I am no expert and have no knowledge of the ratio of which ppl are more attached to animals. I do believe mental disorders can play a roll in which we feel the need to attach to our pets but some don't. I don't believe it is a bipolar thing but for some of us it can be therapeutic. Our house is a small zoo . . . lol. My husband has his dogs and I have my reptiles which I am addicted to. I also have a bleeding heart for the suffering ones and if I had the means I would be a rescue. So for you, maybe bipolar plays something in it, but I think being an animal lover is seeded in your soul.