If one feels unhappy about the causality link between a good childhood and a better life as an adult please remember that we are talking about statistical effects here. If more people who were bullied end up in unfortunate positions that doesn't imply direct causality, it implies that people whose live paths lead to bad places often had being bullied as a station on it.
There will always be the tail ends of the statistical function, so people who became phenomenal adults despite all hardships, but also people who had a good childhood and became utterly disfunctional adults. But if we think about devising utilitarian political measures knowing what "broadly" has an effect on people is useful. Ideally you discover small things that if changed would have huge positive downstream effects. E.g. if bullying would be shown to have a big impact on later lives, it could be justified to pick up more funds to prevent it, to help victims and/or to change the way schools work in order to minimize chances someone is being bullied. Bullying is just an example, one could also pick other triggers.
There will always be the tail ends of the statistical function, so people who became phenomenal adults despite all hardships, but also people who had a good childhood and became utterly disfunctional adults. But if we think about devising utilitarian political measures knowing what "broadly" has an effect on people is useful. Ideally you discover small things that if changed would have huge positive downstream effects. E.g. if bullying would be shown to have a big impact on later lives, it could be justified to pick up more funds to prevent it, to help victims and/or to change the way schools work in order to minimize chances someone is being bullied. Bullying is just an example, one could also pick other triggers.