How to Warn for Something -- Help?

Dear HP People,

Okay, I am a shit researcher, and after unsuccessfully going in search of this answer, I thought, well heck, I'll just ask.  I will warn that this question may be triggery for some.

I've written a story that includes (well, the entire thing is) rape under the Imperius curse.  Is there a correct or agreed upon way to warn for that?  Any suggestions, facts, or universal truths would be very welcome!

Thank you in advance!!!