I just recently read something about sleep cycles which was pretty interesting.
They were talking about those sleep stages/levels which each last 60-90 minutes, then entering the next phase/level...subsequently with each of those longer phases separated by an "almost awake" gap...here:
I also used to sleep the full 7-8 hours for the longest time, feeling awful all around if i didn't get my "full" sleep - but recently switched to a very weird sleep pattern, YES, usually about 4 hours...then i am awake, i get up, do some stuff, work or game, whatever...and then sleep another 3-4 hours in the afternoon when i am tired again.
And..it totally works! I actually enjoy that sleep in the afternoon, maybe it's also since we moved to Spain where everyone has siesta at that time anyway. (Since its so fricking hot here all the time, i start to understand why people do this..lol)
What i am saying...nothing speaks against splitting up your sleep if your daily routine allows.
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Edit: As opposed to following a "unnatural" and forced cycle, eg. imposed to you by your work/school schedule etc. which would require you to stay up "all day long"....and then sleep 8 hours "at night"...so WTF if you are actually tired, say, around noon....or "need" to sleep 8 hours but are not tied at night? I noticed when i do those 4 hour sleeps...i do actually go to bed *when* i am in fact tired, often eg. around 1 or 2pm... (i work at home so i can do this)..rather than forcing my body to some schedule. And this is likely why you need meds, because you try to sleep at the wrong times, your inner clock might just be wired differently. So, if you can, you should try those 3-4 hour sleeps instead.