Biological approach to explaining OCD

• The COMT gene which regulates dopamine production, may contribute to OCD. A less active form of this gene is more common in OCD patients, and produces higher dopamine levels
• The SERT gene may also contribute to OCD by reducing serotonin levels. A mutation of this gene has been found in two unrelated families where six of the seven members had OCD
• Diathesis-stress: each gene only creates a vulnerability for OCD. Other factors, such as childhood experience, provide the trigger from the condition to develop
• High dopamine levels and low serotonin levels are associated with OCD
• High doses of drugs that enhances dopamine induce stereotypical movements in rats, whilst antidepressants drugs, which increase serotonin activity, reduce the symptoms of OCD
• The orbitofrontal cortex (OFC) of the frontal lobes and the caudates nucleus, part of the basal ganglia, are thought to be abnormal in people with OCD. Damage to the caudate nucleus fails to suppress minor ‘worry’ signals from the OFC, creating a worry circuit
• Serotonin plays a key role in the operation of these structures, and low serotonin levels may cause them to malfunction. Dopamine is the basal ganglia’s main neurotransmitter, so high dopamine levels lead to overactivity of this region