The biological approach to explaining OCD

genetic explanation of OCD summary

the perception of OCD as transmitted through inherited factors

research support

Grootheest, Cath, Beekman & Boomsma

Twin studies on OCD: A review

genetic explanation of OCD

• OCD is polygenic (multiple genes)

• 230 candidate genes indicated

• SERT

• COMT

Serotonin

a neurotransmitter indicated in regulation of mood and anxiety

How should SERT gene function

• SERT gene produces transporter protein

• healthy amount of serotonin reuptook

SERT gene: OCD

• mutation in the SERT gene

• too much transporter protein produced

• too much serotonin reuptook

• less serotonin in body therefore anxiety, obsessive thoughts, compulsions

dopamine

a neurotransmitter in the prefrontal cortex indicated in regulation of attention, motivation and movement

how the COMT gene should function

• produces COMT enzyme

• enzyme breaks down dopamine

• healthy levels of dopamine

COMT gene: OCD

• COMT gene produces less COMT enzyme

• leading to less breakdown of dopamine

• high levels of dopamine therefore increased alertness, compulsion, obsessions

aetiologically heterogenous

different causes

combinations of genes may lead to different forms of OCD

neural explanation of OCD

the perception OCD as resulting from abnormally functioning brain mechanisms

orbito-frontal cortex

malfunctioning serotonin production- low

basal ganglia

selects actions to inhibit/ initiate

caudate nucleus- filtering ‘worry input’ and regulating behaviour. not working properly = compulsions

Describe the neural explanation of OCD (4)

Multiple functions of the brain are indicated in OCD. Two neurotransmitters are indicated in OCD. Serotonin is produced in the orbito-frontal cortex. If the orbito-frontal cortex is malfunctioning, This can lead to low levels of serotonin which are indicated in obsessions and compulsions. Dopamine in high levels is also indicated in obsessions and compulsions. Another neural explanation is the involvement of the basal ganglia (worry circuit). The malfunctioning of the caudate nucleus (meant to filter worries) can lead to obsessions and compulsions.