6-12 month minimum, once you are on the right dose with the proper response. It has more to do with complex biochemistry mixed with behavioral change. These meds are not harmful, and if you come off the meds and relapse you will need to be on it or another med for a minimum of 2 years, and from there if it fails for life. It is best to stay on the med as long as your doc says, if you have side-effects mention them to your doc as most of them are treatable.

Dr.S.