Early life stress (ELS), an experience of severe stress due for example to parental loss, abuse or neglect during the childhood years, may have profound long-term effects on the individual's physiology and psychology. Here we review the findings of the Helsinki Birth Cohort Study 1934-44 (n=13,345), of whom approximately 14% were temporarily separated from both their parents due to child evacuations in World War II. The children were evacuated from Finland, unaccompanied by their parents, to other countries in Scandinavia (Sweden and Denmark) at the average age of 4.7 years (SD=2.4 years) and for an average period of 1.7 years (SD=1.0 years). Information on these separations for each member of the HBCS was derived from the Finnish National Archives. We found significant effects of ELS on psychiatric morbidity and mortality, intellectual ability, stress reactivity, reproductive history, and inter-generational social mobility.