This system of apprenticeship and informal adoption extended into the 19th century, today seen as a transitional phase for adoption history. Under the direction of social welfare activists, orphan asylums began to promote adoptions based on sentiment rather than work; children were placed out under agreements to provide care for them as family members instead of under contracts for apprenticeship.[21] The growth of this model is believed to have contributed to the enactment of the first modern adoption law in 1851 by the Commonwealth of Massachusetts, unique in that it codified the ideal of the "best interests of the child."[22][23] Despite its intent, though, in practice, the system operated much the same as earlier incarnations. The experience of the Boston Female Asylum (BFA) is a good example, which had up to 30% of its charges adopted out by 1888.[24] Officials of the BFA noted that, although the asylum promoted otherwise, adoptive parents did not distinguish between indenture and adoption; "We believe," the asylum officials said, "that often, when children of a younger age are taken to be adopted, the adoption is only another name for service."[25]
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.[167]
The biological relationship between a parent and child is important, and the separation of the two has led to concerns about adoption. The traditional view of adoptive parenting received empirical support from a Princeton University study of 6,000 adoptive, step, and foster families in the United States and South Africa from 1968 to 1985; the study indicated that food expenditures in households with mothers of non-biological children (when controlled for income, household size, hours worked, age, etc.) were significantly less for adoptees; step-children, and foster children, causing the researchers to speculate that, instinctively, people are less interested in sustaining the genetic lines of others.[92] This theory is supported in another more qualitative study where in adoptive relationships marked by sameness in likes, personality, and appearance, both adult adoptees and adoptive parents report being happier with the adoption.[93]
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).[135] 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.[136]
Foster care adoption: this is a type of domestic adoption where a child is initially placed in public care. Many times the foster parents take on the adoption when the children become legally free. Its importance as an avenue for adoption varies by country. Of the 127,500 adoptions in the U.S. in 2000[83] about 51,000 or 40% were through the foster care system.[84]
Previous research on adoption has led to assumptions that indicate that there is a heightened risk in terms of psychological development and social relationships for adoptees. Yet, such assumptions have been clarified as flawed due to methodological failures. But more recent studies have been supportive in indicating more accurate information and results about the similarities, differences and overall lifestyles of adoptees.[125]
More recent research found that in a sample of mothers who had released their children for adoption four to 12 years prior, every participant had frequent thoughts of their lost child. For most, thoughts were both negative and positive in that they produced both feelings of sadness and joy. Those who experienced the greatest portion of positive thoughts were those who had open, rather than closed or time-limited mediated adoptions.[123]
Although adoption is often described as forming a "forever" family, the relationship can be ended at any time. The legal termination of an adoption is called disruption. In U.S. terminology, adoptions are disrupted if they are ended before being finalized, and they are dissolved if the relationship is ended afterwards. It may also be called a failed adoption. After legal finalization, the disruption process is usually initiated by adoptive parents via a court petition and is analogous to divorce proceedings. It is a legal avenue unique to adoptive parents as disruption/dissolution does not apply to biological kin, although biological family members can be disowned or abandoned.[91]

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.
Identity is defined both by what one is and what one is not. Adoptees born into one family lose an identity and then borrow one from the adopting family. The formation of identity is a complicated process and there are many factors that affect its outcome. From a perspective of looking at issues in adoption circumstances, the people involved and affected by adoption (the biological parent, the adoptive parent and the adoptee) can be known as the "triad members and state". Adoption may threaten triad members' sense of identity. Triad members often express feelings related to confused identity and identity crises because of differences between the triad relationships. Adoption, for some, precludes a complete or integrated sense of self. Triad members may experience themselves as incomplete, deficient, or unfinished. They state that they lack feelings of well-being, integration, or solidity associated with a fully developed identity.[129]

"Honest Adoption Language" refers to a set of terms that proponents say reflect the point of view that: (1) family relationships (social, emotional, psychological or physical) that existed prior to the legal adoption often continue past this point or endure in some form despite long periods of separation, and that (2) mothers who have "voluntarily surrendered" children to adoption (as opposed to involuntary terminations through court-authorized child-welfare proceedings) seldom view it as a choice that was freely made, but instead describe scenarios of powerlessness, lack of resources, and overall lack of choice.[187][188] It also reflects the point of view that the term "birth mother" is derogatory in implying that the woman has ceased being a mother after the physical act of giving birth. Proponents of HAL liken this to the mother being treated as a "breeder" or "incubator".[189] Terms included in HAL include terms that were used before PAL, including "natural mother," "first mother," and "surrendered for adoption."

As the idea of institutional care gained acceptance, formal rules appeared about how to place children into families: boys could become apprenticed to an artisan and girls might be married off under the institution's authority.[19] Institutions informally adopted out children as well, a mechanism treated as a way to obtain cheap labor, demonstrated by the fact that when the adopted died, their bodies were returned by the family to the institution for burial.[20] 

Adoptions can occur either between related family members, or unrelated individuals. Historically, most adoptions occurred within a family. The most recent data from the U.S. indicates about half of adoptions are currently between related individuals.[78] A common example of this is a "stepparent adoption", where the new partner of a parent may legally adopt a child from the parent's previous relationship. Intra-family adoption can also occur through surrender, as a result of parental death, or when the child cannot otherwise be cared for and a family member agrees to take over.

Other studies provide evidence that adoptive relationships can form along other lines. A study evaluating the level of parental investment indicates strength in adoptive families, suggesting that parents who adopt invest more time in their children than other parents and concludes, "...adoptive parents enrich their children's lives to compensate for the lack of biological ties and the extra challenges of adoption."[94] Another recent study found that adoptive families invested more heavily in their adopted children, for example, by providing further education and financial support. Noting that adoptees seemed to be more likely to experience problems such as drug addiction, the study speculated that adoptive parents might invest more in adoptees not because they favor them, but because they are more likely than genetic children to need the help.[95]
Other ancient civilizations, notably India and China, used some form of adoption as well. Evidence suggests the goal of this practice was to ensure the continuity of cultural and religious practices; in contrast to the Western idea of extending family lines. In ancient India, secondary sonship, clearly denounced by the Rigveda,[12] continued, in a limited and highly ritualistic form, so that an adopter might have the necessary funerary rites performed by a son.[13] China had a similar idea of adoption with males adopted solely to perform the duties of ancestor worship.[14]
The language of adoption is changing and evolving, and since the 1970s has been a controversial issue tied closely to adoption reform efforts. The controversy arises over the use of terms which, while designed to be more appealing or less offensive to some persons affected by adoption, may simultaneously cause offense or insult to others. This controversy illustrates the problems in adoption, as well as the fact that coining new words and phrases to describe ancient social practices will not necessarily alter the feelings and experiences of those affected by them. Two of the contrasting sets of terms are commonly referred to as positive adoption language (PAL) (sometimes called respectful adoption language (RAL)), and honest adoption language (HAL).

Family plays a vital role in identity formation. This is not only true in childhood but also in adolescence. Identity (gender/sexual/ethnic/religious/family) is still forming during adolescence and family holds a vital key to this. The research seems to be unanimous; a stable, secure, loving, honest and supportive family in which all members feel safe to explore their identity is necessary for the formation of a sound identity. Transracial and International adoptions are some factors that play a significant role in the identity construction of adoptees. Many tensions arise from relationships built between the adoptee(s) and their family. These include being "different" from the parent(s), developing a positive racial identity, and dealing with racial/ethnic discrimination.[130] It has been found that multicultural and transnational youth tend to identify with their parents origin of culture and ethnicity rather than their residing location, yet it is sometimes hard to balance an identity between the two because school environments tend to lack diversity and acknowledgment regarding such topics.[131] These tensions also tend to create questions for the adoptee, as well as the family, to contemplate. Some common questions include what will happen if the family is more naïve to the ways of socially constructed life? Will tensions arise if this is the case? What if the very people that are supposed to be modeling a sound identity are in fact riddled with insecurities? Ginni Snodgrass answers these questions in the following way. The secrecy in an adoptive family and the denial that the adoptive family is different builds dysfunction into it. "... social workers and insecure adoptive parents have structured a family relationship that is based on dishonesty, evasions and exploitation. To believe that good relationships will develop on such a foundation is psychologically unsound" (Lawrence). Secrecy erects barriers to forming a healthy identity.[132]

These differences in development appear to play out in the way young adoptees deal with major life events. In the case of parental divorce, adoptees have been found to respond differently from children who have not been adopted. While the general population experienced more behavioral problems, substance use, lower school achievement, and impaired social competence after parental divorce, the adoptee population appeared to be unaffected in terms of their outside relationships, specifically in their school or social abilities.[117]
There are supporters of various lists, developed over many decades, and there are persons who find them lacking, created to support an agenda, or furthering division. All terminology can be used to demean or diminish, uplift or embrace. In addressing the linguistic problem of naming, Edna Andrews says that using "inclusive" and "neutral" language is based upon the concept that "language represents thought, and may even control thought."[190]