The levels of stress in dogs and their owners follow each other, according to a new study from Linköping University, Sweden.
The scientists believe that dogs mirror their owner’s stress level, rather than vice versa. The study has been published in the scientific journal Scientific Reports.
Researchers at Linköping University have examined how stress levels in dogs are influenced by lifestyle factors and by the people that the dogs live with.
Previous work has shown that individuals of the same species can mirror each others’ emotional states.
There is, for example, a correlation between long-term stress in children and in their mothers.
The recently published study arose from scientists speculating whether similar mirroring of stress levels over long time periods can also arise between species, such as between the domesticated dog and humans.
The researchers determined stress levels over several months by measuring the concentration of a stress hormone, cortisol, in a few centimetres of hair from the dog and from its owner.
“We found that the levels of long-term cortisol in the dog and its owner were synchronised, such that owners with high cortisol levels have dogs with high cortisol levels, while owners with low cortisol levels have dogs with low levels”, says Ann-Sofie Sundman of the Department of Physics, Chemistry and Biology (IFM) at LiU, principal author of the study and newly promoted doctor of ethology.
The study examined 25 border collies and 33 Shetland sheepdogs, all of them owned by women.
The owners and the dogs provided hair samples on two occasions separated by a few months.
Since physical activity can increase cortisol levels, the researcher also wanted to compare companion dogs with dogs that competed in obedience or agility.
The physical activity levels of the dogs were therefore recorded for a week using an activity collar.
Previous research has shown that levels of short-term cortisol in saliva rise in a synchronous manner in both the dog and its owner when they compete together.
The study presented here, in contrast, found that physical activity in dogs does not affect the long-term cortisol in their hair.
On the other hand, the stress level of competing dogs seems to be linked more strongly with that of the owner.
The scientists speculate that this may be associated with a higher degree of active interaction between the owner and the dog when they train and compete together.
The dog owners were also asked to complete two validated questionnaires related to their own and their dog’s personality.
The researchers investigated whether stress levels are correlated with personality traits.
“Surprisingly enough, we found no major effect of the dog’s personality on long-term stress.
The personality of the owner, on the other hand, had a strong effect.
This has led us to suggest that the dog mirrors its owner’s stress”, says senior lecturer Lina Roth, also at IFM, and principal investigator for the study.
The result suggests that the match between an owner and a dog affects the dog’s stress level.
Further studies are, however, needed before we can draw any conclusions about the cause of the correlation.
The researchers are now planning to study other breeds.
Both the border collie and the Shetland sheepdog are herding dogs, which have been bred to collaborate well with humans and respond accurately and quickly to signals.
The research group is planning to investigate whether a similar synchronisation takes place between dogs and humans in, for example, hunting dogs, which have been trained to be independent.
Another line of research will look at whether the sex of the owner plays a role.
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Previous research has shown that levels of short-term cortisol in saliva rise in a synchronous manner in both the dog and its owner when they compete together.
The image is in the public domain.
“If we learn more about how different types of dog are influenced by humans, it will be possible to match dog and owner in a way that is better for both, from a stress-management point of view.
It may be that certain breeds are not so deeply affected if their owner has a high stress level”, says Lina Roth.
Funding: The study has received financial support from Agria, the SKK (Swedish Kennel Club) Research Fund, and the European Research Council (ERC).
Pet dogs have a notable impact on the lives of children. More than 40 percent of American families with children have a pet dog (American Pet Products Association, 2014).
Pet dogs have been proposed to benefit children by reducing anxiety and facilitating social interactions (e.g., Hoffmann et al., 2009; Kruger & Serpell, 2006).
However, the research literature on potential benefits of child-dog interaction is scant.
Dogs have been shown to promote positive affect and reduce problem behavior among typically developing and developmentally disordered children (e.g., Anderson & Olson, 2006; Kotrschal & Ortbauer, 2003).
Other potential socio-emotional benefits of pet dogs for children include increased autonomy, self-concept, and empathy (Barker & Wolen, 2008).
However, the bulk of this research has been descriptive, and relatively few experimental studies have been conducted to rigorously test commonly held beliefs about the benefits of pet ownership for children.
Moreover, the mechanisms by which pet dogs may confer emotional health benefits for children are still unclear.
One potential mechanism may be via social buffering of stress responses.
During childhood, emotional and physiological responses to stress are still developing (Eisenberg, Spinrad, & Eggum, 2010), and children possess less mature internal cognitive resources to self-regulate stress responses compared to adults (Cole, Michel, & Teti, 1994).
As such, social regulation of stress responses provided by supportive figures, such as family members, is essential for children’s adaptive socio-emotional developmental outcomes (Gunnar & Donzella, 2002).
The social buffering hypothesis has gained increasing traction over the past several decades as a means by which supportive social relationships may reduce responses to stressful or threatening events (Cohen & Wills, 1985; Hennessy, Kaiser, & Sachser, 2009; Hostinar, Sullivan, & Gunnar, 2014).
In the developmental literature, social buffering has primarily focused on infancy and early childhood, with little research conducted in middle childhood (Hostinar et al., 2014).
We focused on typically developing children aged 7–12, based on social and emotional developmental changes in middle childhood.
First, children of this age can reliably self-report feelings of stress (Achenbach, McConaughy, & Howell, 1987), owing partly to the development of metacognitive abilities (Grazzani & Ornaghi, 2012). Second, social stressors reliably elicit a cortisol response in this age group (Gunnar, Talge, & Herrera, 2009).
Extensive research has shown that social evaluation is one of the most reliable elicitors of the cortisol stress response (Dickerson & Kemeny, 2004).
Seven- to twelve-year old children, compared to younger children, more regularly engage in self-reflective perspective taking, viewing their behavior from another’s point of view (Cillessen & Bellmore, 1999; Selman, 1976).
As a result, during middle childhood, self-concept more frequently involves social comparisons and is influenced by feedback from others (Cole et al., 2001; Harter, 1998).
A consequence of these developmental changes relevant to stress research is that social evaluation becomes a salient stressor beginning in middle childhood.
Third, by middle childhood the amount of time children spend with parents declines dramatically compared to earlier ages (Lam, McHale, & Crouter, 2012).
Simultaneously, parents typically engage in coregulation with children, exercising general oversight while shifting control of moment-to-moment decisions to children.
Correspondingly, children start to utilize less parental support for stress coping (Kerns, Tomich, & Kim, 2006). Parental support is partially replaced by reliance on a broader network of social support figures compared to infancy and early childhood including pets (Bryant, 1985).
This developmental change necessitates studies on social buffering resources other than parental figures for older children.
This research is essential as there is solid evidence that the social environment during development has permanent, programming effects on the stress response system (Lupien, McEwen, Gunnar, & Heim, 2009).
In addition, emotional and physiological responses to stress during childhood are known risk factors for internalizing and externalizing problems in childhood, as well as stress-related disorders in adulthood (Ingram & Price, 2010).
An examination of stress buffering during childhood, therefore, is important to further the understanding of developmental trajectories of risk and resilience for stress-linked emotional, behavioral, and physical health problems.
The few studies examining stress buffering effects of child–dog interaction have mostly been conducted in medical settings (Beetz, Uvnäs-Moberg, Julius, & Kotrschal, 2012; Hansen, Messinger, Baun, & Megel, 1999; Havener et al., 2001; Nagengast, Baun, Megel, & Leibowitz, 1997).
These studies show inconsistent results, as some documented significant stress-reducing benefits of pet dogs (e.g., Nagengast et al., 1997), but others did not (e.g., Havener et al., 2001).
These discrepancies are likely due in part to diverse, uncontrolled effects of a variety of medical procedures and hospital stays on emotional or physiological stress.
Human-animal interaction (HAI) research with adults has provided some support for the idea that interaction with dogs has stress-reducing benefits (Barker & Wolen, 2008).
Adults undergoing a laboratory stress task in the presence of a pet dog show reduced physiological response (heart rate, blood pressure, skin conductance) compared to adults undergoing the same task alone; in contrast, adults undergoing the task in the presence of a human friend showed elevated autonomic stress response compared to those performing the task alone (Allen, Blascovich, Tomaka, & Kelsey, 1991).
Allen et al. (1991) have suggested that pet dogs provide non-evaluative companionship to owners that reduce stress responses compared to more evaluative human companions.
The bulk of the research on stress-buffering effects of HAI has focused on the autonomic component of the biological stress system, as indexed by heart rate, blood pressure, or skin conductance.
Although autonomic activity plays a key role in mobilizing the body’s fast-acting response to threat, the emotional component of stress and the cortisol response to stress are arguably more relevant for long-term developmental consequences.
Emotional and cortisol stress responses impact neural activity in developing prefrontal and limbic brain regions that control stress-related memory, emotion, and enduring changes in stress responsivity (McEwen, 2008).
Moreover, perceived stress during childhood has been linked with emotional and behavioral problems as well as maladaptive coping styles (e.g., Dieleman, van der Ende, Verhulst, & Huizink, 2010; Hampel & Petermann, 2006).
A proportional and time-limited cortisol response to stress can be adaptive in the face of an immediate danger or threat. However, disproportionate, frequent, or prolonged activation has been linked with multiple forms of psychopathology and related alterations in amygdalar and hypothalamic functioning (e.g., Dieleman et al., 2010; Vaisvaser et al., 2013).
Perceived stress and cortisol responses to stress are largely orthogonal dimensions of stress responding (Campbell & Ehlert, 2012).
Whereas perceived stress reflects processes that are consciously accessed, cortisol responses to stress are not part of conscious awareness but also shape emotional and physiological responses to future stressors.
Two studies with adults have examined both perceived stress (self-reported anxiety) and cortisol response to stress in the presence or absence of an unfamiliar friendly dog. However, these two studies yielded contradictory findings, with one study reporting a buffering effect of the unfamiliar dog’s presence for state anxiety but not cortisol, and the other showing the reverse pattern (Lass-Hennemann, Peyk, Streb, Holz, & Michael, 2014; Polheber & Matchock, 2014).
There is only one published study reporting lower cortisol during the recovery phase of a stress protocol. However, that study compared the effects of an unfamiliar live dog to a toy dog and was conducted with boys recruited primarily from special education schools (Beetz, Julius, Turner, & Kotrschal, 2012).
To date, the question of whether dogs buffer children’s cortisol responses has not been tested in an unselected sample.
There are no studies empirically testing whether dogs buffer children’s perceived stress responses.
Among adults, social support figures buffer perceived stress via provision of emotional/companionship support as well as informational and instrumental support (Lakey & Cohen 2000). Children and adolescents report emotional/companionship support as more effective in reducing emotional distress compared to informational/instrumental support (e.g., Caserta, Punamäki, & Pirttilä-Backman, in press).
Whereas guide, therapy, or rescue animals are trained to provide instrumental support, among typically developing children, pet dogs’ support is generally emotional/companionship in nature.
With developmental changes in middle childhood leading to improved ability to engage in self-reflective thought (Achenbach et al., 1987), increased attention to self-evaluation (Cole et al., 2001; Harter, 1998), decreasing reliance on parents for stress coping (Kerns et al., 2006), and increased reliance on pets for emotional support (Bryant, 1985) it is plausible that dogs’ companionship during a stressor may buffer children’s perceived stress.
Additional limitations of prior research are that most studies (in both adults and children) have utilized unfamiliar animals and participants comprised of both pet-and non-pet owners (e.g., Allen, Blascovich, & Mendes, 2002; Demello, 1999; Kingwell, Lomdahl, & Anderson, 2001).
The use of unfamiliar animals as well as participants varying in pet ownership has likely contributed to the mixed findings in the literature. Indeed, research with adults has shown that presence of a dog lowers heart rate and blood pressure only among pet owners (Allen et al., 2002; Kingwell et al., 2001).
Among non-owners, heart rate is higher in the presence of a dog (Kingwell et al., 2001). Dog owners may reap greater benefits from interaction with dogs based on their history of pet ownership.
Moreover, a potential stress-buffering effect may be maximal in the presence of one’s own pet dog, as both children and adults report strong feelings of emotional attachment toward their pet dogs (Daly & Morton, 2006; Kurdek, 2008; Serpell, 1996).
The present study advances research on the potential stress-buffering effect of HAI in childhood by examining perceived stress and cortisol responses to stress among pet-owning children in a controlled laboratory experiment.
Based on evidence that pet ownership impacts whether dogs can confer a stress-buffering effect (Allen et al., 2002; Kingwell et al., 2001), and that children form strong social bonds to pet dogs (Westgarth et al., 2013), we tested whether pet dogs would buffer stress responses among children. In contrast to most prior studies utilizing unfamiliar dogs (e.g., Beetz, Julius, et al., 2012; Friedmann, Katcher, Thomas, Lynch, & Messent, 1983), this study was conducted with children and their own pet dogs.
To rigorously test the potential stress-buffering effect of pet dogs, we utilized a well-established laboratory-based paradigm, the Trier Social Stress Test for Children (TSST-C, Buske-Kirschbaum et al., 1997). Based on prior research using the TSST, we anticipated that results for perceived stress and cortisol stress responses may diverge (see for review Campbell & Ehlert, 2012).
Nevertheless, as a direct test of the potential buffering effect of pet dogs we hypothesized that children experiencing the TSST-C in the presence of their pet dog would show lower perceived stress and cortisol response to stress in comparison to children experiencing the TSST-C without their pet dog present.
As a robust test of the stress-buffering effect of pet dogs specifically, we also compared the stress-buffering effect of pet dog presence against a second group in which social support was provided by presence of a parent during the TSST-C.
A secondary aim specifically targeted the subset of children experiencing the stressor in the presence of their pet. Research has documented that forms of interaction between a child and pet dog can vary widely (Millot & Filiatre, 1986; Millot, Filiatre, Gagnon, Eckerlin, & Montagner, 1988).
Anticipating that pet dog behavior and child-pet relationships would naturally show some variation even in an experimental paradigm such as the TSST-C, a secondary aim of this study was to test whether individual differences in child-dog interaction impacted the stress-buffering effect of pet dogs.
Prior research suggests that dogs show differences in a variety of personality dimensions such as ‘aggression’, ‘playfulness’, and ‘sociability’ (Svartberg, Tapper, Temrin, Radesäter, & Thorman, 2005).
Recent research in our lab has demonstrated that children report more positive emotional feelings toward pet dogs if the dogs are responsive to their communicative gestures (Hall, Liu, Kertes, & Wynne, 2016).
Presumably, child-dog dyadic interaction during the TSST-C may impact the social buffering effect the dog may provide. However, no prior studies examining the stress-buffering effect of dog presence have assessed dog behaviors during the study and whether variation in these behaviors is related to stress responses.
Prior research with adults demonstrates that petting and social interaction induces physiological changes in humans, including reductions in cortisol along with increases in β-endorphins, prolactin, β-phenylethylamine, oxytocin, and dopamine (Miller et al., 2009; Nagasawa et al., 2015; Odendaal & Meintjes, 2003). However, impacts of human–dog interaction with phenotypes similar to perceived stress (i.e., state anxiety) have been reported less consistently (Lass-Hennemann et al., 2014; Polheber & Matchock, 2014).
The present study assessed child–dog interaction via behavioral coding of the child-dog dyad during the TSST-C.
We hypothesized that for children in the pet present condition, lower perceived or cortisol stress response would be observed for dyads in which dogs sought out and remained near the child (dog initiated interactions) or dyads in which children actively engaged the dog (child initiated interactions).
Source:
Linkoping University
Media Contacts:
Karin Söderlund Leifler – Linkoping University
Image Source:
The image is in the public domain.
Original Research: Open access
“Long-term stress levels are synchronized in dogs and their owners”. Ann-Sofie Sundman, Enya Van Poucke, Ann-Charlotte Svensson Holm, Åshild Faresjö, Elvar Theodorsson, Per Jensen & Lina S. V. Roth.
Scientific Reports. doi:10.1038/s41598-019-43851-x
