Adam Engst, writing for TidBits, in reference to a 2013 paper by Piepenbrock, Mayr, Mund, and Buchner in the journal Ergonomics:
To summarize, a dark-on-light (positive polarity) display like a Mac in Light Mode provides better performance in focusing of the eye, identifying letters, transcribing letters, text comprehension, reading speed, and proofreading performance, and at least some older studies suggest that using a positive polarity display results in less visual fatigue and increased visual comfort.
I’ve never been a fan of dark mode and don’t understand its recent popularity. Whenever I give it a try, I find text harder to read, interfaces more difficult to navigate, and I feel like it’s more tiring to actually use. And I’m glad there’s some amount of evidence to support my impressions.