[Psychopathology] Topic 8 - The biological approach to explaining OCD

Question 1

Genetic explanations:

Answer 1

• The COMT gene may contribute to OCD. The gene regulates dopamine production, one form of this gene is more common in OCD patients, and produces lower COMT gene activity and higher dopamine levels.
• The SERT gene may also contribute to OCD. This gene creates lower levels of serotonin, a mutation of this gene has been found in two unrelated families where 6 of the 7 members had OCD (Ozaki et al)
• High dopamine levels and low serotonin levels are associated with OCD

Question 2

Neural explanations

Answer 2

• The oribitofrontal cortex of the frontal lobes and the caudate nucleus part of the basal ganlia are thought to be abnormal in people with OCD.
• Serotonin plays a key role in the operation of these structures whilst dopamine is the basal ganglia’s main neurotransmitter. Low levels may cause the area to malfunction, Damage to the caudate nucleus fails to suppress minor worry signals from OFC, creating a worry circuit.

Question 3

The role of genetic factors is supported by family studies of OCD

Answer 3

• The role of genetic factors is supported by family studies of OCD
• For example, Nestadt et al found that people with a first degree relative with OCD are more at risk of developing the disorder (the diathesis-stress model)
• However families typically share environments as well as genes
• This means that environmental factors could also play a part in the development of OCD

Question 4

Additional support for the role of genetic factors come from twin studies

Answer 4

• Additional support for the role of genetic factors come from twin studies
• For example Billet et al found a higher concordance rate for OCD in MZ than DZ
• However the concordance rate for MZ twins is never 100%
• This means that environmental factors must also play a role in OCD