Treatment of depression faces two main challenges. The first is that almost 50% of patients do not respond well to existing antidepressants. The second is that conventional medications take a relatively long time—around three to five weeks—to have the desired effect. A group of researchers affiliated with the University of São Paulo (USP) in Brazil set out to tackle the second problem by using epigenetic modulators to try to “erase” the consequences of stress. Epigenetic mechanisms are part of a complex system that controls how and when genes are switched on or off.