Cats and dogs are observant and intuitive, and they may seek physical contact if they sense depression or sadness in their human companions. But even if the animals are unaware of it, cats and dogs can ease human depression simply by being there.
Petting an animal or having an animal nearby can cause the human brain to release endorphins and other chemicals that counteract pain and cause a sense of pleasure or well-being. Cats and dogs are the best pets for depression, but many animals, including birds, guinea pigs, hamsters, rabbits, and horses, can also help support good human mental health.