Nobody denies that nonconsensual sexual experiences may be harmful for the children involved. There are a lot of descriptions of such abusive experiences which show such negative outcome. And there are a lot of investigations which show a statistical correlation between childhood sexual abuse and various negative outcome.
On the other hand, there is a widely distributed opinion that scientific research has shown also that even consensual childhood sexual experiences are often harmful and highly dangerous. But this seems to be not correct. In addition, the probability and severity of the negative impact of sexual abuse seems overrated, and the role of other factors instead of sexual abuse seems often underestimated.
I have started to look into the related "sexual abuse" literature with the aim to verify these assumtions. My literature research is far from being complete, but up to now in coincidence with the assumption that consensual sex is not harmful (see a summary of the results below).
Let's start with the results collected by David Finkelhor:
For me, the aim of this research is not only to verify, that there are really no results which establish harm caused by consensual experiences (this has been done already by other researchers), but to allow you to verify this by yourself without going into the library.
I hope, this will be useful not only for people who want to find out if and which harm may be caused by consensual sexual relations, but also by others, like victims of real child abuse who want to find information about possible lasting effects.
I recognize that I have a personal bias - I'm not interested in finding
results which show damage caused by consensual sexual experiences. To
minimize the influence of this bias on the results, I try to include a lot
of the text of the original, and at least the abstract of every relevant
paper. This requires a lot of time, much more than simply to verify for
myself that there are no "critical" results in a given paper. That's why at
the current moment only a small number or papers has been included. But I
have not "selected" between "good" and "bad" papers. I know, I cannot prove
this until I have included them all, but I hope you believe me in this
point.
Summary
There is a lot of literature in this domain, and I have not so much
time as I want to spend for this. But already at the current state it
seems possible to summarize:
Negative outcome is mostly found only for women. Considering the fact that coercion and violence is much more common in man/girl relationships compared with man/boy relationships, this gives additional evidence that only the nonconsensual experiences cause the problems.