I think that any animal at a shelter tends to be stressed, for several reasons. Typically, conditions are crowded, full of strange people constantly looking in at them, strange smells, and endless noise...barking of dogs and cats crying out. In a world where most of these animals once knew stability and familiarity, that is taken away from them and they are thrust into an alien environment without any understanding of why. They seem to sense what is going on, and will try their best to be noticed...it is almost as if they know that if they get the attention, someone will take heart and give them a new home. As time passes, if the dog or cat (or rabbit) is constantly passed up for another, they become withdrawn and will actually fall into a depressed state. If you've ever seen the look on an animal's face that has been in this situation, you will actually recognize that they are giving up hope. It is the most heartbreaking thing to see.
As for rabbits being depressed at home, well...I suspect that a rabbit who is truly depressed will show it by sitting in a corner, not showing much enthusiasm for food or for life in general. They will seem *off*, not themselves at all. But from what I've seen from rabbits I've had over the years, and read of most of the rabbits owned by people here, they are all fairly happy, healthy bunnies. Throughout this winter I've been keeping Raph in the house, and at first wondered about his mental welfare as he has to be confined to a dog crate during the day. But as I've watched him over the weeks, it seems to me he is a pretty happy rabbit. When I come home from work I open the crate door and he eases his way out, stretching his body and legs. Then he comes to life, running circles around me, shaking his head and getting into everything. He will do his own version of binkies, not really leaping into the air very much, but he twists his head and body as he is running along, and sometimes will dart off here and there at Raphael-warp-speed. He does this for maybe half an hour, then I feed him and the other animals and he settles in to eat his dinner. Afterwards he will hop around for a bit (and decorate the kitchen with his own flair of bunny-ball decor), but for the most part he simply finds a favorite place in the kitchen and just lazes about. During the day when he is in his crate he sleeps, and the odd time that he does get bored he expresses it by tossing his dishes about or knocking the hay rack from the side of the cage. So I suspect that boredom for rabbits generally equates to pacing, tossing things about, digging, attempting to open their cage, etc.; while true depression is shown more as lack of enthusiasm, listlessness, non-response to attention, and/or not eating. Well, that's my observations, anyway....