[WOLFGIR]

Yes you can by adding a correction layer.
In the layer palette you have a circle which if pressed down, will give you several options to add a new correction layer. Add a correction layer that changes they brightness/contrast for instance. It will change all the layers beneath it. If you have layers you don't want to be changed by this new layer, for instance a background. Add a new "set" a folder in the layer pallete, move the correction layer and the layers to be corrected into that folder called a set.

Voila.