Background. Increased risks of severe psychiatric psychopathology (suicide, parasuicide, psychiatric hospital care) and serious social disturbances (addiction, criminality) have been demonstrated. The academic achievement of adoptees is lower than that of peers from similar SES circumstances. This raises the question whether limited cognitive capacity may have contributed to the psychosocial symptoms. Previously, a link has been established between cognitive capacity and risks of parasuicide and schizophrenia.

The aims are to search for possible mechanisms underlying such over-risks, with the further aim of creating preventive and therapeutic interventions. Main questions. Are there - at a group level - differences in cognitive capacity between inter-country adoptees, national adoptees and non-adoptees? May such differences explain differences in risks of developing severe psychosocial symptoms?

Information about results from cognitive tests performed in military enlistment examinations on all men born 1951-1976 who had undergone military conscription between 1969 and 1994 (appr. 1,000,000 individuals), was obtained from the Military Service Conscription Register.