Understanding Stress: Concepts and Health Impacts

Stress

Stress occurs when "demands exceed the personal and social resources the individual is able to mobilize."

Homeostasis

Maintaining stability in the body despite external changes.

Allostasis

The process of allowing changes as needed to deal with stimuli.

Allostatic load

The wear and tear on the body from repeated stress exposure, shifting homeostasis to a new baseline.

Bodily systems mobilized in response to stress

Energy is mobilized, digestion slows, immune system weakens, growth/tissue repair slows, memory is impacted, testosterone levels decrease, pain sensitivity lowers.

Adrenal gland release during stress

Cortisol, epinephrine, and adrenaline.

Effects of adrenaline

Increases heart rate.

Stress effects on the gut

Stress can change the composition and function of gut bacteria.

Three stages of General Adaptation Syndrome (GAS)

1️⃣ Alarm: Threat detection, body unprepared. 2️⃣ Resistance: Body mobilizes resources to cope. 3️⃣ Exhaustion: Resources depleted, body returns to or falls below baseline.

Divisions of the autonomic nervous system

- Sympathetic Nervous System (fight or flight, releases adrenaline/epinephrine). - Parasympathetic Nervous System (rest and digest, promotes relaxation).

Role of the HPA axis in stress

Brain detects stress → hypothalamus releases CRH → pituitary releases ACTH → adrenal glands release cortisol → cortisol mobilizes energy.

Negative feedback regulation of cortisol levels

When cortisol reaches high levels, the hippocampus signals the brain to stop producing it.

Trouble stopping cortisol production

Due to allostatic load, their stress response system is dysregulated.

Chronic stress impact on the immune system

Suppresses adaptive immunity, promotes inflammation, increases susceptibility to disease.

Diseases contributed to by chronic stress

Cardiovascular disease, weakened immune response, faster disease progression (e.g., HIV).

Psychological factors influencing stress resilience

Coping mechanisms, positive relationships, cognitive reframing, sleep, exercise, relaxation techniques.

Cortisol

A bloodborne hormone that mobilizes energy in response to stress.

Measuring cortisol levels

Through urine, blood, saliva, and hair samples.

Effects of cortisol on the body

- Increases blood sugar. - Weakens the immune system. - Interrupts cognition and memory. - Increases sympathetic nervous system activity. Impairs blood vessel function, triggers cholesterol plaque buildup

Internal validity

How well a study establishes a cause-effect relationship.

External validity

How well study findings apply to the real world.

Mason Factors triggering HPA stress response

Uncontrollability, unpredictability, novelty, and ego involvement (e.g., embarrassment).

Acute vs. chronic stressors in research

Acute stressors show clear cortisol changes; chronic stressors reflect long-term effects on health.

Trier Social Stress Test (TSST) components

Baseline video (3 min), prep (5 min on post-college plans), presentation (5 min, evaluated by experts), mental math (5 min, increasing difficulty), followed by a recovery period with cortisol measurement.

Mason Factors influencing stress response

Uncontrollability, Unpredictability, Ego Involvement, Novelty

Uncontrollability

A factor that contributes to stress.

Unpredictability

A factor that contributes to stress.

Ego involvement

A factor that contributes to stress.

Novelty

A factor that contributes to stress.

Cortisol peak duration

The length of time cortisol levels remain elevated after a stressor.

Cortisol recovery to baseline

The process of cortisol levels returning to normal after a stressor.

Cortisol response with age

Greater cortisol response with age and pubertal stage (teens more stressed than children).

Parental support and stress response

10-year-olds had the highest stress response with a stranger; 15-year-olds had more stress response with their parent than with a stranger.

Flatter cortisol response

Observed in breast cancer survivors with high fatigue, suggesting reduced ability to mobilize energy.

Structural stigma

Measured by factors like state policies, public opinion toward sexual minorities, proportion of Gay-Straight Alliances per high school, and density of same-sex partners in the state.

Blunted cortisol response

Caused by high structural stigma due to chronic stress.

Vicarious discrimination

Witnessing discrimination against others, which can shape stress responses over time.

Cortisol levels during the day

Lowest during sleep, spike after waking (Cortisol Awakening Response, CAR), and gradual decline across the day with small spikes for meals.

Steeper diurnal slope

Considered healthier as it reflects better adaptation to daily needs.

Sympathetic Nervous System (SNS)

Part of the ANS responsible for 'Fight or Flight' responses, increasing heart rate, sweating, and energy mobilization.

Parasympathetic Nervous System (PNS)

Part of the ANS responsible for 'Rest and Digest' functions, slowing heart rate and promoting digestion.

SNS and PNS response to stress

SNS increases and PNS decreases for immediate survival; chronic activation can lead to health risks.

Vagus nerve

The 10th cranial nerve that relays information across the body and maintains homeostasis.

Vagal brake

The role of the PNS in inhibiting SNS activity to regulate stress.

Higher PNS activity

Leads to more positive emotions (calmness, cheerfulness) and better emotion regulation.

ANS activity change over lifespan

Infants have high SNS and low PNS; childhood to adolescence sees increasing PNS and decreasing SNS; older adults have lower PNS and higher SNS.

Factors leading to greater SNS and lower PNS activity

Noise pollution, air pollution, trauma, major life stressors, and poor sleep quality.

Chronic SNS activation and cardiovascular disease

Contributes to hypertension, arterial wall damage, immune system response forming fatty plaques, and increased heart disease risk.

Measuring PNS activity

Resipratory Sinus Arrhythmia (RSA)

Higher RSA → Higher PNS activity

High Frequency heart rate variability is measured as RSA. It reflects the variation in heart rate associated with breathing, indicating autonomic nervous system function.

Heart Rate Variability (HRV)

Higher variability = higher PNS activity.

Pre-Ejection Period (PEP)

Heart contractility.

Electrodermal Activity (EDA)

Hand sweat.

Catecholamines in urine

SNS chemicals.

Moment-to-Moment SNS Activity

Electrodermal Activity (EDA) (hand sweat).

Resting autonomic activity

Higher PNS activity and lower SNS activity at rest.

Autonomic system response to stress

PNS declines, SNS increases.

Autonomic reactivity and cardiovascular disease risk

Greater SNS responses in daily life could reflect greater cardiovascular disease risk.

PNS declines and mental health in children

Greater declines in PNS activity tend to be linked to better mental health in children.

Reciprocal Sympathetic Activation

Characterized by high SNS and low PNS.

Reciprocal Parasympathetic Activation

Shows low SNS and high PNS.

Coactivation

Involves high activity in both SNS and PNS.

Coinhibition

Involves low activity in both SNS and PNS.

Chronic activation of the autonomic system

Can lead to hypertension and other risks.

Improving PNS activity

Deep breathing, cold exposure, humming/singing, slow-tempo music, meditation, tai chi, massage, probiotics, omega-3, and regular sleep.

Immune system

A collection of cells and organs that detect and protect against foreign substances (bacteria, viruses, parasites, fungi).

Two branches of the immune system

Innate (non-specific) and adaptive (specific) immunity.

Innate immune system

First line of defense, responds quickly to a range of pathogens.

Macrophages

Immune cells that engulf pathogens and release cytokines.

Cytokines

Chemical messengers that coordinate the immune response.

Acute inflammation

Features include heat, pain, redness, and swelling.

Helpful acute inflammation

It recruits immune cells to fight infection.

Inflammaging

Increased chronic inflammation with age, linked to disease risk.

Chronic stress and inflammation

Sustained stress causes chronic low-grade inflammation, increasing disease risk.

Adaptive immune system

Provides a targeted defense against specific pathogens.

T cells

Immune cells that direct responses and kill infected cells.

B cells

Immune cells that produce antibodies.

Antigen

A toxin or foreign substance that triggers an immune response.

Common methods for measuring immune function

Cellular (cell counts), protein (CRP levels), cytokine signaling, genetic transcription factors.

CRP

Used for measuring inflammation and cardiovascular risk.

Trier Social Stress Test (TSST)

Measures immune response to acute stress.

Vaccination studies

Assess immunity by measuring antibody responses to vaccines.

Acute stress and the immune system

Increases inflammation to prepare for injury.

Chronic stress impact on immunity

Leads to prolonged inflammation and reduced antiviral defense.

Conserved Transcriptional Response to Adversity (CTRA)

A pattern of increased inflammatory gene activity and decreased antiviral defenses due to chronic stress.

Social support and immune function

Higher social support is linked to lower inflammation and better immune health.

What is measured at the cellular level in immune studies?

Counting different type of cells, such as CRP.

What is the function of CRP?

Important immune-related protein; high levels indicate inflammation and increased risk of cardiovascular disease.

Cytokines

Chemical messengers in immune responses.

How doe researchers measure immune function at the genetic level?

Measuring transcription factors, which influence gene expression and immune cell production.

Immediate Stress

Immune system, HPA Axis, and SNS all respond to this type of stress.

In Vivo

Experiments that are done and observed in the body; Trier Social Stress Test (EDA), Inflammatory Injection Test(Immune Activation), Vaccination studies(Antibody Production), Endotoxin Injection (Inflammation)

Ex Vivo

Blood sample of a patient that is manipulated with a endotoxin to study immune response outside the body.

Why focus on innate immunity studies?

Applies broadly to general population (External Validity)

IL-6

pro-inflammatory cytokine that increases under stress and affects illness recovery.

Conserved Transcriptional Response to Adversity (CTRA)

Increased inflammatory gene activity and decreased antiviral gene activity - an evolutionary response developed to survive physical threats, but is a liability in terms of modern stress.