dehumanization

Adoptees face challenges including poor ownership by foster parents, poor understanding with foster parents and poor acceptance in the society

You are better off doing your own literature search here. I recommend getting a few key papers and putting them into ResearchRabbit as a way of fleshing out the literature.

This question is too broad to attract an indepth answer here. You just get nonsense like @safder up there, who goes round with his buddies recommending their rubbish answers.

Our son is adopted. No big deal. But we live in Northern Virginia, not rural Virginia, USA, where it might be different. Of course, I would expect a mix of attitudes everywhere. Anyway, at one time I was in a hospital waiting room, or some similar venue, and I heard someone loudly proclaiming "He ain't no kin [relationship]! He ain't no kin! He's adopted!" I was shocked at this. I do not know who said that, to whom, about whom, or what was the topic, but it was, in a word, shocking.  I think that was the late 20th century.  About that time, however, I ran into someone on a train, I think it was, who had the opposite attitude and had also adopted.

Recently, another attendee at a statistics conference has told me that he was adopted.

It seems to me that the people who are not well adjusted are the people who think there is something odd about adoption.

For adoptees, their confidence in their own identities has to be influenced by the attitudes of those they encounter. As with everything else, each individual is different and has his/her own strengths and weaknesses.  But if they grow up with a positive attitude, being told their origins, well, our son is a really good person. 

But being a statistician, I know that anecdotes are only possibilities and no substitute for a scientific study, and people's experiences can differ.  What seems logical and common sense may not be the whole story.  But in my experience, people can have wildly different attitudes. 

As Ronán said, you need a "literature search."  It can still be tricky. It depends on the way each study was conducted.  Even a good probability sample study of this could be flawed.  For example, I used to get questionnaires because I have a twin sister, and there was a long term twin study.  But the questionnaire was so very long and full of psychologically-related questions that seemed unanswerable (like "have you stopped robbing banks") that I finally refused to even attempt to fill them out anymore. 

My last point here is that you need to know how a study was conducted to judge the merits of the results. 

Best Wishes - Jim Knaub