My husband and I have a good friend from college, Dr. Michael Morales, who has a Doctorate in Biochemistry and teaches at the Jacobs School of Medicine & Biomedical Sciences at the University of Buffalo. He was a recent guest on Your Family Dog to talk about the immune and endocrine systems in dogs. (See: The Inside of Your Dog). We had a wide ranging discussion and touched on two topics that I asked him to write a bit more about. This week I am tackling the subject of stress and whether or not there is such a thing as optimal stress.
First of all, Mike gave a terrific definition of stress:
Stress is any stimuli that disrupts normal physiologic equilibria. Stresses can be divided into two broad categories. Neurogenic stresses are those perceived by the nervous system, like the mailman coming to your door every single day. Systemic stresses include injuries, excessive thirst, or starvation.
He goes on to add that despite the variability of the types of stress we (or our dogs) encounter, the body has “just one integrated stress response mediated by the sympathetic nervous system and the adrenal glands.” The adrenal glands secrete cortisol, which is always present in the blood stream, lasts a long time, and there is much more of it during times of stress. It is often thought of as the stress hormone but, “in reality, it is an anti-stress hormone” whose function is to help one cope with stress. Epinephrine is the other major adrenal hormone. Non-epinephrine from the sympathetic nervous systems pairs with epinephrine and,
These are the famous “fight or flight” hormones. They cause your puppy’s arousal when that mail man appears. Epinephrine doesn’t last long in the blood stream, just a minute or two compared to hours for cortisol. Interestingly, one of the functions of cortisol is to increase the amount of epinephrine. It doesn’t cause its release, but it allows more to be released at an increased frequency.
The important take away here is that there are both short response and long response hormones that are released to help us manage stress. So, if we have the internal mechanism to manage stress, why do we all instinctively know that chronically high stress is not good and can have some serious consequences? As Mike explains:
Exposure to high levels of cortisol in a puppy or even prenatally in the womb can cause psychological damage that can last long into adulthood. Cortisol influences genome function in a way that can be permanent and can potentially be transmitted across generations. Added to this is the revolution in our understanding of brain development, and one could conclude that the responsible puppy owner avoids stress at all costs, right? Of course, it’s not so simple. Remember, cortisol is always present, and in fact, we can’t live without it. So it turns out that there is a correct amount of stress.
Who knew? Well, many of us knew that a bit of arousal enhances learning, but we didn’t know how the hormones worked to enhance that learning. Mike continues:
The effects of cortisol can be thought of something like a bell curve. At the top of the curve is where you are likely to find a happy well-adjusted dog. Too much cortisol is associated with aggression and overly defensive behavior. Too little cortisol will leave your precious little bundle unable to cope with the normal stresses that invade the life of all living creatures.
So now it’s not your puppy’s stress you’re worried about, but you own, trying to figure out how to properly raise the little guy. Neurobiology has provided some good news as well. Throughout life, neurons are born and die, synapses are formed and disappear, axons and dendrites grow and are pruned. This suggests that there is considerable potential for reversing the effects of a stressful puppyhood than had been previously imagined. But it is important to understand that the longer intervention is delayed, the harder it will be to undo the consequences of excessive stress early in life. So do the best you can, and trust that a supportive environment will undo any of your inevitable mistakes.
So, when you are headed out the door with your puppy, keep in mind that some stress is necessary for your dog to grow into the well-adjusted adult dog that you can trust to handle the ups and downs of a dog’s life. Be sure to have a lot of wonderful treats on hand while you are exposing your puppy to the world, and use positive reinforcement training to build a happy, trusting dog, eager to learn new things. Be smart about where you take him before his puppy shots are finished, and don’t try to do too much at one time. A happy half hour walk to the play ground to meet a few children will likely do more for your pup than a 2 hour forced march through town!*
A final thought from Mike:
We’ve all heard of or know dogs who overcome the cruelest of circumstances to become a well-behaved and cherished family dog. The flip side is the dog raised in a loving secure home who ends up nasty and aggressive. Researchers have noticed this individual variation as well, and have seen it even in strains of mice in-bred to be genetically nearly identical. It used to be chalked up to the dreaded “experimental variation.” It is now understood that this extraordinary variability of outcome in the face of chronic stress is not some experimental artifact but a feature of complex organisms. Considerable effort continues to be expended to understand this effect.
In other words, do your best to help your puppy his best. And, remember, that we cannot control every situation, genetics are complex, environmental factors influence behavior, and unfortunately, sometimes bad things happen that will have long term effects.
But, on the other hand, sometimes we win the lottery.
*For more information on socializing your puppy please see: