The number of adoptions in the United States peaked in 1970.[45] It is uncertain what caused the subsequent decline. Likely contributing factors in the 1960s and 1970s include a decline in the fertility rate, associated with the introduction of the pill, the completion of legalization of artificial birth control methods, the introduction of federal funding to make family planning services available to the young and low income, and the legalization of abortion. In addition, the years of the late 1960s and early 1970s saw a dramatic change in society's view of illegitimacy and in the legal rights[46] of those born outside of wedlock. In response, family preservation efforts grew[47] so that few children born out of wedlock today are adopted. Ironically, adoption is far more visible and discussed in society today, yet it is less common.[48]
In Spain under Francisco Franco’s 1939–75 dictatorship the newborns of some left-wing opponents of the regime, or unmarried or poor couples, were removed from their mothers and adopted. New mothers were frequently told their babies had died suddenly after birth and the hospital had taken care of their burials, when in fact they were given or sold to another family. It is believed that up to 300,000 babies were involved. These system – which allegedly involved doctors, nurses, nuns and priests – outlived Franco’s death in 1975 and carried on as an illegal baby trafficking network until 1987 when a new law regulating adoption was introduced.[180][181]
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]

Nevertheless, work on adult adoptees has found that the additional risks faced by adoptees are largely confined to adolescence. Young adult adoptees were shown to be alike with adults from biological families and scored better than adults raised in alternative family types including single parent and step-families.[137] Moreover, while adult adoptees showed more variability than their non-adopted peers on a range of psychosocial measures, adult adoptees exhibited more similarities than differences with adults who had not been adopted.[138] There have been many cases of remediation or the reversibility of early trauma. For example, in one of the earliest studies conducted, Professor Goldfarb in England concluded that some children adjust well socially and emotionally despite their negative experiences of institutional deprivation in early childhood.[139] Other researchers also found that prolonged institutionalization does not necessarily lead to emotional problems or character defects in all children. This suggests that there will always be some children who fare well, who are resilient, regardless of their experiences in early childhood.[140] Furthermore, much of the research on psychological outcomes for adoptees draws from clinical populations. This suggests that conclusions such that adoptees are more likely to have behavioral problems such as ODD and ADHD may be biased. Since the proportion of adoptees that seek mental health treatment is small, psychological outcomes for adoptees compared to those for the general population are more similar than some researchers propose.[141]
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]