Do you have to believe, for acupuncture to work?

Well, a story - The woman who asked that question came with a bad shoulder, very painful which had last recurred some years ago, at which time, after a little treatment she recovered quickly.  Since then she has developed High Blood Pressure, has had a Stroke which she recovered well from and had developed another challenging problem.  

At first treatment didn't seem to be helping the shoulder, however, her sleep had improved.  The next session she told me  the other difficulty had had a sudden improvement then returned to a much less troublesome level.