OCD (obsessive compulsive disorder) is characterized by obsessions (uncontrollable thoughts) and compulsions (repetitive behaviors).  It is believed that OCD may have biological causes which can be helped with medications such as selective serotonin reuptake inhibitors.  SSRIs help regulate levels of serotonin in the brain.   Even with medication, it is well recognized that talk therapy can be effective with the treatment of OCD. 

Talk therapy for OCD can help you recognize uncontrollable thoughts and teach alternative responses for those thoughts.  Additionally, these uncontrollable thoughts can lead to anxiety.   The feelings of anxiety are often what lead to the repetitive behaviors as it is felt that if the compulsions are completed, the anxiety will be relieved.  Talk therapy can help you recognize these patterns of anxiety and ways to cope with and relieve it while reducing or eliminating compulsive behaviors.