I think the problem doesn't lie as much in the use of the drug, but in the environment that leads to consumption. If we assume strong social stigma against it,

I think the problem doesn't lie as much in the use of the drug, but in the environment that leads to consumption. If we assume strong social stigma against it, and yet a majority of students end up doing it, it means there is a very strong pressure to increase performance by whatever means necessary - that is to say, that students are not in a state where they consider their workload bearable. That's in a pool of people that have been somewhat preselected for being high achievers and willing to work a lot. While medicine is a field where there should be high expectations for students (given what's at stake), I don't think keeping students and workers around the very edge of what they can mentally handle is at all healthy or worth it in the long term. We don't want burnout, we don't want to have them suffer from stress-related issues, we don't want to increase their chances of making mistakes at work, and from an ethical viewpoint we don't want them going through a miserable life even if it's a net win for society (at least I don't).