L12 - The Biological Approach To Explaining OCD

Question 1

What are the genetic causes of OCD?

Answer 1

• The COMT gene

- The SERT gene

Question 2

How does the COMT gene cause OCD?

Answer 2

• OCD can be inherited with genetic vulnerability or predisposition
• OCD is polygenic, and many genes are responsible for causing it
• These genes are known as candidate genes
• The COMT gene regulates the amount of dopamine released (high levels = OCD), and this causes OCD
• The COMT gene is more common in OCD patients

Question 3

How does the SERT gene cause OCD?

Answer 3

• affects the transportation of serotonin leading to low levels of serotonin.
• low levels of serotonin = low mood and depressive symptoms)
• 6/7 family members who had OCD had a mutated SERT gene

Question 4

Evaluation of genetic explanations (+)

Answer 4

• Nestadt (2000) found that people with a first degree relative (immediate family) with OCD were 5x likely to get it.
• Billett (1998) found that OCD is twice more likely to be concordant in identical monozygotic twins rather than dizygotic non-identical twins

Question 5

Evaluation of genetic explanations (-)

Answer 5

• The concordance rate for OCD is not 100%, so cannot be caused entirely by genetics, and fails to understand other factors contributing to it
• OCD is polygenic and is genetically linked to other illnesses, so it is very complex. The gene could be a predisposing factor for many illnesses
• The behavioural approach thinks OCD is learnt via classical conditioning and maintained through operant conditioning. OCD is often treated via exposure (a BT treatment)
• The diathesis stress model says OCD is caused by a combo of genes and a trigger in the environment. Both need to be combined for OCD to happen

Question 6

What neurotransmitters could explain OCD

Answer 6

• Dopamine

- Serotonin

Question 7

What does dopamine do?

Answer 7

• Linked to hyperactivity in basal ganglia, resulting in repetitive motor functions (compulsions)
• OCD patients have high dopamine levels
• In animals, giving them high levels of dopamine results in similar symptoms of OCD

Question 8

What does Serotonin do?

Answer 8

• Operates caudate nucleus in basal ganglia
• Low levels = malfunction of basal ganglia.is
• Low levels of serotonin = depressive symptoms & obsessive thoughts
• Many people with OCD also have depression

Question 9

Evaluation of neural explanations (+)

Answer 9

• Antidepressant drugs increase serotonin and reduce OCD symptoms
• Ciccerone (2000) found giving patients low levels of Risperidone lowered dopamine levels and alleviate symptoms of OCD
• Menzies (2007) studied MRI scans in OCD patients and compared them with healthy controls. OCD patients and their families gasps reduced grey matter in key regions of the brain. The abnormal brain structure could be inherited via genes

Question 10

Evaluation of neural explanations (-)

Answer 10

• cause and effect: does OCD cause low levels or serotonin and high levels of dopamine or vice versa
• not clear if serotonin causes OCD because it is comorbid with depression
• not clear if dopamine causes OCD. It causes other psychological illnesses, so a combo of factors might cause it instead