Each to their own and whatever you feel comfortable with is right for you and your dc.
On the studies point, I worry because women do release oxytocin when they sleep with a man causing them to fall in love and ime it can be very distracting and overwhelming, especially for a young teen, and that is aside from the risks of pregnancy and stds. I’ve seen it happen in extended family. But it also depends on the individual personality, and self confidence of the girl too.
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And to make more general points:
In addition to oxytocin, sex creates a lot of emotion to deal with in teen girls whose confidence and emotions are often all over the place anyway.
And it’s a lot of pressure for young teen girls to deal with the expectations of sexual intimacy at such a young age when they may not yet have the self esteem to put in boundaries that they are comfortable with and they say “yes” when they mean “no”.
Even the nicest, politest boys from good homes can create unwanted pressure “in the moment”.
Also, many boys nowadays from “naice” homes are learning about sex from You Tube and porn.
Call me sexist but the stakes just aren’t as high for young lads so maybe I would feel differently if I had boys?
But these are my personal reasons for not encouraging or supporting sex below the age of college or uni years, by which time, hopefully, teens are more equipped to look after themselves and have more self confidence to instigate boundaries if they need to.
Until then, I am happy to be unpopular and be called a prude (which I am not) and create some of those boundaries on their behalf. Hopefully they will thank me later.