Lithium
"I have Bipolar I mixed episodes, I've been on a number of medications in the past, but Lithium stands out as one of the worst in my case. I lived in a fog but also had some of the worst stomach issues as well. I gained quite a bit of weight too but the worst was the severe Acne I got from the drug. I never had acne like this in my life since than or before, so I know it was the medicine. It was painful, it felt like second degree burns, I went to see my doctor and all that smug @$$ said was "that's one of the side effects unfortunately".  I don't mean to sound vain but a lot of self worth comes from the outside as well as the inside and while that shouldn't be the case it's a fact for me. Be informed, not all drugs work for everyone."