There's a natural "bedtime shift" of 1-3h in adolescence, that doesn't mean it's natural for them to still be asleep when the sun is up. The one thing that dis

There's a natural "bedtime shift" of 1-3h in adolescence, that doesn't mean it's natural for them to still be asleep when the sun is up. The one thing that disrupts the circadian rhythm dramatically is light. This is well-established and also mentioned in the article you linked.