Sounds cool, Seth! I disagree with Maxle pretty strongly, because cute fluffy animals are cute and fluffy. Anthropomorphising them might take away from that for some people depending on how it was done, though. If it was just an ordinary cat and an ordinary dog, at least I feel like that'd make more sense and might be more motivational, assuming that's a part of the story's value; almost anyone can find themselves a pet cat or a dog, which really
can help a lot when it comes to overcoming depression. I mean, my pet cat Jamppa was really one of the few things that gave me any kind of happiness at all when I was depressed, just being all cuddly, jumping all over the place and meowing in my face when I woke up. He couldn't talk or anything, obviously, but in their own way, pets
do talk to their owners (I don't really like that word, but meh) by various unique forms of interaction like the way their tail moves around, what type of sounds they make, etc.
But I totally understand the appeal in making the animals talk in the story. Talking animals are cool, and can even add a feeling of significant symbolism where none exists, if done well. Besides, most readers would probably interpret them as some representation of the protagonist's inner feelings, so it wouldn't matter what they actually were, and thus it'd make perfect sense for them to be "normal" animals that just talk.
I've considered writing a short story about talking crows solving a murder just for the sake of the puns, but haven't gotten around to it.
I probably misunderstood one thing in your description, though; do you mean that the dog and the cat would be lovers? Or the man and the cat? Because... well, honestly, that's a whole another level of creepy. I'd assume that most readers would already have trouble relating to the guy by the time you bring up his depression, but when it'd become an issue that he has a
thing for cats... well... let's just say that interspecies romances have their time and place, which I personally feel like is in comedy and horror, when it's used to deprave a character or two to the next level. Well, with the occasional exception of humanoid aliens and such that don't fall into the uncanny valley, as those can sometimes be done in a serious context without coming across as disturbing and/or hilarious.
No offence if you're part of the furry fandom, sexually or not; I don't have anything against that (why would anyone?), but I do have lots of things against people who do things to non-human animals.
I'm not saying you should change that (assuming I understood correctly), but I mean, most readers would probably not take the story very seriously after that, if they even kept reading. I don't know about myself, I'd probably keep reading and be all like "what the f**k is this s**t, the man's saving the cat's life to
DO WHAT!?". You could obviously prove me wrong and pull it off perfectly, though, haha.
Anyway, since you said you don't mind suggestions:
If it's all a waking hallucination, you could easily milk in lots of depth and symbolism by interplaying with his hallucinosis and the world as it is, maybe brief lucid periods with thematic triggers that then lead back into the warped state of things. Depending on how in depth you're planning to go with it and what kind of an atmosphere you'd want, there could even be a cycle of emotional states that'd be reflected into his world in various seemingly physical ways.
But like, he couldn't really be
just depressed if his hallucinations lasted for weeks, months, or whatever, unless his supply of the chemicals was somehow magically replenished.
He'd have to be also psychotic, for example; but that's kinda reasonable and wouldn't detract from his depression being at the centre if that's your plan, since those chemicals could've caused/triggered that to begin with.
If he was in a coma, I suppose that'd give you a lot more creative freedom and whatnot as it wouldn't have to stick to the laws of physics or, well, make any sense at all, but that might take away the "this is a story about a man overcoming depression"-thing and turn it into a "this is a story about a man with some messed up thoughts"-thing.
As for the "chaotic, with no obvious explications"-part, I myself consider that a bit pointless. I mean, if it's literally chaos without any psychological basis, then the protagonist would have to be pretty damn blown out of his mind and it could well end up being "surreal, but not surrealist" if that makes sense. Of course, I'm not saying that that's a bad thing, just that it wouldn't make much sense for it to come out that way if it was all in the protagonist's head because he came in contact with some hallucinogenic stuff, as far as I know.
Then again, I've never used any psychedelic drugs, so I could be wrong. Maybe the hallucinations can have all types of external sources, but from what I've understood, they're generally a lot like dreams in that they're based on your subconsciousness and real world stimuli that are processed differently in the brain, etc. or something like that... although I did just read about a plant (angel's trumpet) that apparently can cause hallucinations that are entirely unrelated to anything, so it's probably possible for some chemicals to cause that same reaction.
PS: I've been writing as well, a kinda surreal horror thing about an elderly gardener. Hopefully, I can finish it soon.