depression
"I have attempted suicide three times in my life. The first two times were before I knew of Lithium and the third was when I took a break from Lithium, foolishly thinking I had gotten better. Lithium, at 900mg, almost completely eliminates the suicidal ideation. Symptoms of depression still present, however much better. Side effects I have had are weight gain (5 lbs?), frequent urination/thirst, thinning of my hair and sometimes I feel tired. I'll take these side effects any day over how I used to feel. This medicine has kept me alive. 

If you have recurring suicidal ideation, I would highly recommend."