So, it seems it's permanent?
Insanity it mentions as costing 100xp to remove, which was the same cost as in Deathwatch as well, but there you could also remove corruption. Though with their apothecarys and special nature, it isn't impossible this is just for them.
In only war, in the rules section of these things it mentions the 100xp to remove insanity, but nothing about removing corruption… Not sure if it's meant to be like that or just missed a rule. Anyone know?