (explanation)

Question 1

What is the COMT gene’s main function?

Answer 1

It regulates the production of the neurotransmitter dopamine that has been implicated in OCD
(Dopamine affects motivation and ‘drive’)

Question 2

How is the COMT gene linked to OCD?

Answer 2

One form of the COMT gene has been found to be more common in OCD patients than people without the disorder - this variation produces higher levels of dopamine

(Tukel et al 2013)

Question 3

What is the SERT gene’s main function?

Answer 3

Affects the transport of serotonin, creating lower levels of the neurotransmitter

Question 4

How is the SERT gene linked to OCD?

Answer 4

The lower levels of serotonin are implicated in OCD

Question 5

Diathesis-stress paragraph

Answer 5

The idea of a simple link between one gene and a complex disorder like OCD is unlikely. The Diathesis-stress model argues that psychological disorders arise from the interaction of an underlying vulnerability and external stressors. Genes such as the SERT gene are implicated in many other disorders, like depression. This suggests that each individual gene only creates a vulnerability for OCD. Some could possess the COMT or SERT gene variations but suffer no ill effects. The great strength of this model is that it can be applicable to many different things.

Question 5

Neural explanations: outline the role of abnormal levels of neurotransmitters in people with OCD

Answer 5

Animal studies show that high dopamine levels are associated with symptoms of OCD, particularly the compulsive behaviours because this is a neurotransmitter for motivation and drive. Serotonin regulates mood and some cases of OCD are associated with the reduced levels of serotonin, which may be caused by the SERT gene.

Question 6

Neural explanations: outline the role of abnormal brain circuits in people with OCD

Answer 6

The caudate nucleus normally suppresses signals from the orbitofrontal cortex (OFC)

Question 7

Evaluation?

Answer 7

• Nestadt et al 2000: 80 patients with OCD and 343 of their first-degree relatives, compared them with 73 control patients without mental illness + 300 of their relatives
• people with a first degree relative with OCD had a five times greater risk of having the illness themselves
• Billett et al 1998: meta analysis of 14 twin studies of OCD: MZ twins were more than twice as likely to develop OCD if their co-twin had the disorder than was the case for DZ twins
• evidence points to clear genetic basis for OCD
  (However, the concordance rates are never 100% so environmental factors play a role too)

Question 8

Evaluation?

Answer 8

• Menzies et al 2007: used MRI to produce images of brain activity in OCD patients and their immediate family members without OCD and a group of unrelated healthy people
• OCD patients and their close relatives had reduce grey matter in key regions of the brain
• supports the view that anatomical differences are inherited and these may lead to OCD in certain individuals

Question 9

Evaluation?

Answer 9

• however there are alternative explanations
• two process model can be applied to OCD
  -> initial learning occurs when a neural stimulus is associated with anxiety
  -> the association is maintained because the anxiety-provoking stimulus is avoided
  -> an obsession is formed and then a link is learned with compulsive behaviours that appear to reduce the anxiety
• supported by the success of a treatment of OCD called exposure and response prevention (like systematic desensitisation)
• suggests that OCD may have psychological causes as well as/instead of biological