Pet owners have long been encouraged to think that they are happier, healthier and live longer than people without pets, but a new US study claims they might be barking up the wrong tree.Howard Herzog, a professor of psychology at Western Carolina University, says studies conducted in the past to determine whether having a pet improves health and longevity have \"produced a mishmash of conflicting results.\"\"While pets are undoubtedly good for some people, there is presently insufficient evidence to support the contention that pet owners are healthier or happier or that they live longer\" than people without pets, Herzog wrote in the August issue of Current Directions in Psychological Science.\"While some researchers have reported that positive effects accrue from interacting with animals, others have found that the health and happiness of pet owners is no better, and in some cases worse, than that of non-pet owners.\"Herzog cites several studies purportedly showing the benefits of having a pet, including one from 1980 which showed that heart attack victims who had a pet were around four times more likely than petless victims to survive for a year after the crisis, but said more gloomy studies had been ignored.\"While the media abounds with stories extolling the health benefits of pets, studies in which pet ownership has been found to have no impact or even negative effects on human physical or mental health rarely make headlines,\" he said.One study conducted last year found that pet owners were more likely than non-owners of pets to die or suffer another heart attack within a year of suffering a first crisis. That study got no media coverage, Herzog says.He cited another study which found no difference in blood pressure between older pet-owners and the petless. In fact, the pet owners in that study exercised less than the non-owners and were more likely to be overweight.Other large-scale studies conducted in the United States, Australia, Sweden and Finland also appeared to show few benefits to physical or psychological health from pet ownership, according to Herzog.The professor, a pet owner himself, stressed he was not condemning pet ownership or the use of therapy animals for children with autism or people with psychological disorders, but wanted to see more scientific research done.Until that research is completed, \"the existence of a pet effect on human health and happiness remains a hypothesis in need of confirmation rather than an established fact,\" he says.