What's the difference between difficulty settings?

Question

Deus Ex's difficulty settings:

Considering the game's pedigree, I assume that higher settings do something in addition to boosting damage levels.

Answer 1

From the game's manual, third page (manual.pdf, included in the GOG version):

Combat Difficulty Level
When you start a new game of Deus Ex, the first thing you have to do is select the Combat Difficulty Level for your new game. There are four settings — Easy, Medium, Hard and Realistic. At higher difficulty levels you will take significantly more damage in combat. There are no other differences between difficulty levels. Once you select a difficulty level, you cannot change it without starting a new game.

Answer 2

Easy, Medium and Hard have two components - damage dealt to you and damage dealt to opponents. Easy makes you harder to kill, while Hard makes the enemy harder to kill and you easier. Realistic is different in that it makes you very easy to kill, but without making the AI harder. So you die in a headshot, from a single rocket etc. but so will the enemy.