By "real" I'm assuming you mean something like "a phenomenon that needs to be accounted for in order to make accurate predictions". Specifically, predictions about what people will do. If so, absolutely.

Of course then there are other valid senses of "real" which everyone else is arguing below, in which there is the question of effects outside people's actions, and whether the phenomenon showed up in people's heads because an entity outside our scientific understanding called God put it there. Those are, of course, the tricky ones.

(God of the Gaps time!)