AO1

• The COMT gene is associated with the regulation of the neurotransmitter dopamine. One variation of the COMT gene results in higher levels of dopamine and this variation is more common in patients with OCD, in comparison to people without OCD
• The SERT gene (also known as the 5-HTT gene) is linked to the neurotransmitter serotonin and affects the transport of the serotonin (hence Serotonin Transporter), causing lower levels of serotonin which is also associated with OCD (and depression).
• Neural explanations of OCD-  Neural explanations of OCD focus on neurotransmitters as well as brain structures in the development of OCD.
• Neurotransmitters- The neurotransmitter serotonin is believed to play a role in OCD. Serotonin regulates mood and lower levels of serotonin are associated with mood disorders, such as depression. It may be that serotonin prevents the repetition of tasks, and that if it is in too low a level, or is removed too quickly from the synaptic systems, before it is able to inhibit the repetition of an action, and this may result in obsessive thoughts.  Furthermore, some cases of OCD are also associated with the reduced levels of serotonin, which may be caused by the SERT gene
• Brain structures- Two brain regions have been implicated in OCD, including the basal ganglia and orbitofrontal cortex.
• The basal ganglia is a brain structure involved in multiple processes, including the coordination of movement. Patients who suffer head injuries in this region often develop OCD-like symptoms, following their recovery. Furthermore, Max et al. (1994) found that when the basal ganglia is disconnected from the frontal cortex during surgery, OCD-like symptoms are reduced, providing further support for the role of the basal ganglia in OCD.
• Another brain region associated with OCD is the orbitofrontal cortex, a region which converts sensory information into thoughts and actions. It predicts future events and controls impulses from the limbic system. PET scans have found higher activity in the orbitofrontal cortex in patients with OCD. One suggestion is that the heightened activity in the orbitofrontal cortex increases the conversion of sensory information to actions (behaviours) which results in compulsions. The increased activity also prevents patients from stopping their behaviours.
• There is also abnormal activity in the parahippocampal gyrus, which regulates unpleasant emotions.