If depressed, your pet has probably lost the appetite and thus he is rejecting any food.
Signs that a rabbit may be suffering from stress/fear/depression can be fairly obvious sometimes but some rabbit behaviour of this nature is difficult to spot. Here are some basic signs to watch out for:
Hiding
Chewing cage bars
Over-grooming
Altered feeding habits
Different toilet habits
Over-drinking
Sitting hunched
A reluctance to move
Repeated circling
Some rabbits are just very calm and not overly active. "Chill" I guess you could say. Rabbits like to hide away sometimes, however, if your rabbit is hiding all the time, even at their most active times of the day (early morning and dusk), then it could be a sign that something is wrong.
Maybe if you gave more details on why you think your rabbit is stressed/depressed, you'd be able to receive more help?