Research Paper

Animals – the Emotional and Biological Effect on Humans: It’s more than just caring

March 13, 2018

Author: Elizabeth Fey – September 2017

Does interaction between humans and animals provide significant health benefits?  From the very early times, canines switched their allegiance from pack to man, domestic animals have served humans and, in some cases, formed emotional bonds with them.  In addition to their roles as companions and helpers, animals have also been thought to help the physically or mentally ill or disabled to cope or heal. Even before interest in health-promoting effects of human-animal interaction grew in the 1960s, animals had been used for therapeutic purpose.  “Being around dogs can have a calming effect,” pet writer Maryann Mott reported for National Geographic News years ago. “Studies have shown that physiological changes occur when people touch dogs: a drop in heart rate, lower blood pressure, and reduced stress.”  While relatively limited, there is also evidence that supports tertiary evidence of other physiological changes that occurs with the reduction of stress-related parameters such as epinephrine and norepinephrine; improvement of immune system functioning and pain management; increased trustworthiness of and trust toward other persons; reduced aggression; enhanced empathy and improved learning. The theory is that the activation of the oxytocin system plays a key role in the majority of these reported psychological and psychophysiological effects of human-animal interfaces.

What we know: 

There has been a steady growth trend relating to animal assistance in therapy, education and overall care and there has been numerous studies spread across several journals which appears to have a common underlying mechanism, the activation of oxytocinergic system and its role in social stress modulation.  This system can be linked directly to many of the observed physiological effects of human-animal interface and may also be indirectly associated with the other, psychological effects.

Literature Review:

There has been 69 original studies on the human-animal interface. Among the well-documented effects of human to animals of different ages, with and without special medical, or mental health conditions are benefits for: social attention, social behavior, interpersonal interactions, and mood; stress-related parameters such as cortisol, heart rate, and blood pressure; self-reported fear and anxiety; and mental and physical health, especially cardiovascular diseases. Limited evidence exists for positive effects of human-animal interface on: reduction of stress-related parameters such as epinephrine and norepinephrine; improvement of immune system functioning and pain management; increased trustworthiness of and trust toward other persons; reduced aggression; enhanced empathy and improved learning. Studies analyze the impact of the oxytocin system which plays a key role in the majority of these reported psychological and psychophysiological effects of human-animal interface.  Oxytocin and human-animal interface effects largely overlap, as documented by research in both, humans and animals, and first studies found that human-animal interface affects the oxytocin system. As a common underlying mechanism, the activation of the oxytocin system does not only provide an explanation, but also allows an integrative view of the different effects of human-animal interaction.


Studies focused on the facilitation of interpersonal interaction by the presence of an animal, the social catalyst effect. Among children with autism the presence of a dog during occupational therapy was associated with greater use of language and more social interaction (Sams et al., 2006).  In psychiatric inpatients, animal assisted therapy lead to a significant increase in interactions with other patients over the course of 4 weeks.  This included smiles, sociability, helpfulness toward others, activation and responsiveness (Marr et al., 2000).  There is also supporting research by Hergovich et al. (2002) documented a positive effect of the presence of dogs in the classroom on the development of empathy in children. When compared to a control class, the class with the dogs showed higher scores in field independence and empathy toward animals.  In their meta-analysis Souter and Miller (2007) conclude that animal-assisted interventions have the potential to significantly reduce depressive symptoms.  Human-animal interaction has also been investigated for its effects on hormonal indicators of stress such as cortisol, and on neurotransmitters such as epinephrine and norepinephrine.  Odendaal (2000) and Odendaal and Meintjes (2003) assessed changes in plasma cortisol in dog owners when petting their own, or an unfamiliar dog, or quietly reading a book. The interaction with their own dog, and also with the unfamiliar dog, but not the reading condition led to a significant decrease in the cortisol levels of the humans.  A substantial number of well-designed studies investigated the effect of human-animal interface on blood pressure and heart rate, some also included skin temperature or skin conductance, either in the absence of a specific stressor or during a stress-inducing task. A positive attitude toward companion animals was associated with lower mean arterial pressure and systolic blood pressure. Vormbrock and Grossberg (1988) assessed heart rate and blood pressure while undergraduates interacted with a dog visually, verbally, or tactually. Blood pressure was highest while talking to the experimenter and lowest during stroking the dog.  Several studies also investigated whether animal contact can reduce fear and anxiety elicited by a stressor. The elderly residents of a nursing home with a resident dog, reported less tension and confusion in comparison to residents of a home without a dog. Also Perkins et al. (2008) and Filan and Llewellyn-Jones (2006) concluded from their reviews that dog-assisted therapy reduces restlessness in elderly patients with dementia.  Evidence for the effects of human-animal interface on cardiovascular diseases was gained from the following studies: Headey (1999) found that dog and cat owners were less likely to take medication for heart problems than non-pet owners.  Charnetski et al. (2004) reported a significant increase in salivary immunoglobulin A (IgA), an indicator of good immune system functioning, in college students after stroking a live dog in comparison to stroking a stuffed dog or sitting quietly for 18 min.  The peptide hormone oxytocin (OT) is produced in the hypothalamus and released into the circulatory system and the brain in response to sensory stimulation via a network of OT-containing nerves (Landgraf and Neumann, 2004; Ross et al., 2009), e.g., during breastfeeding, labor, sex, but also touch, warmth, and stroking, usually in the context of trusting relationships (for reviews see Uvnäs-Moberg, 2003; Insel, 2010). Many physiological, psychological and behavioral functions are modulated via OT, as has been shown via experimental administration of OT in animals and humans.  Odendaal (2000); Odendaal and Meintjes (2003) documented a significant increase of plasma OT, as well as prolactin, phenylacetic acid, and dopamine, in both, humans and dogs after 5 to 24 min of stroking a dog.


Existing evidence clearly points at the potential of interactions with animals, especially one’s own pet-dog, to increase OT levels in humans.  Both, human-animal interaction and OT, were found to promote social interaction, to reduce stress and anxiety, and to enhance human health. OT is released via eye contact, but in particular, via pleasant tactile interactions which seem to play a major role for the OT-mediated decrease of stress levels.  Oxytocin effects may be triggered in response to single meetings with animals, but stable relationships with animals such as pet ownership will be linked to more potent and long lasting effects due to repeated exposure to OT.

List Reference/Bibliography: Available upon request