Overview
Stress is the collection of physiological and psychological reactions that occur when an individual perceives a demand, challenge, or threat. It ranges from brief, adaptive reactions that improve performance to prolonged responses that can impair functioning and health. Stress involves how a person appraises a situation and the resources they have to respond; the same event can be experienced as manageable by one person and overwhelming by another.
Physiological mechanisms
Two central systems coordinate many stress responses: the sympathetic nervous system and the hypothalamic–pituitary–adrenal (HPA) axis. Activation of these systems releases signalling molecules and hormones, which prepare the body for immediate action and influence heart rate, respiration, metabolism and immune activity. While short-term activation supports adaptation, chronic activation can alter bodily systems and contribute to wear and tear.
Types and common causes
Stress is often categorized as acute (short-lived), episodic (recurrent) or chronic (persistent). Another useful distinction is between eustress, which can motivate and support growth, and distress, which impairs wellbeing. Common external causes include work demands, relationship difficulties, financial strain, major life events and environmental pressures. Internal contributors include expectations, coping style and personality traits.
Signs and symptoms
- Physical: headaches, muscle tension, gastrointestinal upset, sleep disruption.
- Emotional and cognitive: irritability, low mood, worry, poor concentration or memory.
- Behavioural: changes in appetite, withdrawal, increased substance use or risky behaviours.
Health effects and outcomes
Sustained stress is associated with effects on cardiovascular, metabolic and immune functioning and with higher likelihood of mood and sleep disorders. It can influence recovery from illness and interact with other risk factors. The presence and magnitude of effects vary with duration, severity, individual vulnerability and access to support.
Measurement and assessment
Stress is assessed with self-report questionnaires that measure perceived stress and life events, behavioural observation and biological markers such as heart rate variability and stress hormones. No single measure captures every aspect; clinical evaluation often combines methods to understand context and impact.
Coping, treatment and prevention
Coping approaches include problem-focused strategies (planning, time management), emotion-focused techniques (relaxation, cognitive reframing), social support and lifestyle measures such as regular physical activity, balanced sleep and healthy routines. When stress leads to persistent impairment, psychological therapy and medical evaluation may be appropriate. Preventive measures address sources of chronic strain and build resilience through skills training and supportive environments.
Distinctions and history
Stress is related to but distinct from clinical anxiety disorders; stress refers to responses to demands, while anxiety disorders involve persistent and impairing symptoms. The scientific study of stress expanded with early work describing stages of adaptation to prolonged threats. Contemporary perspectives emphasize individual appraisal, context, neurobiology and the balance between adaptive and harmful responses.