It is classified as a stimulant but is not an amphetamine so it doesn't produce jittery type feelings though some people sometimes have trouble falling asleep. You can fix that by taking it early in the morning and not using higher doses. Though not technically addictive like amphetamines, it does produce tolerance so sometimes needs to be increased. But in my case in took years to raise the dose. I was on it before a total of 6 years and did not experience any side effects. I have PTSD so am prone to anxiety, but I didn't experience any with Provigil. I suppose as with any anti-depressant/activating type medication it can trigger mania, but I haven't heard of that happening. It's just a warning in the literature. Provigil was given to military pilots who were sleep deprived so fatigued in order that they could be awake, calm, and focused. That is the feeling I get from it, plus a slight euphoria.