Is there any proven negative health effects to energy drinks besides mixing with alcohol?

many contain ginseng, which is a no-no for anyone with high blood pressure; especially if you are taking medication for blood pressure.

also - people are very familiar with the negative problems associated with high amounts of sugar, and while many energy drinks certainly contain other things as well, much of what gives the kick as an enormous amount of sugar, in many different forms.

also - there are also many negative effects associated with caffeine, and the other major boost from many energy drinks is caffeine.

interestingly enough many energy drink companies have tried very hard to market their drinks has having something extra, or something special that sets them apart from just high sugar or high caffeine drinks.. which people are aware of, and don't often associate with energy. but much of the evidence has shown that in reality while the different additives in energy drinks may indeed have some minute effect, the majority of the so-called energy received from said drinks is just sugar and caffeine: in super high quantities.

just keep in mind that the order of ingredients listed on a product indicates the relative amounts - and look at the ingredients on energy drinks that you're considering purchasing.

There is a really interesting article in the current edition of Wired breaking down the ingredients of Red Bull. There is some weird stuff in there.
Example:
Glucuronolactone
Internet rumors claimed this was a Vietnam-era experimental drug that causes brain tumors. Luckily, that's not true. But don't crumple up your tinfoil hat yet %u2014 hardly anyone has looked into exactly what this stuff does. So little research has been done on glucuronolactone (and most of it 50 years ago) that almost all information about it is mere rumor. Users generally believe it fights fatigue and increases well-being, but that could turn out to be bull, too.

from
http://www.wired.com/science/discoveries/magazine/15-07/st_redbull

Alls i have to say about this is that i work with a guy who drinks atleast one energy drink a day(20 oz).Hes also a health nut(?).Sugar.Sugar.Sugar.I love my bottles of lipton unsweetened tea with nothing else in it, just tea.Then theres the simple lemon falvored one which contains,among other things lemon, and of course sugar, for some reason.You gotta love america.