Awesome Animals: Human-Animal Interaction and Homeostatic Balance

            Many of us have heard about Animal-Assisted Therapy (AAT). In fact, Regis’s Active Minds brings in therapy dogs during finals weeks specifically to provide students with AAT. This is because animals have been shown to relieve stress in a variety of settings—they relieve stress in patients just prior to receiving ECT (Barker, 2003), and they relieve stress in survivors of sexual assault suffering from PTSD (Lefkowitz, Paharia, Prout, Debiak, & Bleiberg, 2005). In less extreme circumstances, and directly related to the Active Minds activity, Human-Animal Interaction (HAI) relieves stress in college freshman who are leaving home for the first time (Adamle and Riley, 2010), stress brought on by the mental stressor of mental math (Allen, Shykoff, & Izzo, 2001), and even state anxiety associated with the presence of a tarantula (Shiloh, Sorek, & Terkel, 2003). All of these studies were experimental, introducing animals to participants upon arrival to a lab study or monitoring participants after providing them with a pet dog or cat. And together, these studies found decreases in stress using both anxiety inventories and blood pressure.

            As implied above, animals decrease blood pressure. Not only do they decrease blood pressure, but they also significantly and positively impact human health. Along the same lines as decreasing blood pressure, studies show that the risk factor for cardiovascular disease is lower for pet owners than for non-pet owners. Similarly, elderly participants who had frequent HAI had lower levels of serum triglycerides (Wells, 2009). Additionally, in dog and cat owners HAI results in reductions in the frequency of minor physical ailments such as headaches, colds, and dizziness (Wells, 2009).

            The physical effects of animals are easy to explain. HAI decreases stress—disturbances in homeostatic balance—due to psychological factors (such as mental math). These decreases in stress can be directly linked to reductions in the sympathetic nervous system response, with corresponding decreases heart rate and blood pressure. In pet owners, these reductions can aid long-term health. In these pet owners, chronically high heart rate and blood pressure no longer strains the hearts, and this removed strain lowers risk for cardiovascular disease. Similarly, decreasing the sympathetic nervous system response allows the parasympathetic nervous system to function properly. This then aids the immune system, thereby reducing frequency of minor physical ailments associated with minor illnesses, such as headaches and colds. Thus, essentially, animals positively impact human health by decreasing stress to allow your body to return to that homeostatic balance that was knocked out of balance by the stressors.

            The psychological effects of animals are not quite as easy to explain. We know that petting a real animal leads to increased levels of several neurochemicals, including oxytocin, beta-endorphin, prolactin, and dopamine, as well as decreased cortisol levels (Odendaal, 2000). These data support the idea that HAI decreases the stress response. We just don’t really know how that happens. We do know that tactile stimulation is important in the stress-relieving effects, as the simple act of petting animals can lead to decreased heart rate and blood pressure (Vormbrock & Grossberg, 1988). However, we also know that the petting action is not enough to relieve stress, as petting a stuffed animal does not decrease stress (Shiloh, Sorek, & Terkel, 2003). Thus, while we know that HAI decreases the stress response to improve human health, we don’t know the mechanisms by which animals elicit this response.

            There are some limits to these beneficial effects of HAI. For example, if someone with an animal phobia interacts with an animal, the effects on stress will be counter-productive. However, for people who do like animals, spending an extra few minutes petting your dog—or even walking a dog at a shelter—can decrease your stress levels to improve your health.

           

References

Adamle, K. N., & Riley, T. A. (2010). Evaluating college student interest in pet therapy. Journal of American College Health, 57, 545-548. doi: 10.3200/JACH.57.5.545-548

Allen, K., Shykoff, B. E., & Izzo Jr., J. L. (2001). Pet ownership, but Not ACE inhibitor therapy, blunts home blood pressure responses to mental stress. Hypertension: Journal of the American Heart Association, 38, 815-820. Retrieved from http://hyper.ahajournals.org/content/38/4/815.full.pdf+html

Barker, S. B., Pandurangi, A. K., & Best, A. M. (2003). Effects of animal-assisted therapy on patients’ anxiety, fear, and depression before ECT. The Journal of ECT, 19, 38-44. Retrieved from http://ovidsp.tx.ovid.com.dml.regis.edu/sp-3.6.0b/ovidweb.cgi?WebLinkFrameset=1&S=HGPDFPGEEMDDALMHNCPKBFDCODGKAA00&returnUrl=ovidweb.cgi%3f%26Full%2bText%3dL%257cS.sh.18.19%257c0%257c00124509-200303000-00008%26S%3dHGPDFPGEEMDDALMHNCPKBFDCODGKAA00&directlink=http%3a%2f%2fgraphics.tx.ovid.com%2fovftpdfs%2fFPDDNCDCBFMHEM00%2ffs041%2fovft%2flive%2fgv012%2f00124509%2f00124509-200303000-00008.pdf&filename=Effects+of+Animal-Assisted+Therapy+on+Patients%27+Anxiety%2c+Fear%2c+and+Depression+Before+ECT.&pdf_key=FPDDNCDCBFMHEM00&pdf_index=/fs041/ovft/live/gv012/00124509/00124509-200303000-00008

Lefkowitz, C., Paharia, I., Prout, M., Debiak, D., & Bleiberg, J. (2005). Animal-assisted prolonged exposure: A treatment for survivors of sexual assault suffering posttraumatic stress disorder. Society & Animals, 13, 275. doi: 10.1163/156853005774653654

Odendaal, J. S. (2000). Animal-assisted therapy — magic or medicine?. Journal of

Psychosomatic Research, 49, 275-280. doi: 10.1016/S0022-3999(00)00183-5

Shiloh, S., Sorek, G., & Terkel, J. (2003). Reduction of state anxiety by petting animals in a controlled laboratory experiment. Anxiety, Stress & Coping: An International Journal, 16, 387-395. doi: 10.1080/1061580031000091582

Vormbock,  J. K., & Grossberg, J. M. Cardiovascular effects of human-pet dog interactions. Journal of Behavioral Medicine, 11, 509-517. doi: 10.1007/BF00844843

Wells, D. L. (2009). The effects of animals on human health and well-being. Journal of Social Issues, 65, 523-543. doi: 10.1111/j.1540-4560.2009.01612.x