Stress

Stress is part of all of our lives at one point or another. Things can be going along just fine, and then, you hit a traffic jam. What is stress? Where does it come from? And how does it affect us?

Stress can happen during positive events—childbirth, planning a marriage, playing in a championship sports game. But its nature is generally negative, and in large doses, can weaken and then severely impact our immune system and overall health.

Even regions of our brain can undergo stress-related physical changes. So where does all of this come from? Stressors are anything in our environment that place demands on a person or threaten their well being. These can range from cataclysmic events, such as natural disasters and terrorism, to everyday annoyances that prevent us from doing or getting what we want when we want it.

The body's response to stress is influenced by how we perceive the stressor, and how much control we think we have to deal with it. In primary appraisal, we assess whether or not an event or situation is threatening. For example, during primary appraisal, you might look at a bill you just received as threatening if there isn't any money in the bank to cover it.

During secondary appraisal, we determine whether or not we are in control and if we have resources to deal with the stressor. Using the same example, if you realize you won't get paid before the bill is due, you may feel trapped and unable to cope. It's our perception of whether or not we have control over the perceived threat—will I be able to pay the bills or pass the exam?—that influences our response.

In the brain, the stress response is centered on a system of interconnected structures that are together called the HPA axis, short for Hypothalamus, Pituitary, and Adrenal. The HPA energizes the body's fight or flight response to stressful stimuli and prepares us to take action. Brain activation to a threat occurs in the hypothalamus, which releases neurotransmitters to simulate the pituitary gland.

The pituitary secretes a stress hormone called a ACTH, which stands for adrenocorticotropic hormone. ACTH enters the bloodstream and stimulates the adrenal glands atop the kidneys. It's the adrenal glands that release the stress hormones which lead to a range of responses throughout the body, including effects on regions of the brain, such as the hippocampus, where stress negatively impacts our ability to form new long term memories.

In addition to affecting the hippocampus, one of the things that happens is that the amygdala, in contrast to the hippocampus, is perked up by stress. So just as the hippocampus is kind of shutting down, the amygdala is perking up. And because the amygdala is driving the stress response, it becomes an endless cycle. So as long as the stress is there, the amygdala will continue to cause the hypothalamus and pituitary and adrenal to release the stress hormones.

The HPA axis initiates a physical response meant to prepare the body to face a threat—our fight or flight response. In the 1930s, Hans Selye discovered that the physical response is the same, no matter what the source of stress. He called this the General Adaptation Syndrome, or GAS.

Cortisol increases the amount of glucose in the blood so that the body has more fuel at the ready.

Cortisol is the classic stress hormone. It then enters your bloodstream and goes to the body and causes various kinds of metabolic activities, but also goes to your brain. The initial affect in your brain is to sharpen your response, make you more alert and attentive, to help you deal with the stress you're facing.

Heart rate increases, blood pressure rises—the HPA axis triggers a whole slew of responses.

But as the level of cortisol builds up in your brain, it becomes a little bit too much. It's a little bit too much of a good thing. So your brain can't handle this overload of cortisol that is a consequence of prolonged stress or very intense stress.

Prolonged stress can lead to a weakened immune system, a perilous road toward serious illness.

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Stressors can roll into one another. Circulating hormones in the body do not disappear as soon as one stressor is removed. They can color an entire day or longer, affecting mood over time.

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