> They completely leave out that people who get sun exposure are typically doing something more active than sitting at a desk or watching TV.
Did the research (not the article) leave that out? Researchers aren't idiots and spent 10,000x as long thinking about the issue as we did about these HN posts.
>Meanwhile, that big picture just keeps getting more interesting. Vitamin D now looks like the tip of the solar iceberg. Sunlight triggers the release of a number of other important compounds in the body, not only nitric oxide but also serotonin and endorphins. It reduces the risk of prostate, breast, colorectal, and pancreatic cancers. It improves circadian rhythms. It reduces inflammation and dampens autoimmune responses. It improves virtually every mental condition you can think of. And it’s free.
The article didn't include links to the research, so who knows.
On top of that, I'd imagine that it would be hard to control for the physiological and psychological benefits of being outside (nature, activity, etc; or detriments of being indoors like air quality) unless the subjects were in a controlled environment. It would be interesting to see how the research controlled for these, if they did at all. Many studies following large cohorts in real life are not looking at proving causation, but showing correlation because they can't fully control all the variables.