Stress continues to be a major American health issue, according to the American Psychological Association. More than one-third of adults report that their stress increased over the past year. Twenty-four percent of adults report experiencing extreme stress, up from 18 percent the year before.

It’s well-known that stress can be a detriment to overall health. But can stress actually change the physiology of the brain? Science says yes.

Defining Stress

The National Institute of Mental Health defines stress as simply “the brain’s response to any demand.” Given that definition, not all stress is bad. It is simply a response. How harmful it ultimately depends on its intensity, duration and treatment.

Stress takes a variety of forms. Some stress happens as the result of a single, short-term event — having an argument with a loved one, for example. Other stress happens due to recurring conditions, such as managing a long-term illness or a demanding job. When recurring conditions cause stress that is both intense and sustained over a long period of time, it can be referred to as “chronic” or “toxic” stress. While all stress triggers physiological reactions, chronic stress is specifically problematic because of the significant harm it can do to the functioning of the body and the brain.

Leading Causes of Stress

Stress occurs for a number of reasons. The 2015 Stress in America survey reported that money and work were the top two sources of stress for adults in the United States for the eighth year in a row. Other common contributors included family responsibilities, personal health concerns, health problems affecting the family and the economy.

The study found that women consistently struggle with more stress than men. Millennials and Generation Xers deal with more stress than baby boomers. And those who face discrimination based on characteristics such as race, disability status or LGBT identification struggle with more stress than their counterparts who do not regularly encounter such societal biases.

Physiological Effects of Stress on the Brain

Stress is a chain reaction. “When someone experiences a stressful event, the amygdala, an area of the brain that contributes to emotional processing, sends a distress signal to the hypothalamus,” Harvard Health Publications of Harvard Medical School explains. “This area of the brain functions like a command center, communicating with the rest of the body through the nervous system so that the person has the energy to fight or flee.”

This “fight-or-flight” response is responsible for the outward physical reactions most people associate with stress including increased heart rate, heightened senses, a deeper intake of oxygen and the rush of adrenaline. Finally, a hormone called cortisol is released, which helps to restore the energy lost in the response. When the stressful event is over, cortisol levels fall and the body returns to stasis.

Effects of Chronic Stress on the Brain

While stress itself is not necessarily problematic, the buildup of cortisol in the brain can have long-term effects. Thus, chronic stress can lead to health problems.

Cortisol’s functions are part of the natural process of the body. In moderation, the hormone is perfectly normal and healthy. Its functions are multiple, explains the Dartmouth Undergraduate Journal of Science. In addition to restoring balance to the body after a stress event, cortisol helps regulate blood sugar levels in cells and has utilitarian value in the hippocampus, where memories are stored and processed.

But when chronic stress is experienced, the body makes more cortisol than it has a chance to release. This is when cortisol and stress can lead to trouble. High levels of cortisol can wear down the brain’s ability to function properly. According to several studies, chronic stress impairs brain function in multiple ways. It can disrupt synapse regulation, resulting in the loss of sociability and the avoidance of interactions with others. Stress can kill brain cells and even reduce the size of the brain. Chronic stress has a shrinking effect on the prefrontal cortex, the area of the brain responsible for memory and learning.

While stress can shrink the prefrontal cortex, it can increase the size of the amygdala, which can make the brain more receptive to stress. “Cortisol is believed to create a domino effect that hard-wires pathways between the hippocampus and amygdala in a way that might create a vicious cycle by creating a brain that becomes predisposed to be in a constant state of fight-or-flight,” Christopher Bergland writes in Psychology Today.

Effects of Stress on the Body

Chronic stress doesn’t just lead to impaired cognitive function. It can also lead to other significant problems, such as increased risk of heart disease, high blood pressure and diabetes. Other systems of the body stop working properly too, including the digestive, excretory and reproductive structures. Toxic stress can impair the body’s immune system and exacerbate any already existing illnesses.

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Plasticity and the Brain: The Body’s Recovery System

Plasticity, or neuroplasticity, refers to the ways that neural pathways are able to re-form in the brain. It’s true that these pathways — like the one between the hippocampus and the amygdala — can get severely damaged due to constant exposure to stress, but such changes are not necessarily permanent. While stress can negatively affect the brain, the brain and body can recover.

Young adults, especially, are able to recover from the effects of stress, according to Proceedings of the National Academy of Sciences (PNAS). Age has a direct correlation with the reversibility of stress-related damage. It’s much more difficult for older adults to regain or create new neural pathways than their younger counterparts.

That’s not to say all hope is lost for older adults. PNAS points out that “interventions,” or activities that combat stress’ wear-and-tear on the brain, are effective regardless of age. Interventions including activities like exercising regularly, socializing and finding purpose in life enable plasticity.

It can seem like stress is an inevitable part of life, but chronic stress can have real and significant consequences on the brain. Understanding these effects and how to combat them can help promote overall health.

Understanding How Stress Affects the Brain

Professionals working in health and human services or psychology have the opportunity to help others manage their stress effectively and understand how stress affects the brain. Touro University Worldwide offers a variety of fully online degree programs at the bachelor’s, master’s and doctoral level that prepare students for careers in these fields.