I was given six of them about eight months ago, still have two left. Next day I was in such a vile mood, paranoid and aggressive. As a result I've only taken it when in extreme distress through lack of sleep, when I know I won't be interacting with people the next day. Even so, I'm sure from my response that if I took this thing regularly I'd be in a terrible state. Doesn't make me suicidal, but so angry that I'll bang my head on the wall if people don't shut up.

I've literally only taken it when I've not slept for two or three days, to kickstart it again.

Have you tried melatonin? That really does work, and feels like natural sleep.