The Biological Approach to Explaining OCD

Question 1

What are two genes identified which may contribute to OCD

Answer 1

The COMT gene and the SERT gene (5-HTT)

Question 2

Explain how the COMT gene may contribute to OCD

Answer 2

COMT regulates the production of dopamine, and one allele has been found to be more common in those with OCD than the general population. This variation produces lower activity of the COMT gene and higher levels of dopamine.

Question 3

Explain how the SERT (5-HTT) gene may contribute to OCD

Answer 3

SERT (5-HTT) affects the transportation of serotonin, creating lower levels of serotonin. These lower levels of serotonin are also implicated in OCD, and a study by Ozaki et al found a mutation of the gene in two unrelated families where 6 of the 7 family members had OCD.

Question 4

Why is it unlikely there is a simple link between singular genes, like the SERT and COMT gene, and a complex disorder like OCD

Answer 4

Genes like SERT are also implicated in other disorders like depression and PTSD, which suggests that each individual gene only creates a vulnerability for OCD as well as other conditions like depression, and that other stressors affect what condition develops or even if a mental illness develops. This is why people may have a COMT or SERT gene and suffer no effects

Question 5

What levels of neurotransimitters effect OCD

Answer 5

High Dopamine
Low Serotonin

Question 6

How is high dopamine associated with OCD

Answer 6

Szechtman et al found that enhanced levels of dopamine induced stereotyped movements resembling compulsive behaviours of OCD in rats.

Question 7

How is low serotonin associated with OCD

Answer 7

Pigott et al found that antidepressant drugs which increase serotonin activity have been shown to reduce OCD symptoms. In contrast antidepressants which have less effect on serotonin do not reduce OCD symtopms according to Jenicke

Question 8

Explain the worry circuit

Answer 8

The Orbitofrontal cortex sends signals to the thalamus about things which are worrying, like a potetial hazard, and from the thalamus signals are sent around the body. The Caudate Nucleus normally supresses signals from the OFC, but if it is damaged than it fails to suppress minor ‘worry’ signals and the thalamus is alerted

Question 9

How have PET scans supported the caudate nucleus

Answer 9

PET scans of patients with OCD, taken while symptoms are active, have shown increased activity in the Orbitofrontal cortex

Question 10

How are dopamine and serotonin linked to the worry circuit

Answer 10

Comer reports that serotonin plays a key role in the operation of the Orbitofrontal cortex and caudate nuclei, and so low levels of serotonin could cause these areas to malfunction
Dopamine is the main nerotransmitter in the basal ganglia, and high levels of dopamine lead to overactivity in this region

Question 11

Who found that low serotonin may cause malfunction in the worry circuit

Answer 11

Comer

Question 12

Who found that antidepressants help with OCD

Answer 12

Pigott

Question 13

Who found that rats with too much dopamine went a little OCD on us

Answer 13

Szechtman

Question 14

Who found the SERT gene in plenty of two seperate families with 6/7 members of family having OCD

Answer 14

Ozaki

Question 15

How have first-degree relative studies supported a genetic basis for OCD

Answer 15

Nestadt et al identified 80 patients with OCD and 343 of their first degree relatives, comparing them to 73 control patients without mental illness and 300 of their relatives. They found people with a first-degree relative with OCD had a 5x greater risk of having the illness themselves versus the general population.

Question 16

How have twin studies supported a genetic basis for OCD

Answer 16

Billett et al conducted a meta-analysis of 14 twin studies of OCD, and found that on average, monozygotic twins were more than twice as likely to develop OCD if their co-twin had the disorder than was the case for dizygotic twins. However concordance rates are never 100% meaning other factors must also be present

Question 17

Who conducted a meta analysis of 14 twin studies into OCD

Answer 17

Billett et al

Question 18

Who conducted first-degree relative studies into those with OCD

Answer 18

Nestadt et al

Question 19

How have studies into different disorders supported the biological basis of OCD

Answer 19

Pauls and Leckman studied patients with Tourette’s syndrome and their families, and concluded that OCD was just one expression of the same gene which causes Tourette’s syndrome. Obsessive behavior in OCD is also present in autistic children and those with anorexia. All these comorbid symptoms suggest there is no specific OCD gene, but genes act as a predisposing factor for obsessive behaviour

Question 20

Who studied people with tourettes syndrome and concluded that OCD was an expression of the same gene as tourettes

Answer 20

Pauls and Leckman

Question 21

What real life applications does the biologial approach to OCD have

Answer 21

Mapping of the human genome has led to hope that specific genes can be linked to certain disorders. For example, where one parent has the COMT gene a baby from this parent can be screened and parents can have the choice to abort the child if they have the gene. Alternatively gene therapy may be able to turn genes ‘off’ so that the disorder is never expressed.

Question 22

What issues do real life applications of the biological approach to OCD raise

Answer 22

There are many ethical issues with aborting OCD children, and the gene screeing relies on a simple relationship betweem genes and the disorder, which we have already evaluated there is not

Question 23

What is an alternative explination to OCD (other than the biological approach)

Answer 23

The two-process model can be applied to OCD, similar to the behaviourist approach to phobias. Initial learning occurs resulting in anxiety and the association is maintained as the anxiety provoking stimulus is avoided. The obsession is formed as people learn that compulsive behaviours seem to alleviate anxiety.

Question 24

What supports the two-process model of OCD

Answer 24

The successful treatment of patients using exposure and response prevention (ERP), which is similar to systematic desensitisation. Patients are exposed to the fear stimulus and at the same time prevented from performing compulsive behaviours. Albucher reprted between 60% and 90% of adults with OCD had improved considerably using ERP.

Question 25

Who reported successful results from Exposure and Response Prevention therapy

Answer 25

Albucher reported 60% - 90% of adults with OCD improved considerably