Good heavens - so many frightening answers! They forgot to mention you could be hit by a bus or struck by lightening too. I have occasionally used it for a couple of years and the only side effect is improved memory. I use it occasionally to get going in a slump in long bike rides or weight-lifting. I read about 6 months ago that it seemed that the boost it gives the muscles also boosts the brain in the same way. I believe this is correct. Just use it moderately and forget about all the scarey stuff.