Biological Aspects of Stress and Anxiety

This is the fourth installment on the topic of anxiety.

By necessity, this discussion of the biological aspects of anxiety will be limited to a simplified overview. If you would like a thorough discussion, allow me to direct you to “Neuroendocrine pharmacology of stress,” or “The Neuroendocrinology of Stress” or “The Neuropsychology of Anxiety: Reprise.” These are quite technical and not written for a general audience; van der Kolk is a little bit more accessible. For our purposes, it will be enough to get a general understanding of the mechanisms involved in anxiety and how we think and feel when they kick in.

It all starts when a real or perceived threat is sensed. According to Chrousos, the brain’s reaction is to activate the stress system. Oversimplifying things, the hypothalamic-pituitary-adrenal (HPA) axis is engaged. This is undeniably a good thing when the situation is truly threatening.

One result of the HPA kicking into gear is that hormones are sent out to the adrenal glands. The adrenal glands respond by releasing epinephrine, norepinephrine and cortisol. These act to bring on the fight/flight response

This is perfect because we are now poised to react to the threat.

Blood pressure and heart rate increases, reaction time improves, blood flows more heavily into the brain and skeletal muscles. The body breaks down its stores of energy to power the muscles and brain.

The immune system gets a booster shot (just in case we get wounded or harmed). As another precaution, the body’s internal painkillers (endogenous opioids) are released. This would help us to keep running or fighting even if injured.

Reproduction is not going to help us either fight or run away so the sex drive gets shut down. Having dinner or completing digestion of my last snack is not a priority in times of high level, immediate threats. So, the corticotropin-releasing hormone (CRH) element of the stress system decreases appetite and sometimes leads to the colon emptying its contents. Again, if we might not live to see tomorrow, it is not a clear priority to continue growing and, accordingly, the growth hormones are shut down.

This is great. We are suddenly on full alert and completely ready for action. We can focus more acutely on the threat and begin to deal with it effectively.

Bring on the lions and tigers and bears. I won’t even say “Oh, my!”

In the normal run of events, I slay the dragon and the threat is gone. According to Chrousos, when the threat ends, the hormone cortisol notifies the hypothalamus. The hypothalamus, in turn, shuts off the corticotropin-releasing hormone (CRH). The body begins to return to a more normal state.

But wait. Suppose there is no victory of this sort. Imagine that the threat is a looming foreclosure; an unpleasant boss; any kind of ongoing and for the most part unavoidable stressor. I can’t break out my sword and vanquish the soaring adjustable rate mortgage, the raging boss or whatever else.

More complicated, perhaps, are the instances when we ourselves are part of the stress. Let’s say that my interests in high school were exclusively girls and hand-held video games (the latter did not exist, really, at that time). Both of these are fine pursuits. But years later it would be difficult to put those talents on a resume detailing my job skills. In a tight job market, my lack of training and education and low self-esteem is part of the chronic stress of unemployment or low paying jobs.

van der Kolk writes that: “chronic and persistent stress inhibits the effectiveness of the stress response and induces desensitization.” If you think that doesn’t sound good, you’re right. And chronic stress and anxiety are what we’ll delve into in the next post. I’ll also cover how anxiety and panic attacks can result from the fight/flight response in a later post.

References for this post include (in no particular order): The Anxious Brain; NIH Backgrounder—Stress; emedicine; Why Zebras Don’t Get Ulcers; Neuroendocrine pharmacology of stress; The Neuropsychology of Anxiety: Reprise; Wikipedia; mentalhealth.about.com; The Neuroendocrinology of Stress.

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