They're often referred to as one of the family - so if a pet is unwell, it’s not just the animal that will feel it.
Having a sick pet can make its owners more likely to suffer depression and anxiety and have a poorer quality of life, a study has found.
Pet ownership has previously been found to have benefits in terms of relieving stress and getting more exercise, in the case of dogs. But when a family dog or cat is unwell, it can have a huge psychological impact on its owners, researchers discovered.
In humans, the problem is well known as the "caregiver burden" - the impact of sickness on family members or friends who care for the sufferer. But in pets, the issue has not received the same scientific attention.
Now US researchers at Kent State University in Ohio have compared 119 owners of sick dogs or cats with the same number whose pets were healthy.
Levels of stress, anxiety and depression were assessed along with quality of life. Owners of animals with chronic or terminal disease suffered most, they found.
The authors of the study, published in the Veterinary Record, explain that their findings "may help veterinarians understand and more effectively handle client distress in the context of managing the challenges of sick companion animal caregiving".
But they suggest that research is needed to better understand risks for caregiver burden in the client, how this might be reduced, and how it might affect the wellbeing of the vet as well.
Last year, the British singer Joss Stone cancelled tour dates in the Caribbean because her Rottweiler Missy was ill. She said at the time: "Missy is the closest thing I have to a child.
"I know to some that may sound ridiculous, but for me it is everything. I have to go back and make sure she is okay before I can continue with the tour."
Stone added: "I hope that those who had planned to attend the shows can understand. I will come back, I promise, but right now Missy comes first. "Please say a prayer for Missy.
“I don’t know what I will do if she is not around."
- Daily Mail