The nature of stress

Many researchers have struggled to agree on a single, clear definition of stress. One approach is to define stress as a demanding or threatening situation - such as having a high-stress job, living in crowded conditions, or enduring long commutes. These are called stimulus-based definitions because they treat stress as an external cause of certain reactions. A limitation of stimulus-based definitions is that people differ in how they perceive and respond to the same event. For example, a diligent student who studies thoroughly may feel less stress during final exams than someone who is unprepared.

Another way to conceptualize stress focuses on the physiological responses that occur when people face demanding or threatening conditions. This is called a response-based definition. One well-known description from an endocrinologist defined stress as the body’s reaction to any demand, whether pleasant or unpleasant. However, response-based definitions can be confusing because some bodily reactions (e.g., an increased heart rate) also occur during positive events, such as an unexpected raise or promotion.

A useful way to define stress is to treat it as a process: someone perceives an event and reacts to it as overwhelming or harmful to their well-being. A key part of this perspective is appraisal, meaning how we evaluate or interpret potentially difficult or threatening experiences (often called stressors). These appraisals shape the emotional and behavioral responses that follow.

Two kinds of appraisals are especially significant:

• Primary appraisal: This is the initial judgment about how much potential harm or danger a stressor poses. A situation may be labeled a threat if one thinks it may cause harm or negative outcomes, or it may be viewed as a challenge if it seems to offer chances for growth or gain.
• Secondary appraisal: This occurs when the situation is seen as a threat. It involves assessing what coping strategies are available and how successful they might be.
• Self-efficacy - the belief in one’s ability to carry out a task - plays a large part in whether one sees a threat as devastating or manageable.

Different types of stressors

• Cataclysmic events: Large-scale disasters that are hard or impossible to predict (e.g., major conflicts, natural disasters, terror attacks).
• Personal events: Notable life changes like having a baby, beginning or ending a relationship, moving to a new home, getting or losing a job, or dealing with severe illness or loss of someone close.
• Daily stressors: Routine stresses faced regularly, such as dealing with slow traffic, managing finances, or keeping up with household chores.

Effects of stress on psychological functions

Stress isn’t always harmful. Sometimes it can be beneficial and motivating, which is known as eustress (good stress). In moderate amounts, stress can enhance performance - for example, an athlete may use pregame stress as energy, or a student may feel a helpful level of pressure before a test.

When stress rises beyond this optimal level, it becomes distress. Distress is associated with exhaustion, burnout, and declining performance. If intense stress continues over time, it may also harm overall health.

Stress outcomes / response to stressors

• Physiological: The fight-or-flight response is a common reaction to perceived threats. The sympathetic nervous system and the endocrine system prepare the body for action. This includes a surge of epinephrine and norepinephrine from the adrenal glands, which elevates heart rate, expands pupils, and increases respiration. The hypothalamic-pituitary-adrenal (HPA) axis also becomes active and releases cortisol, often called the stress hormone. Cortisol can help the body meet immediate challenges, but prolonged elevated levels can weaken the immune system.

• Emotional: Persistent exposure to stressors can undermine overall well-being and may contribute to conditions like PTSD, anxiety disorders, or depression.

• Behavioral: People respond to stressful circumstances in different ways. Some address the problem directly, while others avoid or numb distress through substances or excessive screen time.

Managing stress (e.g., exercise, relaxation, spirituality)

Social support is a major resource for managing stress. Support may come from individuals or from groups (e.g., spiritual or special-interest communities).

Exercise (both aerobic and anaerobic) is known to improve physical and mental health, which can make people more resilient under stress. Techniques such as yoga, meditation, and relaxation are also widely used to reduce stress. One approach, the relaxation response technique, combines relaxation and a mantra while sitting quietly, which helps lower sympathetic arousal.

Another method, biofeedback, uses electronic tools to measure neuromuscular or autonomic activity and provides real-time visual or audio feedback. This feedback helps people learn to regulate processes that are usually involuntary. Biofeedback has been effective for problems such as tension headaches, high blood pressure, and phobias.