• COMT regulates the production of the neurotransmitter dopamine which has been implicated in OCD
• One form of the COMT gene has been found to be more common in OCD patients
• This variation produces lower activity of the COMT gene and higher levels of dopamine
Genetic explanation
SERT Gene
• Also known as 5-HTT
• Affects the transport of serotonin, creating lower levels of this neurotransmitter
• A mutation of this gene has been found in two unrelated families where six of the seven members had OCD (Ozaki et al)
Neural explanation for OCD
Abnormal levels of neurotransmitters
High dopamine levels and OCD
High doses of drugs that enhance levels of dopamine induced stereotyped movements resembling the compulsive behaviours found in OCD
Lower levels of serotonin associated with OCD
Antidepressant drugs that increase serotonin activity have been shown to reduce OCD symptoms, whereas antidepressants that have less effect on serotonin do not reduce OCD symptoms
Serotonin also plays role in operation of OFC and CN (Comer)
Abnormal brain circuits in OCD
Several areas in the frontal lobes of the brain are thought to be abnormal in people with OCD
The orbitofrontal cortex (OFC) sends worry signals to thalamus – if caudate nucleus is damaged these signals not suppressed – thalamus is alerted & sends signals back to OFC (worry circuit)
PET scans show a heightened activity in the OFC for OCD patients when their symptoms are active
