Epistemic status: n=1, strong, life changing results.

TLDR: Light glasses, in combination with turning all your lights red at night, and optionally melatonin, can treat non-24. Light glasses can also be a competitive alternative to lumenators for SAD.

My non-24 before this treatment:

Data taken from my CPAP.
Vertical lines are sleep periods; the x-axis is individual days, and the y-axis is the time in the day.
Notice how my sleep keeps wrapping around every two weeks.

And after:

What is non-24?

Non-24 is "non-24-hour sleep disorder." Healthy people's bodies tell them to go to sleep and wake up at the same time every day, i.e. every ~24 hours. For people with non-24, however, these drift around, such that if you wake up at 8 am one day, you wake up at 9am the next day, then 10 am the next, and so on until you're waking up at midnight a couple weeks later. This is akin to having a daily circadian rhythm length of 25 hours, compared to most people's ~24; hence "non-24." This is a pretty awful problem to deal with, since either half the time you are in the middle of your day when everyone else is winding down or asleep, or you are sleep deprived!

Aside: How do sleep rhythms even work?

There's (at least) three rhythms:

"Process C" (for Circadian), the driver of wakefulness: There is a little clock in your brain called the suprachiasmatic nucleus, which tracks how long your day/night cycle is and sends signals for you to be awake. It takes the majority of its cues from ipRGCs, a type of cell in your eyes that controls pupillary reflex but contributes little to color vision. Blue and green light activate them very strongly, and red light activates them almost not at all.

"Process S" (for Sleepiness), the driver of sleepiness: This sends signals for you to go to sleep, based on the buildup of various metabolites in your brain. They accumulate steadily over the day and are what causes active drowsiness (while the "sleep" signal of Process C is just the withdrawal of the wakefulness signal). Antagonism of the receptors that check for those metabolites relieves this sleep pressure; this is how caffeine works, by blocking receptors for adenosine, one of the major metabolites.

There are also ultradian cycles, or "basic rest-activity cycles." They vary between people, bu

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