What does it mean when someone looks like they're in a trance?

What does it mean when someone is talking to you and they don't break eye contact throughout the whole conversation, while staring into your eyes with a blank stare (are they hiding something?). This is also accompanied by the person speaking very slowly, and taking a long time to answer/process a simple question, almost like they're hypnotized. I know for a fact drugs is not the problem.