What are the effects of hebephilia? Following the Milo Yiannopoulos shebang, I had a discussion with a friend over the effects of a sexually maturing teenager (14ish) engaging in sexual behavior with a significantly older adult (at least 23 years old). In the discussion we both realized that in fact we were just spewing opinions at each-other, and in reality couldn't point to a fair study showing either the negative or positive effects of such practice. So, I am wondering "are there any fair studies exploring the effects?". (I believe that societal sentiment toward such behavior will sway the "victim's" feelings toward the experience, and hopefully the studies will somehow control for that)
I thought I would edit to add a bit of information.  First of all for those who don't know, (I didn't until I looked it up when I saw this question for the first time), the term hebephilia has been proposed to split pedophilia and denote the erotic preference for pubescent children (roughly, ages 11 or 12-14), but it has not become widely used. Along with hebephilia, there is also Pedohebephilia which is erotic preference on both pedophilic and hebephilic levels.

I would also like to address the issue of Milo Yiannopoulos who seems to have been a topic of discussion, which raised this question.  In the Wikipedia page I linked here and in my edit of the OPs question, it says:


  Yiannopoulos stated that sexual relationships between 13-year-old boys and adults can be "perfectly consensual," because some 13-year-olds are, in his view, sexually and emotionally mature enough to consent to sex with adults; he spoke favourably both of gay 13-year-old boys having sex with adult men and straight 13-year-old boys having sex with adult women. (Source 1) (Source 2) He used his own experience as an example, saying he was mature enough to be capable of giving consent at a young age.


The page also states that


  Defending himself in a press conference, Yiannopoulos alleged that he had been the victim of child abuse, and that "his comments were a way to cope with it".


I am not going to enter into any debate or express any opinion on what Yiannopoulos said or didn't say — or even what he may have been trying to say — as this is not the forum to do this, but speaking from the standpoint of someone who has, over a period of over 17 years, supported many who have been sexually abused and raped, I can categorically say that different people use many different ways to "cope" with the effects of the past events.  Was he using repression or projection as an ego-defence mechanism? It's difficult to say.

I have been drafting my answer and editing the draft many times in order to make sure I try not to add anything which might inflame the already heated debate over Yiannopoulos, so here goes.

The question raised here is


  Are there any fair studies exploring the effects of a sexually maturing teenager (14ish) engaging in sexual behavior with a significantly older adult (at least 23 years old)?


In The Journal of Criminal Law and Criminology there is an article which examines behavioural scientific research on the subject (McCord, D. 1986).


  A researcher reviewing the literature on the subject, came to the conclusion that little had been learned about child sexual abuse during the preceding twenty-five years.  He also noted that the literature dealing with the sexual abuse of minors, was "scant, unintegrated, and ambiguous. Books on the topic are rare. Articles are scattered and hidden among a wide range of journals, many in non-accessible medical and legal journals."
  
  One reason for the lack of solid research is simply that the subject is a very difficult one to study. Only a small percentage of cases is ever reported. In those cases that are reported, the participants are often reluctant to discuss the situation. As a result of problems like these there are methodological difficulties virtually built into most research projects in the area.


Comments from research state the following


"Children can exhibit the entire gamut of behaviors in response to a sexual assault, ranging from the negative to the positive." (Burgess, et al., 1978)
"Children's immediate reactions to an assault vary." (Leaman, 1980)
"Incest victims show a wide variety of symptom complaints or may show none at all." (Stuart &amp; Greer, 1984; Sgroi, 1975)
"Even those professionals who have a clinical definition with which they are comfortable will still have problems in identifying sexually abused children." (Mrazek, 1987)


The reason that such a wide variety of symptoms has been noted is that child sexual abuse is very complex situation from the point of view of the victim.  This can perhaps best be illustrated by comparing it with adult rape, which is, by contrast, very unambiguous from the victim's perspective. In adult rape the victim is often but not always coerced by physical force or threats of physical force to engage in sexual activity which he or she does not desire. Under these circumstances, even when there is no physical violence, or threat of physical violence, there is no possibility of the victim enjoying the activity or emerging from the situation with any positive psychological emotions, as consent has not been given. Accordingly, it is not surprising that the reactions of adult victims to forcible rape are remarkably similar to each other and are drastically negative. By contrast, a child sexual abuse victim's feelings may be, and often are, ambivalent. The victim's will is usually much more malleable than an adult's, particularly when the perpetrator may be assuring the child that the activity is normal and even possibly suggesting that it is teaching them what they need to know.

Another point of note which can cause problems for the child in later life is that, although not in all cases, the child may even feel physical pleasure during the activity. As one researcher put it:


  Contrary to the stereotype, most victims in our study readily acknowledged the positive as well as the negative elements of their experience. They talked about the times the physical sensations felt good, or they remembered how their sexual experience with an adult or family member satisfied a longing for affection and closeness that was rarely met at any other time. (Finkelhor, 1981)


While this researcher found that 60% of adult women who had been sexually abused as children remembered the experience as primarily negative, only 7% remembered it as primarily positive.

The effects of statutory rape, and childhood sexual abuse is complex and whether or not it may be perceived to be consensual, it is generally believed that informed consent cannot be given by someone under the legal age of consent. (Abel, et al., 1984).

References

Abel, G. G., Becker, J. V., Cunningham-Rathner, J., 1984. Complications, Consent, and Cognitions in Sex Between Children and Adults. International Journal of Law and Psychiatry, 7(1), pp. 69-103. http://dx.doi.org/10.1016/0160-2527(84)90008-6

Burgess, A. W., Groth, N. A., Holmstrom, L. L., &amp; Sgroi, S. M., 1978. Sexual assault of children and adolescents. Lexington, MA: D.C. Health.

Finkelhor, D., 1981. Sexually victimized children. New York, NY: Free Press; London: Collier Macmillan.

Leaman, K. M., 1980. Sexual abuse : the reactions of child and family in U.S. Dept. of Health and Human Services, Sexual Abuse of Children: Selected Readings.

Mrazek, P. B., 1987. Definition and recognition of sexual child abuse: historical and cultural perspectives in Sexually abused children and their families. Oxford; New York: Pergamon Press.

McCord, D., 1985. Expert Psychological Testimony about Child Complainants in Sexual Abuse Prosecutions: A Foray into the Admissibility of Novel Psychological Evidence. The Journal of Criminal Law and Criminology, 77(1), pp. 1-68.
Available Free from: http://scholarlycommons.law.northwestern.edu/jclc/vol77/iss1/1/

Sgroi, S. M., 1975. Sexual Molestation of Children: The Last Frontier in Child Abuse, Children Today, 4(3) pp. 18-21.

Stuart, I. R., Greer, J. G, 1984. Victims of Sexual Aggression: Treatment of Children, Women, and Men. Publisher: Chapman &amp; Hall.