I am not too sure about depression pills. Are you taking these pills to help with your ibs? If you are concerned about gaining too much weight while taking these pills then you should tell your doctor and maybe he/she can put you on something else. I never heard of these types of depression pills before so I am not sure on the answer. But I'm sure it is possible as any kind of pills have side effects and weight gain and weight loss are considered to be side effects.