Overall, the student population at UIW is not that big on drugs. Marijuana is probably the most common drug you will come across. It is also not difficult to get a hold of the drug either, as there are quite a few students who have hookups. It really depends on who you know and who you hang around with. Keep in mind, however, that UIW is a Catholic university. Students are not likely to get caught since most of them will use this drug off campus at parties or a friend's house. Other than weed, you will not really come across other drugs.
Unlike other larger universities, UIW has a pretty clean environment when it comes to drugs and alcohol. However, you can expect that students will experiment with drugs here and there as any average college student would do. Students are more likely to get caught drinking than doing drugs though. Even though the party scene is not that big on campus, you will hear of students who keep alcohol in their dorms, often saving it for an upcoming party off campus or a small gathering with a few friends in their dorm room.