[Meai]

to be honest, I think this is all solely due to caffeine. I sleep 5-6h if I'm on caffeine, I sleep 8-9h if I'm off caffeine. When I first started drinking caffeinated drinks at age ~23 (yes really), I had a short period where I could still sleep full nights but eventually I was always down to 6h. In my opinion most people don't attribute any of these sleep changes to caffeine because they've been on caffeine for a long time, never fully stop and when you are younger it doesn't have this effect yet or immediately.

[medstrom]

I've had the same experience with sleeping more after my coffee runs out, but it's only temporary, lasting maximum one week.

[Emma_Goldman]

I don't think this is likely. It's well known that caffeine disrupts sleep and that you therefore need to spend more rather than less time in bed to get the same rest.

[adrianN]

I sleep 8-9h and drink however much caffeine is in about 8g of green tea leaves in the mornings.