neural

• There is evidence to support the role of some neural mechanisms in OCD. For example, antidepressants that only alter levels of serotonin have been effective in reducing OCD symptoms.

  This suggests that the serotonin system is involved in OCD.

  However, many people with OCD are also depressed. This co-morbidity may mean that the depression may involve disruption to the serotonin system and this may be the true cause of the OCD.
• Research has identified that other brain systems beyond the decision-making systems may sometimes be involved in OCD.

  This explanation may not provide a comprehensive understanding of all cases of OCD and the role of decision-making systems only accounts for some individual's OCD symptoms.
• There is evidence to suggest that various neurotransmitters and brain systems do not function normally in patients with OCD. However, this doesn't necessarily mean that this abnormal functioning caused the OCD.

  The biological abnormalities may be the result of OCD rather than the cause. This is correlational evidence which does not mean the same as causation.