Pet ownership has been linked to better mental health and enhanced well-being in the general population as well as in patients with physical and mental disorders (for a review see Wells [1]). For instance, pet ownership has been shown to be associated with lower levels of loneliness and depression and better perceived general health in older populations [2]. However, at the same time, some studies also find null or even negative effects of pet ownership on physical and mental health, raising the question whether pet ownership is robustly associated with better health (for a critical review see Herzog [3]).
To account for these diverging findings, it has been proposed that emotional attachment to pets moderates the relationship between pet ownership and mental health [4], with (mental) health-benefitting effects of pet ownership only be present in those pet owners who show a strong emotional attachment to their pets. Research suggests that humans are often strongly attached to their pets [5, 6] and sometimes report even stronger attachment to pets than to human family members [7]. Thus, recent research increasingly focused on the relationship between emotional attachment to pets and mental health. However, the current evidence does not confirm the hypothesis that a strong emotional attachment to pets is associated with better mental health. While some studies found a positive relationship between strong emotional attachment to pets and mental health [8,9,10,11], others did not find such an association [12,13,14,15], and the majority of studies even found a negative relationship between emotional attachment to pets and mental health [6, 16,17,18,19,20], that is, a stronger emotional attachment to one’s pet was linked to worse mental health. This effect is somewhat surprising and strongly contradicts the notion that only those pet owners who show a strong emotional attachment to pets experience (mental) health-benefitting effects of pet ownership. At the same time, the negative relationship between emotional attachment to pets and mental health raises the question what may account for this - at the first sight - paradox link.
An emerging line of research linking emotional attachment to pets to human interpersonal relationship and bonding experiences may provide first insights, with one study finding a stronger emotional attachment to pets being associated with (mostly interpersonal) childhood trauma and elevated levels of dissociation [21,22,23]. Other studies assessing human social support and emotional attachment to pets find that pet owners that are highly attached to their pet report lower levels of human social support [13, 24]. Furthermore, studies assessing attachment to pets, human social support mental health in the same sample found that pet owners with low levels of social support and a strong emotional attachment to pets report higher scores of loneliness and depression ([20, 25, 26]; but see [27]).
Interestingly, a person’s attachment to other humans is also related to well-being and mental health with insecure attachment styles being associated with poorer mental health (for a review see Dozier et al. [28]). Attachment theory was first proposed by Bowlby [29] to explain how infants form attachment to their primary caregivers. Ainsworth et al. [30] refined attachment theory by identifying four distinct attachment styles: (1) secure, (2) anxious, (3) avoidant, and (4) disorganized with the latter three representing insecure attachment styles. Children typically develop secure attachment styles when their primary caregiver is attentive and responsive to the children’s distress. Children with inconsistent or slow-to-respond caregivers typically develop anxious attachment styles. Avoidant attachment results from caregivers who consistently reject the infant, and disorganized attachment is believed to be an outcome of abuse and trauma [31,32,33]. Bowlby [33] assumed that the attachment a child forms with his or her primary caregiver early in life creates internal working models for close relationships in later life. Indeed, research shows that attachment style is relatively stable across the life span [34].
So far, little is known on the relationship between emotional attachment to pets and human attachment styles. Beck and Madresh [7] observed that emotional attachment to pets is generally rated as more secure than attachment to significant others. Taggart [35] found that people with a fearful attachment style report a stronger emotional attachment to their pets as compared to people with a secure attachment style. Furthermore, Beetz, Julius et al. [36] showed that children with an insecure-avoidant or disorganized attachment style profit more from the presence of a therapy-dog than from the presence of a friendly human under social stress.
When reviewing the findings on the association between attachment to other humans and emotional attachment to pets it has to be taken into account that while research into human attachment either assigns individuals to categories of attachment style or measures the strength of various categories of attachment (e.g., anxious or avoidant attachment) [37], most research into emotional attachment to pets comprises a unidimensional strength-based approaches ranging from weak to strong attachment. Recently, some studies have also employed categorical approaches (i.e., assessing attachment styles) to assess attachment to pets [38]. The present state of research does not allow for a conclusion which approach is better suited for research into emotional attachment to pets, however, the strength-based approach has been used more often resulting in a larger number of well-established psychometrically valid assessments [39,40,41,42].
It is yet not clear what links attachment to humans and emotional attachment to one’s pet. One pathway may lie in the use of a close emotional bond to pets as a compensatory attachment strategy for people who were not able to establish secure relationships to other people during childhood. Indirect support for this hypothesis may come from studies linking childhood trauma and childhood neglect to a stronger emotional attachment to pets [21,22,23] and from research showing that pet owners with low levels of social support and a strong emotional attachment to pets report higher scores of loneliness and depression ([20, 25, 26]; but see [27]).
However, to the best of our knowledge, so far there is only one dissertation project [12] that measured emotional attachment to pets and human attachment styles, as well as their levels of anxiety and depression in a sample of 300 dog, cat and horse owners. The dissertation found insecure attachment to humans to be associated with anxiety and depression. In contrast to previous findings, attachment to pets was not significantly correlated with insecure attachment to humans (anxiety and avoidance dimensions), depression, or anxiety. However, the findings should be interpreted with caution, as the study has not been peer-reviewed and assessed a relatively small and heterogenous sample including horse owners.
Given the strong bivariate relationships between emotional attachment to pets, attachment to humans and mental health, it is of great interest to assess all three measures in a relatively homogeneous sample of dog owners. The relationship between insecure attachment to humans and poor mental health has been very consistently shown. The association between attachment to pets and poor mental health has been less extensively researched, however, the majority of studies suggests that a stronger emotional attachment to pets is linked to worse mental health [6, 16,17,18,19,20]. Building on evidence that provided support for more insecure and anxious attachment to humans being related to a stronger emotional attachment to pets, we assumed that the relationship between emotional attachment to pets and mental health might be accounted for their shared variance with attachment to humans.
Thus, the present cross-sectional survey examined attachment to both pets and humans, mental health, and several pet specific variables in a sample of 610 German dog owners. We hypothesized that (i) a stronger emotional attachment to one’s dog is associated with higher mental health burden, and (ii) a stronger emotional attachment to one’s dog shows a negative association with indicators of secure human attachment and a positive association with indicators of insecure human attachment. Moreover, to disentangle the link between emotional attachment to pets and mental health burden and the association between emotional attachment to pets and human attachment and their respective associations with mental health burden, we used a mediation model comprising a link to mental health via (dimensional) human attachment (indirect paths) and direct path from emotional attachment to pets to mental health. We assume that only the indirect paths account for the link between emotional attachment to pets and mental health burden and thus, insecure human attachment is the key to explain higher mental health burden related to stronger emotional attachment to pets.