Made me severely depressed and gave me suicidal thoughts.

I was becoming hypomanic/manic, and my old pdoc said that we'd nip the problem in the bud by increasing seroquel. Then well, the increase made me heavily depressed within a few days and I couldn't bear it any longer. So once we agreed to decrease the dose, the depression went away within a few days. That’s how I knew it was the Seroquel all along.