The evacuation of civilians has been performed in many countries in times of war. The evacuation of civilians in Britain immediately after the outbreak of the Second World War was designed to save children from the risks associated with aerial bombing of cities by moving them to areas thought to be less at risk. Operation Pied Piper, which began on 1 September 1939, officially relocated more than 3.5 million people.

In Germany there was no large scale evacuation of civilians as there was in Britain. The German term used for the evacuation of children was Kinderlandverschickung, to avoid the term evacuation.

Evacuation also occurred in other countries. Some 70 000 children were evacuated from Finland, chiefly to Sweden, but also to Norway and Denmark.

This only got a lot of attention after a film in 2005, Mother of Mine by the award winning director Klaus Härö, which tackles that painful patch of history in the tale of 9 year old Eero, a child who increasingly feels abandoned by his biological Finnish mother, and yet who’s not attached to his Swedish surrogate mom. When he is returned to Finland, his confusion intensifies.

This film was followed by a public discussion wondering if the evacuation can be considered psychologically flawed, as the separations may have inflicted a greater damage on the evacuees than the damage suffered by those children who had remained with their parents in Finland.

This topic has now been addressed by Torsten Santavirta and colleagues. They performed a cohort study including 45 463 children born in Finland between 1933 and 1944. Evacuees in the sample were identified from war time government records.

The authors report that the Finnish evacuation policy was not associated with an increased overall risk of admission to hospital for a psychiatric disorder in adulthood among former evacuees. In fact, evacuation was associated with a marginally reduced risk of admission for any psychiatric disorder among men. Among women who had been evacuated, however, the risk of being admitted to hospital for a mood disorder was increased.

These gender differences aren’t easy to interpret. In an accompanying editorial, Derrick Silove highlights that maintaining the integrity of families should be a cornerstone of policies to protect children in war zones.

Georg Roeggla is an associate editor for The BMJ.