Understanding the Concept of Stress: Types and Sources

Stress is something everyone experiences – before a deadline, during a conflict, or after an unexpected loss. But despite how familiar it feels, stress is a precisely defined psychological and physiological concept with a rich scientific history. Hans Selye, the Hungarian-Canadian endocrinologist widely regarded as the “father of stress research,” first introduced the term into medical science in 1936 to describe the body’s nonspecific response to any demand placed upon it. Understanding what stress actually is – and what drives it – is foundational to managing it effectively.

Where the concept of stress began 🔗

Before Selye’s landmark work, the scientific community understood the body’s response to injury as largely specific – each stressor caused its own distinct reaction. Selye was the first scientist to identify “stress” as underlying the nonspecific signs and symptoms of illness. As a medical student in Prague, he had noticed that patients with widely different diagnoses shared a strikingly similar cluster of complaints: fatigue, loss of appetite, diminished motivation, and a general sense of being unwell. He called this the “syndrome of just being sick.”

His laboratory experiments confirmed what his clinical observations had suggested. When he subjected rats to various harmful conditions – cold, physical restraint, toxic injections – each produced the same three-part biological response: enlarged adrenal glands, shrunken lymphatic tissue, and gastric ulcers. He named this the General Adaptation Syndrome (GAS). Selye proposed three stages of GAS: the alarm stage, in which the body prepares for fight or flight; resistance, in which the body adapts and works to maintain homeostasis; and exhaustion, where continued stress depletes the body’s resources and physical illness can follow.

The word “stress” itself has origins in physics, where it refers to the interaction between a force and the resistance to counter it. Selye was the first to bring this term into the medical lexicon, defining it as the body’s nonspecific response to any demand – pleasant or unpleasant.

Eustress vs. distress: not all stress is the same 🔗

One of Selye’s most significant later contributions was recognizing that stress is not inherently negative. It took him almost four decades to specify that not all stress reactions are equivalent, and that differences depend not just on the intensity of a stressor but on the individual’s perception of it.

Eustress: the positive side of pressure 🔗

The term “eustress” combines the Greek prefix eu- (meaning “good”) with the word “stress,” giving it the literal meaning of “good stress.” Eustress refers to a positive cognitive response to a stressor – one that motivates, energizes, and promotes growth. Preparing for a job interview, training for a marathon, or taking on a challenging new project can all generate eustress. This form of stress is associated with hope, active engagement, and higher life satisfaction. Importantly, eustress occurs when the gap between what one has and what one wants is slightly stretched but not overwhelmed – the goal feels challenging yet achievable.

Distress: when stress becomes harmful 🔗

Distress is the more familiar form of stress – the kind that drains rather than motivates. Selye defined distress as the negative, destructive type of stress triggered by unpleasant or harmful factors. It is associated with anxiety, withdrawal, and depressive behavior when it remains unresolved. Notably, both eustress and distress can be equally taxing on the body – the physiological stress response is largely the same in both cases. What differs is how the individual perceives and appraises the situation.

Three types of stress 🔗

Stress is categorized into various types based on duration, source, and response. The American Psychological Association (APA) identifies three primary types: acute stress, episodic acute stress, and chronic stress. Each has distinct characteristics, health implications, and pathways to management.

Acute stress 🔗

Acute stress is the most common type. It is a short-term stress response to immediate stressors or challenging situations, such as a sudden argument, a near-miss accident, or a looming presentation. The body activates its fight-or-flight response – releasing adrenaline, increasing heart rate, and sharpening focus – and then returns to baseline once the stressor passes. Acute stress can even arise from positive events like starting a new job or getting married. On its own, it is not inherently harmful; in fact, brief bouts of acute stress can sharpen alertness and performance.

Episodic acute stress 🔗

Episodic acute stress arises when a person experiences acute stress too frequently. This pattern is characteristic of individuals who lead chaotic or disorganized lifestyles, constantly facing deadlines, commitments, or interpersonal conflicts. It is also common in people who worry chronically, turning everyday uncertainties into sources of repeated alarm. Hostility, anger, anxiety, and depression frequently result from episodic stress, and the person often feels perpetually overwhelmed. Unlike chronic stress, episodes do subside – but they recur too often for the body to recover properly between them.

Chronic stress 🔗

Chronic stress is the most damaging type. It is ongoing, long-term emotional pressure that may result from circumstances a person has little or no control over – such as poverty, childhood trauma, or systemic discrimination. A defining feature of chronic stress is that the person does not know when the demands of the stressor will end, so they begin making accommodations just to get through each day – avoiding social situations, abandoning meaningful goals, or simply enduring. Chronic stress induces sustained activation of the sympathetic nervous system and the hypothalamic-pituitary-adrenal (HPA) axis, leading to elevated cortisol and epinephrine levels that over time contribute to cardiovascular disease, impaired immunity, sleep dysregulation, and psychiatric disorders.

Sources of stress: what are stressors? 🔗

A stressor is any event, experience, or environmental stimulus that causes stress in an individual – perceived as a threat or challenge, whether physical or psychological. Stressors are more likely to significantly affect health when they are chronic, highly disruptive, or perceived as uncontrollable. They broadly fall into four categories.

Physical stressors 🔗

Physical stressors are biological or bodily in nature. These include illness, injury, chronic pain, sleep deprivation, poor nutrition, and physical exhaustion. Physical environmental factors can affect a person’s biology or neurochemistry, meaning that even something as seemingly basic as an inadequate diet can reduce the body’s capacity to cope with stress when major life demands arise.

Psychological stressors 🔗

Psychological stressors originate within the mind – in thoughts, beliefs, and perceptions. Internal pressures such as perfectionism, fear of failure, low self-esteem, and unresolved trauma are potent sources of stress. Psychological stress can be caused by internal perceptions that lead an individual to experience anxiety or other negative emotions surrounding a situation they deem stressful – even when no external threat is objectively present. Cognitive appraisal plays a central role here: the same event can be deeply stressful to one person and entirely manageable to another.

Environmental stressors 🔗

Environmental stressors come from the surrounding physical world. Natural conditions such as extreme weather, changes in daylight, and environmental disasters can provoke anxiety and contribute to mental health disorders like seasonal affective disorder (SAD) and PTSD. Human-made environmental stressors – including noise, air pollution, overcrowding, and traffic – are among the most consistently studied for their effects on mood and cognitive performance. High population density in urban environments can lead to chronic stress through noise, pollution, and reduced social civility, gradually eroding mental wellbeing even without a single dramatic event.

Socio-cultural stressors 🔗

Socio-cultural stressors emerge from a person’s social roles, relationships, and the broader cultural environment they inhabit. Social stress is typically the most frequent type of stressor in daily life and affects people more intensely than other stressor types. It can arise from close relationships (family conflict, marital discord) as well as wider societal forces (discrimination, economic inequality, political instability). Lower socioeconomic standing tends to expose individuals to higher levels of both physical and social environmental stress – including crime, violence, discrimination, job loss, and family conflict – which combine to create a compounding stress burden over time.

Why the same stressor affects people differently 🔗

A key insight in stress research is that stressors do not operate uniformly. The relationship between psychosocial stressors and disease is affected by the nature, number, and persistence of the stressors, as well as by the individual’s biological vulnerability, psychosocial resources, and learned patterns of coping. Three factors are particularly important:

Nature of the stressor – Its severity, duration, predictability, and whether it is perceived as controllable all shape the stress response. Uncontrollable and unpredictable stressors tend to be the most damaging.

Individual tolerance – Personality traits like neuroticism increase stress reactivity, while characteristics like optimism and high self-esteem provide a buffer. Research shows that people with higher self-esteem have lower cortisol responses to acute stress, suggesting that internal psychological resources directly modulate the physiological impact of stressors.

Social support – Perhaps the most powerful moderating factor. Nurturing, supportive relationships allow individuals to better access their innate resources and respond to stress in positive ways, while the absence of social support not only fails to buffer stress but can itself become a source of it. Research consistently shows that those with strong social networks fare better after natural disasters, illness, and major life upheavals.

The broader significance of understanding stress 🔗

Stress is not simply a feeling – it is a complex interaction between external demands and internal resources. The framework Selye built in 1936, later refined with the distinction between eustress and distress, provides the conceptual foundation for how we now understand everything from workplace burnout to post-traumatic growth. Recognizing whether a stressor is acute, episodic, or chronic – and whether it stems from physical, psychological, environmental, or socio-cultural sources – is the first step toward responding to it with clarity rather than simply reacting to it. Not all stress is detrimental; some of it sharpens us, drives us forward, and builds resilience. The challenge lies in knowing which type we are dealing with – and choosing the right response.

What do you think? Reflecting on your own experience, do you find it easy to distinguish between eustress and distress in the moment – or does that clarity only come in hindsight? And considering the four categories of stressors, which type do you think has the most underestimated impact on everyday mental health?

References

1. https://pmc.ncbi.nlm.nih.gov/articles/PMC5915631/
2. https://www.ebsco.com/research-starters/history/hans-selye
3. https://onlinelibrary.wiley.com/doi/10.1002/bies.201900238
4. https://en.wikipedia.org/wiki/Eustress
5. https://www.ncbi.nlm.nih.gov/books/NBK541120/
6. https://www.choosingtherapy.com/types-of-stress/
7. https://sakuracounseling.org/services/acute-stress-vs-episodic-acute-stress-vs-chronic-stress/
8. https://remedypsychiatry.com/psychological-stress/
9. https://en.wikipedia.org/wiki/Psychological_stress
10. https://www.alliant.edu/blog/how-environmental-factors-impact-mental-health
11. https://www.ebsco.com/research-starters/environmental-sciences/environmental-factors-and-mental-health
12. https://en.wikipedia.org/wiki/Social_stress
13. https://pmc.ncbi.nlm.nih.gov/articles/PMC4343539/
14. https://pmc.ncbi.nlm.nih.gov/articles/PMC2568977/
15. https://www.healthandenvironment.org/resources/environmental-hazards/other-environmental-hazards/psychosocial-environment