no since the you would have to take in other factors that would affect that if an Amish person or one living oversees. For data like this you would have to quite literally clone these people , take away when they got a cellphone to be absolutely certain that getting a phone at the young age is the reason.

Amish have a whole different societal structure so it's too much variation. Same issue if you study Indians in a remote village for instance. That would make a poor control group to compare to teenage girls going to high school in Texas.