Pet ownership: good for health?

CURRENT ISSUE of the Journal (page 466), Parslow and Jorm 1 reopen the debate about whether pets benefit human health.They give the results of a high quality Australian sample survey indicating that pet owners do not have lower blood pressure than non-owners, and, in this respect at least, are not at lower risk of heart disease.Their results run counter to an earlier Australian study, 2 based on a large volunteer sample, in which pet owners were found to have lower blood pressure and cholesterol levels.Where are we up to in this debate -are we back to square one?The case I will present here is that we can be fairly confident that pets do confer health benefits, but we do not know exactly how.Several types of research by very different kinds of scientists -medical scientists and social scientists -have been conducted on this topic.These scientists have different understandings of causation (ie, of what it means to claim that pets cause their owners to have better health), and, because of this, it is difficult to have a meeting of minds.However, it can be argued that social science research forms a natural prelude to medical research, and that the social science evidence in favour of health benefits of pet ownership makes it worthwhile to mount a substantial medical research effort to discover how the benefits occur.Social science surveys in Australia, 3 Britain, 4 Germany 5 and the United States 6 during the 1990s have come pretty close (in social science terms) to establishing that pets produce health benefits.The first surveys were crosssectional (ie, they provided snapshot evidence at one point in time).With some exceptions, they showed that pet ownership is associated with better self-reported physical and psychological health, and also fewer doctor visits.Controlling for the main demographic variables associated with health problems, including sex, age, marital status, education and income, did not change the results.Of course, social scientists recognised that causation might run the other way round, or even both ways.It was possible that people who were healthy and happy in the first place tended to acquire pets, rather than that having a pet caused better health.So, as a next step, efforts were made to design valid longitudinal studies (ie, studies following people over a period of time) to see whether owning a pet made a difference.The strongest positive evidence has come from the German Socio-Economic Panel Survey, 5 which asked a sample of about 10 000 respondents about pet ownership in 1996 and again in 2001.Controlling for health status in 1996 (as well as for the usual demographic variables), it was found that people who continuously owned a pet reported the fewest doctor visits (in the 3 months before interview), and those who had acquired a pet during the 5-year period reported the next fewest number of visits.Both these groups went to the doctor about 10% less often than people who did not have a pet at either time, or who had ceased to have