In our consideration of scientific literature about the impact of sexual abuse, a very interesting point is the comparison of the impact of sexual abuse with other types of abuse and neglect, especially physical and psychological abuse and physical and emotional neglect.
First, this comparison supports the position that the harm caused by "sexual abuse" is highly overexaggerated in the public opinion. This is possible because many people have some expectations about the harm caused by typical physical abuse, but no experience with sexual abuse. If there exists some comparison between physical and sexual abuse, this allows a much better judgement about the seriousness of the harm caused by sexual abuse.
For this purpose, we can use, for example, Richter-Appelt 1994 (in German). The advantage of this paper is that it contains a description of the criteria used for sexual and physical abuse, and considers a lot of very different types of impact. Sexual abuse was defined as an unwanted sex involving physical contact, and for physical abuse it was necessary to mention something like "slaps in the face" regularly, or a serious form of abuse once. The resulting negative impact was comparable, and for the majopity of problems even worse for physical abuse.
But this is not the only implicit information we can extract from a comparison with other types of abuse. If the same impact may be caused as by sexual, as by physical abuse, it is highly probable that there is a common causal explanation of this association.
Such a common causal explanation may be based on something different (like social status, family problems) which makes as physical, as sexual abuse more probable. Such explanations does not falsify our hypothesis that volitional sex does not cause harm.
The other possibility is that there is something common between sexual and physical abuse which causes the harm. Now, there is an obvious candidate for this common aspect - the trauma caused by an unwanted, adverse experience. Again, this causal explanation is in agreement with our hypothesis that volitional sex does not cause harm.
Thus, the observation that similar negative impact may be caused by other traumatic childhood experiences too is indirect evidence for our hypothesis.