I'm a junior academic, recently a postdoc, and I saw a little bit of ADHD stimulant use among peers, and the increasing popularity of modafanil. Basically just due to publication pressure; in my field assistant professors at a top flight university have to write not one but two peer reviewed books to get tenure. Others go in an orthogonal direction and get obsessed with intense exercise routines, also with the aim of increasing those ~six hours of usable cognitive time per day.

MDMA and cannabis are both quite popular and talked about openly but I think that's more a general reflection of the culture in places like NYC and the Bay Area, where I have personal experience.

Good luck with the book by the way. One word of warning: please try very hard to avoid falling into a simplistic narrative that will contribute to drug prohibition. Criminalization of drugs has, IMO, ruined far more lives than drugs themselves. A former Columbia colleague, Carl Hart, professor in the psych department, has written a lot on this and might be worthwhile as an interview subject for your book. Personally I think he sometimes pushes too far in the opposite direction, but he is nevertheless an important public voice speaking up against decades of scaremongering.