-Lack- of magnesium can cause cramps.
Supplementing magnesium can help lots of people since it is lacking in many people’s diets. It can also help you get more and better sleep, just avoid magnesium oxide, that will just make you poop and is unfortunately the form used in many supplements and multi vitamins.
As a child of the 80s and former smoker, I actually find the lingering smell of cigarettes in a smoking room super comforting, to the point that if a hotel has a smoking room option I take it.