Danish and American researchers conducting studies on the genetic contribution to body mass index found correlations between an adoptees 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.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.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 develop oppositional defiant disorder (ODD) and attention deficit hyperactivity disorder (ADHD), 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.Nevertheless, work on adult adoptees has found that the additional risks faced by adoptees are largely confined to adolescence.
Although there are a range of reasons, the most recent study of experiences of women who adopt suggests they are most likely to be 40–44 years of age, to be currently married, to have impaired fertility, and to be childless.Unrelated adoptions may occur through the following mechanisms:

Private domestic adoptions: under this arrangement, charities and for-profit organizations act as intermediaries, bringing together prospective adoptive parents with 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. 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, about 51,000 or 40% were through the foster care system. International adoption: this involves the placing of a child for adoption outside that childs country of birth. This can occur through public or private agencies. In some countries, such as Sweden, these adoptions account for the majority of cases (see above table).