Pain killer abuse and to a certain extent steroids abuse was also pretty frequent in the more active parts of the army.
Pain killers to get them through courses.
And steroids to get the muscle bulk up quickly.
I've been involved with medivacing a number of squaddies from Afghanistan, guys who had seriously damaged their kidneys and/or liver ODing on legal drugs and supplements attempting 'Op Massive'. Guys hammering Creatine to help build muscle mass and downing NSAIDs like Skittles in order to deal with the pain caused by over-training.
At least one that I know of had irreparable damage to both kidneys (he was medivac'd on a filter). Of course the stuff he was taking was all legal which makes it 'good' drug abuse I guess.