What time do normal adult human beings get up in the morning? I mean spontaneously, without alarm clocks or someone yelling that it's time to get up. I'd suggest 6-9 a.m. as a normal range. Most people without sleep disorders and with healthy habits are hard-coded to wake up within that range. Scandinavians call the 'larks' who wake up at 6 "A-people" and the 'owls who wake up at 9 "B-people". Scientists refer to Morningness-Eveningness.

There are three disorders which hard-code people to wake up outside of that range. Two of these are very uncommon:

ASPS (Advanced Sleep-Phase Syndrome) has been studied. It runs in families and the faulty gene has been identified. These people have to go to bed around 7 p.m.

Non-24 affects mostly people who are totally blind. They live by a 25-27 hour clock, going to bed 1-2 hours later each day. Every few weeks, they are "normal" for a couple of days.

DSPS (Delayed Sleep-Phase Syndrome) affects one or two adults in a thousand. (In addition there is an adolescent variety which goes away. Adults over 25 with DSPS aren't going to be cured any time soon.) Sufferers can lie in bed, awake, for hours until their hard-coded sleepy time arrives, which can be 4 a.m. or 6 a.m. or later. They generally can sleep 8-9 hours uninterrupted, if allowed to.

There are some differences between "B-people" as I defined it above and people with DSPS. It would appear that the B-Society lumps these people together into one group -- which can be OK if we're all aware and agreed.

More on this later if any interest is shown.

--DSPS
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