I have many reasons to distrust a study like this anyway, just like a lot of medical studies trying to find causations in everyday activities. 1. If the results aren't controversial it probably wouldn't get published ("dark mode is good for your eyes" is a boring result) 2. They can discard results that contradict the thesis without having to make them public. 3. How many people do we need to trust the results of a study like this? Whatever the number you think of, they probably used less than that. When it comes to stuff like this, you can probably find studies stating the opposite anyway, it's not like there's a consensus on this stuff.