Leaving the lights on at a dim level 24/7 - low enough to interfere with close vision, but bright enough to interfere with sleep - seems to me might be an effective way to induce real discomfort and fatigue on a prisoner and I don’t see how it could be termed torture under even the most expansive definition.
The RAP music that they play at my gym is pure torture.
You have to induce a certain level of discomfort and/or fatigue - not physical pain and not exhaustion - to break the prisoners. Only after you break them can you get then to talk. And if you are not inflicing pain or causing the mind go into a hallucinatory state, the information you get will like be accurate. No one will willingly tell you what you want to know unless it is in his best interests. Keeping them in four-star hotel conditions makes it in their best interests not to talk because they’re living it up better than they ever had it back home.