Do Klingons get depressed?
Think about it. What would a depressed Klingon be like? Would it, could it, happen to them? Klingons are all about honor and glory and being a proud warrior, we've all seen it. Would it be considered dishonorable or weak for a Klingon to get depressed or sad?
"If the world was perfect, it wouldn't be." - Yogi Berra