Jeffrey M Schwartz in The Mind and the Brain writes of his studies on patients with Obsessive Compulsive Disorder.
He has successfully helped them by asking them to consiously inhbit the brain circuitry that creates the disorder and giving them the direction or instruction to do something else to create a new neural pathway.
He claims this as to be something very new, so I assume he has not come across FM Alexander’s work on consciously inhibiting brain circuitry of his vocal habit, best described in Chapter 1 of The Use of The Self, Evolution of a Technique. The exciting thing is that inthe last ten years this conscious direction has been scientifically proved with PEP scans to alter brain chemistry. FM didn’t have modern scientific investigations to back him up.
In an interview http://www.youtube.com/watch?v=ycnIO4o9vbE he states that he helped Leonardo diCaprio on The Aviator in portraying Howard Hughes who also suffered OCD: not only in his characterisation but also in relieving Leo from the symptoms afterwards as being a good method actor he actually gave himself OCD for 3 months after filming had stopped.
‘when actors portraya role they change how the seratonin in their brain works.’
http://www.youtube.com/watch?v=d7ucqimdau8&feature=related
Having a habit you wish to change is not the same as having OCD, but there is a correlation in the method of how to overcome it.