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What is Stress?

  • We all know it, and face it pretty much every day in our lives. It’s a reaction that’s both physical and psychological, triggered by certain stimuli called stressors. However, stress isn’t always a bad thing – small levels of stress can help with things like motivating us to do things. 

  • Acute Stress: Acute stress is a short term and immediate reaction to a stressor. This is common when we see a threat or a challenge, and in response, our body will release hormones to trigger the fight or flight reaction (or freeze). The thing about acute stress is that once the stressor is resolved or disappears, the body will go back to normal. 

  • Chronic Stress: Chronic stress is long term, and typically occurs due to prolonged issues or situations. This happens if these stressors are either continuous and persistent, or repeated multiple times over a certain time frame – the body’s stress response stays activated, and leads to larger general health problems. 

  • What causes stress: Stressors can come in a variety of different forms 

    • External events: work, school, relationship, major life changes

    • Internal: beliefs, perceptions, coping abilities – some people are naturally more prone to negative thought patterns, perfectionism included

    • Environmental factors: noise, crowding, living condition

Symptoms:

  • Physical: Headaches or migraines, muscle tension or pain, fatigue and low energy, upset stomach, nausea, or digestive issues, rapid heartbeat or chest pain, trouble sleeping (insomnia or excessive sleeping), weakened immune system (frequent colds, infections)

  • Emotional: Anxiety or excessive worry, irritability or mood swings, feeling overwhelmed or helpless, depression or persistent sadness, difficulty relaxing or calming down, low self-esteem or self-doubt

  • Cognitive: Difficulty concentrating or making decisions, memory problems, racing thoughts or constant worrying, negative thinking patterns

  • Behavioral: Changes in appetite (overeating or undereating), social withdrawal or isolation, procrastination or avoiding responsibilities, increased use of alcohol, drugs, or caffeine, nail-biting, fidgeting, or other nervous habits

Hormones and Neurotransmitters:

Hormones are molecules that make up a part of our endocrine system, and they are responsible for acting as chemical messengers to transmit information through long distances in our bodies. Neurotransmitters are similar, except they are short distance molecules that transmit signals from neuron to neuron (in the gap called a synapse).  

  • Cortisol: It’s a hormone that is commonly known as the stress hormone – it’s released by the adrenal glands (they're on the kidneys) in response to stressors. To release these hormones, the HPA (hypothalamic pituitary adrenal axis) is activated. Prolonged exposure to high cortisol levels can have negative effects like mood disorders, reduces immunity, and impairs our cognition.

  • Adrenaline (Epinephrine): Adrenaline is a hormone that is also released by the adrenal glands during the fight or flight response – it prepares the body physically to respond to the stimuli. For example, this hormone will increase things like heart rate, blood pressure, and energy, as well as making us feel more awake and increasing our strength. Chronic stress and high adrenaline levels can make someone more prone to anxiety and physical decline. 

  • Dopamine: Dopamine is a neurotransmitter associated with reward, motivation, and pleasure. Stress can affect dopamine levels, particularly in chronic stress situations. Low dopamine levels can contribute to feelings of apathy, lack of motivation, and even depressive symptoms. Stress can also disrupt the brain's reward circuitry, making it harder to experience pleasure and satisfaction.

  • Serotonin: Serotonin helps regulate mood, sleep, and appetite. Stress can disrupt serotonin production and receptor function, leading to feelings of anxiety, depression, and irritability. Chronic stress can contribute to serotonin imbalances, which may increase susceptibility to mood disorders

How Stress Disrupts Sleep Cycles:

Stress can disrupt sleep, and poor sleep can make us more susceptible to stress. This disruption primarily occurs through the hypothalamic-pituitary-adrenal (HPA) axis and the release of stress hormones like cortisol. Also, some background: Our sleep occurs in cycles, typically 5 per night, each lasting about 90-120 minutes. Throughout the night, we go through different stages during the cycles, those being: Wake, REM (rapid eye movement), and Stages -4. 

  • Increased Cortisol Levels: Normally, cortisol follows a daily rhythm—low at night and peaking in the morning to help us wake up. However, chronic stress keeps cortisol levels elevated at night, making it difficult to fall and stay asleep.

  • Hyperarousal and Insomnia: Stress keeps the brain in a state of heightened alertness, increasing activity in the amygdala (fear response) and reducing activity in the prefrontal cortex (rational thinking). This imbalance leads to difficulty calming down before bed.

  • Reduced Slow-Wave Sleep (Deep Sleep): Stress decreases deep sleep (Stage 3), which is essential for physical recovery, memory consolidation, and emotional regulation.

  • Increased REM Sleep Disruptions: High stress can lead to fragmented REM sleep (the stage associated with dreaming and emotional processing), which is linked to increased mood instability and anxiety

How Genetic Variations Influence Stress Resilience or Vulnerability:

Each person is built with different genetic sequences – that means that in terms of stress, people may react in different ways. 

  • COMT Gene: It’s responsible for coding for an enzyme that breaks down dopamine, especially in areas like the prefrontal cortex. If this gene is expressed more heavily, then dopamine is cleared faster, making some individuals better at handling acute stress. On the other hand, if there is low COMT activity, then dopamine lingers longer, which leads to more anxiety under stress, but also better memory. 

  • BDNF Gene: This gene codes for a protein that supports the growth of our neurons (neuroplasticity). There’s a variation of this gene called Val66Met has been linked to reduced stress resilience, which means that people who do have this variant have a higher chance of developing anxiety and depression in response to prolonged stress. 

  • FKBP5 Gene: This gene helps to regulate the HPA axis, which controls the release of cortisol. Some variants of this gene may lead to higher cortisol reactivity, which increases the risk of PTSD and chronic stress related illnesses. 

  • 5-HTTLPR Gene: This gene is related to serotonin reuptake, where the short variant lowers serotonin reuptake efficiency; this may lead to anxiety and depression under stress. People who have the long variant have the opposite response, and are more resilient under stress.

How Stress Affects the Brain:

  • The amygdala: it’s a region of the brain that’s important for processing emotions like fear and anxiety. When our brains are stimulated by certain stressors, the amygdala becomes hyperactive, which means it has more activity than usual. The activity of the amygdala means that our emotional reactions to stimuli are increased beyond normal levels, including the negative reactions. If we face chronic stress, the amygdala becomes activated for longer than necessary, which causes impaired emotional regulation and increased response to emotional stressors. 

  • Prefrontal cortex: Stress can also impair the ability of the prefrontal cortex to work properly, which impairs certain functions like decision making, problem solving, and impulse control. Chronic stress in particular can make these symptoms worse. This happens through a hormone cortisol , which in times of stress, reduces communication to and from the prefrontal cortex, leading to some of the symptoms mentioned above.

  • Hippocampus: The hippocampus is responsible for everything that has to do with memory, like creating them. In times of chronic stress, the hippocampus can become damaged again from the increase in cortisol, which ultimately hurts our short and long term memory – it becomes harder to remember information and even learn new information! Sometimes, the hippocampus itself can shrink, leading to cognitive decline.

Other Physical Responses:

  • Hypothalamic-pituitary-adrenal (HPA) axis

    • This is our body’s central stress response system, where it is responsible for regulating how we react to stressors and maintaining homeostasis by releasing various molecules we call hormones. 

    • The process: First, corticotropin releasing hormone (CRH) is released by the hypothalamus, which activates the pituitary gland. The pituitary gland then releases adrenocorticotropic hormone (ACTH) into the bloodstream, which travels to the adrenal glands. The adrenal glands trigger the release of stress hormones, specifically, cortisol. In a normal human body, this should function in something we call a negative feedback loop, where high levels of cortisol signal the rest of this system to stop producing so much CRH and ACTH. However, in cases of chronic stress, this feedback loop breaks in a way, and cortisol levels become dysregulated. 

    • If the HPA axis is hyperactive (excess cortisol) , it can lead to conditions like anxiety, PTSD, and depression. Typically, high levels of stress causes a hyperactive HPA axis. A hypoactive HPA axis (too low cortisol) can lead to things like burnout, chronic fatigue, and atypical depression. 

  • The “fight-or-flight” response vs. the “freeze” response

    • Many people are familiar with fight or flight: when you see a stimulus, does your body tell you to run or face it? This response causes our bodies to react in a very specific set of ways -> increase heart rate and blood pressure, dilated pupils (better vision), faster + shallower breathing, glucose release for energy. These are all responses that are meant to prepare us for some immediate threat.

    • The freeze response happens when someone feels overwhelmed by fight or flight (like they can’t choose), and instead nothing happens. This typically happens with helplessness, or extreme levels of fear. Someone experiencing the freeze response might be unable to move, involuntarily, as well as experience a drop in blood pressure, blurry vision, and lower cortisol production (to reduce any emotion). This is the body’s alternative attempt at survival. 

  • The gut-brain connection: how stress affects digestion and microbiome

    • Digestion: stress can cause problems with the way we digest food – that means we may digest faster or slower than usual. Also, the processes that happen during digestion may be affected, like nutrient absorption. Chronic stress can decrease the amount of digestive enzymes secreted, which harms nutrient absorption. Also, stress may cause the gut lining to weaken, which allows toxic substances to enter into the bloodstream – this condition is called leaky gut. 

    • We all have certain strains of bacteria in our gut. However, stress can disrupt what species of bacteria are present; this increases the risk of having an imbalance of bad bacteria over the good bacteria. Conditions like irritable bowel syndrome or inflammatory bowel disease may worsen. Finally, the good bacteria in our gut is responsible for producing certain neurotransmitters like serotonin, which regulates our mood. A gut microbiome imbalance may lead to increased risk of anxiety and depression.

Neuroscience-Based Stress Management Techniques:

  • Mindfulness and meditation 

    • Mindfulness and meditation practices have been shown to induce structural and functional changes in the brain. Studies suggest that regular meditation increases gray matter density – gray matter is made up of  in the prefrontal cortex and hippocampus while reducing activity in the amygdala, which is responsible for fear and stress responses. These changes help regulate emotions, reduce anxiety, and improve overall mental well-being.

  • Exercise and neuroplasticity

    • Physical activity promotes neuroplasticity, the brain's ability to reorganize and form new neural connections. Exercise increases the release of brain-derived neurotrophic factor (BDNF), a protein that supports neuron growth and resilience. Additionally, aerobic exercise reduces cortisol levels, enhancing mood and cognitive function while mitigating the detrimental effects of stress.

  • Breathing techniques and the vagus nerve

    • Controlled breathing exercises, such as diaphragmatic breathing and resonance breathing, activate the vagus nerve, which plays a key role in the parasympathetic nervous system. This activation leads to reduced heart rate, lower blood pressure, and a calm mental state. Deep breathing also regulates cortisol levels and promotes relaxation by shifting the body from a stress-induced fight-or-flight mode to a restorative state.

  • Social support and oxytocin’s role in stress reduction

    • Social connections play a critical role in stress regulation. Interpersonal support increases the release of oxytocin, a hormone that fosters bonding and mitigates stress responses. Oxytocin inhibits amygdala activity and reduces cortisol levels, promoting emotional stability and resilience. Engaging in meaningful social interactions, such as spending time with friends and family, can be a powerful buffer against stress and its psychological effects.

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