Friday, February 15, 2013

Who Rescued Who?

A look into a particularly lovable stress reliever.

By Camille Longmore

       I’m sure you've seen this bumper sticker many times before.  It’s found commonly on cars with a cute grinning mutt's head hanging out the window. It becomes clear, then, that this is a rescue dog, and it is certainly grateful for its owner. But the phrase also suggests a strong sense of gratitude on the human’s part, to the extent where they consider themselves rescued. What could our pets possibly be rescuing us from?

       Well, as we all know, life is stressful. I, for one, can be a total stress case. There are several ways to deal with stress, as well as several ways to prevent it… here I shall shamelessly promote my own (as well as that of many others, judging by the abundance of those cute bumper stickers) favorite method: loving a pet.

       In order to discuss studies that have found positive correlations between owning a pet and decreased stress levels, we must first look at what causes stress.  When faced with a stressful situation that may, for example, elicit a “fight or flight” response (in the short term), or alternatively cause stress related changes in the body (in the long term), we produce a hormone called cortisol. Cortisol is produced in the adrenal glands situated atop our kidneys. Its release is controlled by the hypothalamus, an important part of our brain stem predominately involved in endocrine function. The hypothalamus secretes cortictropin-releasing hormone, triggering the neighboring pituitary gland to secrete another hormone, adrenocorticotropic hormone, which then travels to the adrenal gland via our blood and stimulates it, in turn, to produce cortisol (Pendleton, 2009) (our bodies are pretty awesomingly complicated, right?). How does this hormone specifically help us deal with a stressor, though? The next step in the pathway reveals this: cortisol stimulates a process called glycolysis, which is the breakdown of glycogen into glucose (sugar). Furthermore, it inhibits insulin, which is responsible for the uptake and storage of glucose. Therefore, this process provides an immediate and ready source of fuel for our muscles to perform any necessary tasks a “fight or flight” situation might demand of them (Pendleton, 2009).

J.A. Illingworth, University of Leeds

 So, it gets a little more complicated than what I discussed, but, if you find the hypothalamus and follow the pathway, you get the picture!

       There are then, obviously some benefits of cortisol secretion, as it aids our body in adjusting to a stressor. However, high or prolonged levels have several significant costs.  Elevated blood pressure, for example, is a side effect of this fight-or-flight response, as cortisol causes the narrowing of arteries and increased heart rate by increasing the sensitivity to other hormones, such as epinephrine and norepinephrine (thereby also increasing blood supply to our muscles aiding in the “fighting” or “fleeing”) (Tanaka et al., 2000). We, as humans (and particularly as Bio grad students...), live in an often high-stress, fast-paced lifestyle that can trigger frequent cortisol production-- and prolonged increased blood pressure obviously isn’t ideal! Furthermore, high levels of cortisol can reduce levels of serotonin in our brain (Young, 2007), and serotonin makes us happy!
       So how do we combat the seemingly inevitable elevated blood pressure and possible depression caused by stress? My answer, and, as I’ll now discuss, a very viable answer, is to get a pet.  

My personal little savior, Rue. 

       Karen Allen from the University of Buffalo, NY, has studied the benefits of animal companionship extensively. One study examined the effects of pet ownership in “hypertensive,” or high blood pressure, individuals (take note: these were all stockbrokers in New York…) who were all already taking the same blood pressure medication.  Everyone initially had to perform two psychologically stressful tasks-- mental arithmetic and giving a speech-- during which blood pressure and heart rate were measured (among other variables).  Furthermore, participant ratings of stress and coping were assessed both before and after each stressor. Half of the group was then instructed, in addition to their drug treatment, to obtain a dog or cat. Six months later, the tests were repeated, however this time, those with pets had their pet in the room with them.  Results found that, relative to those without pets, individuals with pets had significantly lower (by about half) physiological response scores (based on blood pressure, heart rate, etc.).  All had lower resting blood pressure (remember, they were all on the same blood pressure medication), but the addition of a social support lowered the responses to stress. Furthermore, the pet owners performed better on the stressful tasks, with a 92% correct performance compared to 75% in the non-pet owners.  All individuals in the initial trials (before pet acquisition) performed at 74%, strongly suggesting that the presence of pets provide the kind of unbiased social support that is critical to buffering physiological responses to stress (Allen et al., 2001). If that doesn’t convince you to promptly get a pet, the pet owner subjects later commonly described having a pet really “puts things into perspective,” and made them "better able to see what is really important.” When asked about the increased responsibility that comes with the animal, they responded that the benefits far outweighed the costs, and they would never give them up (Allen et. al, 2001). Apparently, when the results were published, many of the control group went out and got themselves a pet!

       Further studies support these findings; Allen later concluded that the presence of a pet is correlated with significant cardiovascular benefits among people with not only high blood pressure, but normal blood pressure (Allen, 2003). Another study by the same team of researchers used a physical stress test (the old “hold-your-hand-in-ice-cold-water-until-you-just-can’t-take-it-anymore-test”) to compare not only pet owners to non-pet owners, but the support of a pet, close friend, or partner during the trial. Non only did pet owners, relative to non-pet owners, have significantly lower heart rate and blood pressure levels, smaller increases from baseline levels, and faster recovery, but their best performances were when they were accompanied by their pet (over their friend or partner!) (Allen et al., 2002).

My 94 year old grandmother and her beloved feline companion. 

       Multiple other benefits have been studied, including the effects of owning a pet on the likelihood of depression in AIDS patients (Siegel et al., 1999), or in the elderly (Allen, 2003) (both revealed significantly lower depression in pet-owning individuals). Then, of course, there are the obvious ones, like how having a dog, for example, promotes exercise, or even social interactions with other humans; after all, they’re a great conversation starter! Oh… and there are some good looking guys at dog parks ladies….

No caption needed...

        The list of rewards from owning a pet goes on and on… obviously, then, we must appreciate our pets as much more than simply a companion.  If this is the case, let’s not be so selfish; let’s, instead, take a look at the picture from the animal’s side.  A unique study by Odendaal and Meintjes looked at the hormonal effects of positive human-dog interactions in both species; after all, it’s been established that there are benefits for the human, but how about our companion that we love so dearly? Are we giving back? Their results showed increased concentrations of some notable hormones, including the “good-feeling” inducers oxytocin and dopamine, in both species after “positive interspecies interaction” (i.e., a good time with your dog), yet cortisol, interestingly, decreased in humans only (Odendaal and Meintjes, 2003). Apparently humans are not only stressed out, but stressful! So go ahead and give your dog another treat today, he or she deserves it!!

Stress reliever extraordinaire!!

Literature Cited

Allen, K. 2003. Are pets a healthy pleasure? The influence of pets on blood pressure. Current Directions in Psychological Science 12: 236-239.

Allen, K., B.E. Shykoff, J.L. Izzo Jr. 2001. Pet ownership, but not ACE inhibitor therapy, blunts home blood pressure responses to mental stress. Hypertension 38:815-820.

Allen, K., J. Blascovich, W.B. Mendes. 2002. Cardiovascular reactivity and the presence of pets, friends, and spouses: The truth about cats and dogs. Psychosomatic Medicine 64:727-739.

Odendaal, J.S.J., R.A. Meintjes. 2003. Neurophysiological correlates of affiliative behaviour between humans and dogs. Veterinary Journal 165:296-301.

Pendleton, James. 2009. The Role of Cortisol in Human Physiology. 101: Anatomy and Physiology. 

Siegel J.M., F.J. Angulo, R. Detels, J. Wesch, A. Mullen. 1999. AIDS diagnosis and depression in the multicenter AIDS cohort study: the ameliorating impact of pet ownership. AIDS Care 11:157–169.

Tanaka, M., M. Yoshida, H. Emoto, H. Ishii. 2000. Noradrenaline systems in the hypothalamus, amygdala and locus coeruleus are involved in the provocation of anxiety: basic studies. European Journal of Pharmacology 405:397-406

Young S.N. 2007. How to increase serotonin in the human brain without drugs. Journal of Psychiatry and Neuroscience 32 (6):394–99

1 comment:

  1. Cute puppy Camille! I love when science gives us a more in-depth look into the reasons behind something we already know to be true! :)