Lmao yes they exist. Their genetic code is slightly different from ours (at least other mammals, obviously our genetic code and a fish’s genetic code are way different from each other), but animals have their own version of Down syndrome, retardation, social anxiety, PTSD, etc. Yes. Animals can be born or develop mental disabilities too. Not to mention when they get old, like dogs for example, they also can develop dementia and things that humans run the risk of developing as they get older.