Beneficial Effects of Pet Ownership on Some Aspects of Human Health and Behaviour (Journal of the Royal Society of Medicine)
This study that I have selected is based on how animals can effect humans; whether it be about health, behavior, or both. The researchers wanted to be able to determine if owning an animal would be more beneficial than not owning an animal. Evidence for this subject is currently inconclusive, showing that there is still much to figure out about the possible benefits of owning a pet. Leading up to this study, there has been a few other studies demonstrating “transient decreases in blood pressure and/or heart rate in experimental human subjects in the presence of pet animals, but so far none has provided evidence of sustained improvements in any psychological measure as the result of pet ownership” (Serpell, 1991). This means that other studies have shown positive effects on blood pressure and/or heart rate but have not shown continued improvement on mental health (only upon initial pet ownership). There have also been other studies trying to detect any association between owning a pet and not owning a pet; some of which haven’t been replicated to gain more evidence to prove or disprove their hypothesis, some that have not detected an association, and some that have found positive results towards the association of owning a pet. The evidence above shows that this particular study still has a lot to be figured out and discovered.
James Serpell’s study was created to determine the changes in health status and behavior upon acquiring a new animal, either a dog or a cat. The study was based on a ten-month time period with two groups, pet owners and non-pet owners. There were a total of seventy-one pet owners with twenty-four cat owners and forty-seven dog owners, and twenty-six non-pet owners used as a comparison for the time period. There were only a couple of rules to participate in the study; anyone who had owned a cat or a dog in the previous year were excluded and only one person (the one who was going to have the greatest involvement with the animal) in the house was allowed to participate. Once the participants were selected they were interviewed at home and were asked to fill out self-report questionnaires that were to be returned within a 1-2 days of getting their new pet. Upon agreeing to participate in this study, the participants were told that this study was to “explore the ways in which pets affect their owners” (Serpell, 1991). This statement was said in a particular way to ensure that there was no positive or negative bias towards the end result. Within the self-report questionnaires, the participants were asked to fill out three separate measures of “physical and psychological health: (1) a checklist of 20
minor health complaints experienced by subjects by subjects during the previous month (Table 1, above) (2) a measure of the number and approximate duration of recreational walks taken by subjects during the previous 2 weeks (Table 2, above) and (3) the 30-item General Health Questionnaire (GHQ-30) – a measure of psychological components of ill-health” (Serpell, 1991). These questionnaires were all similar in structure and completed by the participants in the beginning of the study, at the end of the first month, at the end of six months, and at the end of the ten-month time period. The GHQ-30 was excluded at the first month of the study. The researchers used Statview 512+ and SPSSx which are statistical packages to help calculate the results. The journal states that the data on health and walking were skewed (right), which shows asymmetry in a graph that results are put into. The majority of the results could be on the right side of the graph showing a negative sew or the results could be on the left side of the graph showing a positive skew. Significance levels are normally based on 2-tailed tests which tests whether a sample is less than or greater than a certain range of values. If these values happen to fall in either one of these areas the alternative hypothesis would be accepted (the hypothesis originally stated in the beginning of any experiment) and the null hypothesis (the off chance that what is being tested does not have any effect) would be rejected.
The results are paired with P-values that help to determine which hypothesis (alternate or null) should be supported and which one should be rejected. These values range from 0 to 1; smaller values tend to support the alternate hypothesis (Ha) and larger values tend to support the null hypothesis (Ho). P-values of less than 0.01 show very strong evidence towards Ha, between 0.01 and 0.05 show strong evidence for Ha, between 0.05 and 0.10 show some evidence for Ha, between 0.1 and 1 shows no statistically significant evidence for Ha meaning supporting Ho. The results section is split into three groups to help keep the section organized: baseline comparisons, changes within groups, and differences between groups. Baseline comparisons: on average non-owners had fewer children (P=0.05), the non-owners belonged to higher socioeconomic groups (P=0.04), on average the dogs took more/longer recreational walks (P=0.02). The paper stated that “the three groups did not differ significantly from each other in terms of age, marital status, sex-ratio, type of housing, number of minor health problems reported, or GHQ-30 scores” (Serpell, 1991). The sample interquartile ranges and medians for the three variables (GHQ-30 scores, number/duration of recreational walks, health problems) are listed in Table 3 (left). Changes within groups:
non-owning group did not change significantly in health problems or GHQ-3o scores but increased the amount of recreational walks (P=0.04, results may have been due to a season change), dog-owners reported a highly significant decrease in health problems (P<0.0001, for the first month and persisted to the 6 month mark and at the 10 month mark the p-value changed to 0.02(not as significant at the end of the study)), dog-owners also exhibited a decrease in their GHQ-30 scores which meant that they had improved throughout the study (P=0.0006 at 6 months and P=0.01 at 10 months), dog-owners exhibited a large increase in the number and duration of recreational walks throughout the study (P<0.0001), cat-owners reported a significant reduction in health problems (P=0.001, this was no longer significant after the 6 month mark), cat-owners also showed a minor improvement in their GHQ-30 scores during the first 6 months (P=0.04, result was obtained using a one-tailed estimate), cat-owners showed no change in number/duration of recreational walks. The journal states that there was no association found between self-reported improvements in health and recreational walking, but there was an association found between an increase in the number/duration of recreation walks and improvements in the GHQ-30 scores between baseline and the 6-month mark (P=0.003; meaning it wasn’t statistically significant at 10 months). Differences between groups: non-owners showed significantly smaller changes in health than cat-owners (P=0.012) or dog-owners (P=0.013); these were compared from baseline to one month, baseline to 6 months, and baseline to 10 months and all were similar results. Other than these results, no other differences between the groups were found statistically significant.
The results section is only used for reporting what is found throughout the study. The next section in this is the discussion section, this is where the results are assessed and interpreted. We find out the significance of our findings and can suggest why certain things happened throughout the study. In the beginning of this section, it was stated that “the effects of pet acquisition on human health and behavior cannot be investigated using conventional double-blind, placebo-controlled trials. Also, people voluntarily acquiring pets from animal shelters, and agreeing to participate in research, are not a randomly selected sample” (Serpell, 1991). This means that this particular study was not arranged in a normal experiment setting: a double-blind study means that neither the participant or the experimenter knows who is getting the treatment, a placebo is normally used as a control in the experiment, normally participants are randomly selected and in large amounts to ensure that there is no bias towards the results and that there is a chance for everyone to be selected for the experiment. The changes about health that were reported were considered to be general rather than specific and were not attributed to chance improvements in seasonal ailments. Some of these results could have resulted in part by the novelty of animal companionship in the beginning of the study, but does not explain how the health effects lasted until 10 months. The results from the increased physical exercise helped to distinguish the dog-owners from the other two groups. These results also showed that there could be positive lasting health implications. Pet ownership is currently not considered to be significant in public health, but these results showed a lot of health benefits by owning an animal. This could be the start of a new experiment to explore the areas and mechanisms of this particular benefit.