Yikes. That seems pretty extreme!
One thing I like about this hypothesis as it evolves is it ties stress to acne in a simple but non-traditional way. Most people just imagine that stress "causes" the acne. This hypothesis says stress is just a symptom of what's causing the acne, not an actual cause itself. Cortisol (aka "the stress hormone", though it's possible to take that label too literally) fluctuates in opposition to melatonin. As melatonin shuts down during the early morning, cortisol levels start to rise to help you become alert and awake. If you want to experience more hours of cortisol each day (also blamed in late-night infomercials for storing fat around your belly) just get less hours of melatonin surge each night.
Disturbed sleep is also a feature of both depression and a disrupted melatonin cycle, which led me to this relatively new study.
Effect of sunlight exposure on cognitive function among depressed and non-depressed participants.
That's what I would have hoped the result would be. We're just at the beginning of researchers starting to pay attention to the importance of the daytime portion of the melatonin cycle in affecting the nighttime portion of the cycle. Of course, it's always possible other direct retina-to-brain effects are in play besides just the suppression of daytime pineal melatonin.
The ability of the sunlight to help us avoid carbohydrate malabsorption that can screw up digestion of tryptophan (the fuel required for making melatonin) seems really likely to be part of how sunlight (indirectly) affects the brain. It is possible for melatonin to be synthesized from tryptophan outside the brain, but it seems like the really big system-wide dose of melatonin still comes from the nightly pineal gland production. That makes me think that getting the tryptophan across the blood-brain barrier is still potentially important to results (including depression and acne).
Now that I know more about getting the tryptophan absorbed by the gut, I need to go back to some experiments with moving more tryptophan in to the brain. Exercise helps move it, and carbs in the absence of fat (taking a glucose pill on an empty stomach) can do it as well. Timing probably matters (want to get the tryptophan in place near the time the pineal gland starts to want to burn it up, I imagine). I will redo my old experiment of early supper, and then taking a glucose pill before doing an aerobic run on an empty stomach within 1-2 hours of bedtime.