Why must I try different medications for mood disorders?

Mood. Medications are switched if incomplete, inadequate response at maximum therapeutic dose, or if u cannot tolerate the medication due to side effects, or rarely, if medication is pulled off the market due to reported toxic effect.
You are not alone. Everyone responds to different meds differently. If you look at the latesy studies, it is common to not respond to several different trials. It isn't necessarily you, as we still don't clearly understand what causes mood disorders and how to treat them. If you are having trouble, i would suggest talking with your doctor. However bipolar, sub use and personality issues need special treatment.