Is anything known about health risks? I could imagine that if the eye no longer has to focus on distance, that this could lead to refractive errors more quickly with excessive use. Or did I miss here something?
Since these studies, it has become harder to experiment on small kids as it would be unethical, but on the other hand there's no specific report on kids older than 13 if I remember well.
Then a decent number of adults have been using the headsets for prolonged periods without anything critical reported at this point. It should still be used with awareness of potential risks, but I don't think there's any strong evidence of long term effects.