I've always been considered a "night owl". Since I was a child I had trouble getting to sleep until late at night and have trouble waking early in the morning. Even if I've had a lack of sleep the night before I still have trouble falling asleep at night. I've also noticed that left to my own devices my natural sleep duration is ten hours (well above normal). I am a grad student so luckily my schedule is a bit flexible and I've been taking sedatives to sleep for about 5 years now to sleep at night and lots of caffeine to stay awake in the day. Lately, I've noticed lately a new symptom. Although I always have trouble falling asleep at night (even when I'm severely sleep deprived) I tend to be able to sleep easily in the day (without any sedative) especially the late afternoon when my room is very sunny. I rarely have the chance to take afternoon naps so it's not that I'm sleeping every afternoon and this is keeping me awake at night. I think it is strange that at night i need sedative to sleep any time before 3am but I can sleep easily during the day. Does anyone know what could be causing this?