Everyone know about UV, vitamin D and blue light to help your circadian rhythm.
But very few people know that we need infrared to keep inflammation in check. Our mitochondria use infrared light to create melatonin that remove oxidative stress from normal metabolic respiration. The melatonin we know from the brain is merely the backup plan for the night.
We have create an environment completely void of infrared (IR blocking windows, living inside, led light) and we get a lot of inflammation that trigger autoimmune disease, depression, etc.
I think that one reason why it feel so good to snuggle up to a fireplace in the winter (way better than just the heat)
This research has been done on human and mice, replicated, etc. I think there is no money to be made by the pharma (in fact a lot of money to be lost) if this was widespread knowledge.
I bought a cheap infrared heat dish at costco and healed a terrible eczema i have every winter for 20 years in a few days.
I implore everyone who has an autoimmune disease or depression to try it out. For sure the sun is better, but this can help in the middle of winter.