Stress, The Brain, and Neuroplasticity

[David Baxter PhD]

Science Says This Is How Stress Affects the Brain​

by Courtney Telloian, PsychCentral.com
January 12, 2022

Chronic stress can reduce the brain’s size and even alter its DNA, but building a collection of coping tools could help counter these changes.

Stress isn’t inherently bad. Your stress response can help you avoid and survive potentially life threatening situations — but chronic stress can be a bit trickier.

If you’re constantly dealing with high levels of stress, the way your brain responds to it may change over time. These brain changes can affect your mental health and leave you prone to future stress and its effects.

But because of the brain’s plasticity — its ability to change and adapt — it’s possible to change how you respond to stress and lessen its effects on your brain.

Your brain on stress​

Stress can have both short- and long-term effects on the brain.

It all starts with your amygdala and stress response, commonly called fight, flight, or freeze responses — a reaction to an acute, or short-term, stressor.

For example, losing control of your car on an icy road or having a sudden confrontation with an angry family member can both cause your stress response to be activated in any of the three ways.

This stress response starts in the brain in your amygdala, a part of the brain involved with emotions such as fear. The amygdala sends a danger signal to the hypothalamus, the part of your brain that regulates many key bodily functions like body temperature and heart rate.

The hypothalamus then activates your sympathetic nervous system, the “alert“ response, which comes with an adrenaline boost and kicks your body into high gear so you’ll be ready to face the potential threat.

But after fight, flight, or freeze, your hypothalamus activates another stress response system: the hypothalamic-pituitary-adrenal (HPA) axis. The HPA axis works to keep your sympathetic nervous system engaged and on high alert.
On a physical level, this releases cortisol — the stress hormone — into your system.

While cortisol helps your mind and body handle stressful events in the short term, chronic stress can cause the HPA axis to become dysregulated. It may release cortisol in fits and starts in response to more events, meaning you’re feeling stressed more of the time.

And that’s when stress can take a toll on your mind and body.

How does chronic stress physically change the brain?​

Brain size​

Chronic, or long-term, stress can affect the size of your brain and even its genetic makeup.

Many of these physical changes happen as a result of high cortisol levels and changes to the way your brain functions under prolonged stress.

For instance, according to 2008 researchTrusted Source, long-term exposure to cortisol can shrink the prefrontal cortex, the area of your brain involved with planning and making decisions.

Research from 2016 found higher cortisol levels were directly linked to a lower volume of many parts of the prefrontal cortex.

Stuck on repeat​

One theory is that over time, emotional responses to stress become a vicious cycle in the brain.

If your brain keeps activating a stress response in more situations, it may cause the parts of your brain that get more use — like the amygdala — to strengthen. Other areas that get less use as a result — the prefrontal cortex — can become smaller with less use.

Smaller capacity for memory and emotional regulation​

Long-term stress is also linked to a smaller hippocampus, the part of the brain responsible for emotion processing and memory.

Gene expression​

In addition, stress can affect your brain’s DNA through epigenetics, a process in which your environment interacts with and can suppress or activate family genes.

For example, according to 2016 researchTrusted Source, stress caused by childhood trauma is connected with epigenetic changes to the brain’s DNA and HPA axis.

These changes then impact your brain’s — and your — response to stress.

Chronic stress on the body and brain​

Long-term stress and exposure to cortisol can change the way your brain functions over time, noticeably impacting your memory, emotions, and mental health.

Difficulty processing emotions​

Emotional regulation is a key function of the hippocampus, but long-term stress can get in the way of this process.
In particular, the hippocampus is negatively impactedTrusted Source when stress reduces the plasticity of the brain.

When the hippocampus has less flexibility to change and adapt, it can lead to having a harder time managing emotions. You might experience more emotional highs and lows or feel like you’re at the mercy of strong emotional responses you can’t control.

When chronic stress impacts emotional regulation, it can also make you more likely to fall into thinking patterns like:

• self-criticism
• rumination, or getting into a rut of thinking about a particular stressor
• frequent worry
• feelings of loneliness

Executive functioning challenges​

Executive functioning is a set of skills involved with:

• self-control
• memory
• ability to adapt

This skill set comes from your prefrontal cortex, but it also involves the hippocampus and amygdala.

Research from 2017 highlights that strong emotions and stress can reduce executive functioning skills like reasoning and problem-solving. Long-term stress can lower your ability to learn and remember information as well.

Some researchers suggest these decreases in executive function are caused by an overactive HPA axis triggered by chronic stress.

Mental health conditions​

Chronic stress can change your brain in ways that make you more prone to developing mental health conditions like:

• Depression. Chronic stress that reduces the volume of the hippocampus may lead to major depressive disorder, according to 2019 researchTrusted Source.
• Anxiety disorders. Research from 2020Trusted Source highlights how exposure to high levels of stress over time can cause the amygdala to release the stress response too often, which can manifest as an anxiety disorder.
• Post-traumatic stress disorder (PTSD). According to research from 2017, long-term stress can cause both PTSD and chronic pain in a similar way. It also links PTSD to reduced volume of the hippocampus, amygdala, and prefrontal cortex.

Research from 2019 also suggests the high cortisol levels caused by chronic stress could play a role in brain conditions like dementia and Alzheimer’s disease.

How can you reverse the effects of stress on the brain?​

Chronic stress can cause you to view more situations as stressful, as well as limit the ways you’re able to respond to stressors.

Developing new ways of reacting to stress could help you build new connections in your brain that, over time, help you cope better. Approaches include:

• Practicing meditation. Research from 2019 found that 4 days of meditation resulted in changes to the brain that made it more resilient against stress. Even after 3 months, participants had maintained their new mental strength.
• Using prebiotics. A 2017 animal study suggests prebiotics — found in many fermented foods — could help people manage stress-related behaviors by keeping the paths on the brain-gut axis healthy and clear.
• Trying mindfulness-based stress reduction. 2016 research found that 8 weeks of mindfulness-based stress reduction increased activity in the hippocampus and prefrontal cortex while decreasing activity in the amygdala, helping with emotional regulation.
• Going for a quick jog. Running for just 10 minutes can help boost executive functioning and increase blood flow to the prefrontal cortex.
• Working with a therapist. Forms of talk therapy such as cognitive behavioral therapy (CBT) could make the amygdala less reactive, meaning it could slow down your fight, flight, or freeze responses to stress and allow you to form new ways to manage stressors.

Recap​

Sometimes we develop a pattern of responding to stress that makes the brain more easily influenced by stress. These changes can lead to memory issues, mental health conditions, or difficulties managing emotions.

Addressing your stress response is more complicated than simply reversing these brain changes, but certain brain training exercises, including many mindfulness-based approaches, could help you increase your brain’s positive response to stress.

 

[Daniel E.]

When I think of executive functioning, I like to think of pilots. They don't have the luxury to panic or get distracted. They have to stay relatively calm under pressure or else it is too hard to think clearly if there is an emergency like engine failure. So they train and train by exposing themselves to feared situations in simulators.

Pilots are also trained to avoid multi-tasking. So there is the "sterile cockpit" rule where pilots are not allowed to chit-chat while preparing for take-off or landing.