Three. Anything used to get to sleep

Alcohol is the clearest example and the pattern generalises. It gets you off quickly, and then it fragments the second half of the night badly, which is why people who use it to sleep are so reliably awake at four.

The same shape shows up with anything taken to knock yourself out. It works for a fortnight, the fortnight ends, and the dose creeps.

If you are on a sleeping medicine your doctor prescribed, nothing here is telling you to change it. Some of them are genuinely dangerous to stop suddenly. That conversation is with the person who prescribed it, and it is a reasonable conversation to ask for.