Biological approach to OCD

emotions dopamine is associated with

pleasure

addiction

motivation

emotions serotonin are associated with

well being

happiness

COMT gene

regulates production of dopamine

Tukel et al (2013) found that a variation of the COMT found in OCD patients produces lower activity of the COMT gene resulting in higher levers of dopamine

SERT gene

creates lower levels of serotonin

Ozaki (2003) found a mutation in the SERT gene in two unrelated families where 6/7 members had OCD

Nestadt et al (2000)

80 patients with OCD and their relatives

strong link with near family

5x great we risk of first degree relative

Billet et al (1998)

Meta analysis of 14 twin studies

MZ twins 2x more likely to develop OCD than DZ twins

diathesis-stress model

people gain a vulnerability towards OCD through genes but an environmental stressor is also required

one strength of genetic explanations is research support

Nestadt (2010) found a stronger link with OCD between near family (5x greater likelihood)

worry circuit theory

OFC sends worry signals the thalamus

Caudate nucleus monitors signals

Thalamus sends filtered version of danger back

Cormer (1998) found that serotonin plays a key role in the operation of the OFC and the caudate nuclei. abnormal serotonin levels may cause these areas to malfunction

Sukel et al (2007) found that high levels of dopamine leads to overactivity of the OFC system

in OCD the caudate nucleus is thought to be damaged so it cannot suppress signals which become increasingly excited, increasing compulsive behaviour and anxiety