Whether the weather

Julius Caesar, and the Roman Empire
Couldn’t conquer the blue sky…
Everywhere you go, you always take the weather with you
Neil & Tim Finn (Crowded House)

Not sure how it’s been in your corner of the world, but I can state with absolute certainty that the weather over the past four months has been causing a significant amount of grief to inhabitants of southeastern Canada.  We Canadians have developed the capacity to tolerate imprisonment in our igloos for eight months of the year, in large part because we expect to be paroled between May and August (and, assuming good behavior, maybe even September).  Moreover, we expect the meteorological authorities to sanction the sporting of Hawaiian shirts, tank tops, Bermuda shorts and open-toed sandals.  Well, not this year!  May, June and July have been witness to well-below average temperatures.  And the sun has been missing in action, a victim of the abundant precipitation we’ve experienced over this time.

Yup, most of my friends and colleagues claim to be more stressed after returning from their vacations then before they left.  But isn’t it a stretch to claim that inclement weather is stressful?  Actually, thinking whether the weather is a stressor helps to clarify some of the vagaries associated with the concept of stress.

First of all, let’s make one thing clear:  Stress is well defined, at least physiologically.  In the biological literature, the term was first used by the great Hans Selye, who borrowed it from the field of engineering.  In that discipline, stress is anything that compromises the integrity of a structure, as, for example, the force of gravity or of the wind on a building or a bridge.  Selye recognized that the very process of living can pose challenges for the well-being of a physiological organism, and these challenges were encompassed under the rubric of “stress”.  Stress on physical structures can often be handled structurally, for instance by insuring that the beams used to build a bridge are strong enough to resist the combined pressure of gravity and the vehicles that cross it.  In contrast, most life-stresses require energy expenditure for effective coping.  If you’re a pre-urban homo-sapiens, the stress of hunger means you have to get up off your derrière and do some serious hunting or gathering.  Same thing is true if you happen to stumble across a saber-toothed tiger in your pursuit of sustenance: without the necessary energy to run like hell, or fight like hell, you’re likely to end up as Tony the tiger’s afternoon snack.  And, assuming you successfully avoid Tony and find something to nibble on, you need to invest some energy to digest the fruits of your labor (pun intended).

Selye’s brilliance lies not only in his appropriation of the concept of stress, but also in identifying one of the primary systems that allows us to mobilize energy.  It’s called the hypothalamic-pituitary-adrenal (HPA) axis, and it works like this:  the challenges of life get recognized by the “higher” (i.e., thinking) parts of your brain, which informs the hypothalamus: “we’ve got a problem here, deal with it.”  So, the hypothalamus releases a substance called corticotrophin releasing hormone, which causes, among other things, the release of another hormone called andrenocorticotropin hormone (ACTH) from the pituitary.  Also among other things, ACTH travels to the adrenal glands, where it induces the release of cortisol, known in scientific circles as the mother of all stress hormones.  Cortisol is important in that it initiates the conversion of the body’s energy stores (i.e., sugars and fats) into actual energy, and this kinetic energy allows us to carry out the physical activities we need to in order to cope with the stress.

Selye defined stress as anything that will turn on the HPA axis.  It is a very clear, unambiguous and measurable definition of stress.  Moreover, defined in this way, stress is an essential part of life; indeed, without the HPA axis we wouldn?t be able to survive.  One way in which this is best illustrated is by appreciating that there is a natural rhythm to the HPA axis.  The cartoon below depicts normal cortisol levels as a function of the time of day.

Notice that cortisol levels rise as we wake up (to meet the challenges of the new day), reach a peak at lunch (digestion, again), fall in mid-afternoon (which explains the biological imperative responsible for the Siesta), rise again in anticipation of dinner, and then fall as we begin the descent into sleep. In short, cortisol levels recapulitulate the energy demands of living.

The intellectual quandaries one gets into when one talks about stress do not stem from Selye’s definition of stress, they originate when we start asking more questions about that definition. If stress is ultimately HPA activity, what turns on the HPA axis?  Clearly there are some physiological regulators of the axis:  as intimated above, hunger, is one, sex (the act, not the category) is another one, and infectious agents, such as the viruses that cause the flu, is a third.

There are many more that I could mention, but I think it’s time to get back to the main point.  Research over the past 70 years has demonstrated that we can turn on the HPA axis with entities that we consider to be more “psychological” then “physiological” in nature.  And it is this realization that explains why the weather can or cannot be a stressor.

Two of the four primary psychological activators of the HPA axis are:  being exposed to things we can’t predict, and being exposed to things we can’t control.  Actually, it’s even more subtle then this:  it is being exposed to things that we want to or feel we should be able to predict and control.  If your plans over your vacations are to spend two weeks catching up on all the DVDs you didn’t have time to watch, well, you could care less whether its rains cats and dogs 24/7.  If, on the other hand, you plan to spend a week hiking through the Adirondack Mountains, knowing what kind of weather to expect helps you to be make the contingency plans necessary to deal with it.  And notice that, for most people, being able to make plans imparts a modicum of control.

And herein lies the rub, at least for me.  What stressed me out the most about my holidays was not the amount of rain we experienced, but rather the unpredictability of when that rain would occur.  Most days were a chaotic blend of sun, rain, rain, sun.  We had very few days of total sun or of total rain.  So, you could never really plan for the day.  If you awoke to clouds and decided it was a perfect day for a Monopoly marathon, you started feeling guilty around 11 AM when the sun poked through and made the cottage a little too warm.  If you opened your eyes to sun first thing in the morning and decided it was the ideal day to paint the trim on the cottage or to take that 4 hour canoe trip, those 45 minutes of intense down pour that arrived around 1:15 were difficult to endure.

In retrospect, it turns out that we did most all of the things we wanted to do over the vacation, so it wasn’t the fact that we could not enjoy any of our planned activities.  Rather, it was the uncertainty about when to do them, and the prospect that the weather might rain on our parade right in the middle of the march.  It wasn’t just the bad weather, but the inability to predict when that bad weather would arrive.

That’s my take on whether the weather will make your life miserable.  But I could be wrong.  Two weeks ago, summer finally arrived.  After 5 consecutive days of hot, sunny and humid conditions ideal for outdoor activities, most everyone started bitching about it…

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Posted in Brain, Human.

Posted on 26 Aug 2009

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One comment to Whether the weather

  1. Dennis Jacques, R.N.
    On Feb 19th 2010 at 16:37

    Well reasoned! Can we not, however, argue successfully that the weather itself is a stressor? If hunger and the acts of digestion and sexual activity stress the body, is it not reasonable to infer that having to stand in 2 inches of slush, cleaning salt residue from the windshield of one’s automobile, in 35 F air, while near ice water falls upon us from the heavens may also stress the body? If this is the case, then it might reasonably be that the weather ITSELF causes disease.