Private domestic adoptions: under this arrangement, charities and for-profit organizations act as intermediaries, bringing together prospective adoptive parents and families who want to place a child, all parties being residents of the same country. Alternatively, prospective adoptive parents sometimes avoid intermediaries and connect with women directly, often with a written contract; this is not permitted in some jurisdictions. Private domestic adoption accounts for a significant portion of all adoptions; in the United States, for example, nearly 45% of adoptions are estimated to have been arranged privately.
The adoptee population does, however, seem to be more at risk for certain behavioral issues. Researchers from the University of Minnesota studied adolescents who had been adopted and found that adoptees were twice as likely as non-adopted people to suffer from oppositional defiant disorder and attention-deficit/hyperactivity disorder (with an 8% rate in the general population). Suicide risks were also significantly greater than the general population. Swedish researchers found both international and domestic adoptees undertook suicide at much higher rates than non-adopted peers; with international adoptees and female international adoptees, in particular, at highest risk.
Embryo adoption: based on the donation of embryos remaining after one couple's in vitro fertilization treatments have been completed; embryos are given to another individual or couple, followed by the placement of those embryos into the recipient woman's uterus, to facilitate pregnancy and childbirth. In the United States, embryo adoption is governed by property law rather than by the court systems, in contrast to traditional adoption.
Evidence about the development of adoptees can be supported in newer studies. It can be said that adoptees, in some respect, tend to develop differently from the general population. This can be seen in many aspects of life, but usually can be found as a greater risk around the time of adolescence. For example, it has been found that many adoptees experience difficulty in establishing a sense of identity.
Similar mechanisms appear to be at work in the physical development of adoptees. Danish and American researchers conducting studies on the genetic contribution to body mass index found correlations between an adoptee's weight class and his biological parents' BMI while finding no relationship with the adoptive family environment. Moreover, about one-half of inter-individual differences were due to individual non-shared influences.
Europe's cultural makeover marked a period of significant innovation for adoption. Without support from the nobility, the practice gradually shifted toward abandoned children. Abandonment levels rose with the fall of the empire and many of the foundlings were left on the doorstep of the Church. Initially, the clergy reacted by drafting rules to govern the exposing, selling, and rearing of abandoned children. The Church's innovation, however, was the practice of oblation, whereby children were dedicated to lay life within monastic institutions and reared within a monastery. This created the first system in European history in which abandoned children did not have legal, social, or moral disadvantages. As a result, many of Europe's abandoned and orphaned children became alumni of the Church, which in turn took the role of adopter. Oblation marks the beginning of a shift toward institutionalization, eventually bringing about the establishment of the foundling hospital and orphanage.
In many jurisdictions the adopted person's full original birth certificate is cancelled and replaced with a fabricated post-adoption birth certificate which states that the child was born to the adoptive parents. This deception, when carried out, may continue with the adopted person for life and can be the cause for many well documented traumas experienced by the adopted person, including loss of identity, family history, culture, biological family (including not only biological parents but also siblings and extended family), family medical history and records, and increased risk of suicide, homelessness, incarceration, PTSD, depression, and anxiety.
Externally focused theories, in contrast, suggest that reunion is a way for adoptees to overcome social stigma. First proposed by Goffman, the theory has four parts: 1) adoptees perceive the absence of biological ties as distinguishing their adoptive family from others, 2) this understanding is strengthened by experiences where non-adoptees suggest adoptive ties are weaker than blood ties, 3) together, these factors engender, in some adoptees, a sense of social exclusion, and 4) these adoptees react by searching for a blood tie that reinforces their membership in the community. The externally focused rationale for reunion suggests adoptees may be well adjusted and happy within their adoptive families, but will search as an attempt to resolve experiences of social stigma.
Markedly different from the modern period, ancient adoption practices put emphasis on the political and economic interests of the adopter, providing a legal tool that strengthened political ties between wealthy families and created male heirs to manage estates. The use of adoption by the aristocracy is well documented; many of Rome's emperors were adopted sons. Adrogation was a kind of Roman adoption which required the adrogator to be at least 60 years old.
The stigmas associated with adoption are amplified for children in foster care. Negative perceptions result in the belief that such children are so troubled it would be impossible to adopt them and create "normal" families. A 2004 report from the Pew Commission on Children in Foster Care has shown that the number of children waiting in foster care doubled since the 1980s and now remains steady at about a half-million a year."
Infant adoption during Antiquity appears rare. Abandoned children were often picked up for slavery and composed a significant percentage of the Empire's slave supply. Roman legal records indicate that foundlings were occasionally taken in by families and raised as a son or daughter. Although not normally adopted under Roman Law, the children, called alumni, were reared in an arrangement similar to guardianship, being considered the property of the father who abandoned them.