[...] There’s actually lots of ways to “infect” a rat with depression, though some are more efficient than others. A frequently cited 1992 paper reviewing the best methods concludes that you don’t actually want to traumatize or terrify your rats, like Selye accidentally did. The closest approximation of the depression that plagues modern humans can be achieved by bombarding lab rats with mild but chronic, random, and inescapable stress. You don’t have to terrify them—just remove predictability and control from their lives, and they’ll eventually lose interest in pleasurable things. When they do, you’re ready to test whether your experimental antidepressant will get them interested again.