It doesn't seem like they show evidence for anything more than significant correlation. Other theories (like birth trauma reduction) could explain it just as well.
This thread is a good example of why I don't usually comment on YC. People don't take the discussions seriously enough. They ask a question and don't followup. It's not worth explaining things carefully here.
Web forums need better notification when someone responds to you. And each site has to reinvent the wheel. I remember people asked for this for months on reddit before it got the little envelope icon.
