Stress and Physical Illness: The Hidden Biological Pathways Every Adult Should Know

The role of stress in physical illness

Stress is understood as a process in which environmental demands exceed an individual’s adaptive capacity. This mismatch produces psychological strain and biological changes that increase vulnerability to illness. Stress affects individuals across age, socioeconomic background and occupation. The factors that trigger stress are known as stressors. From an evolutionary standpoint, the human body is designed to respond to stress in ways that ensure protection from threats. When confronted with a potential problem, individuals evaluate its seriousness and assess whether they have the necessary resources to cope. When the problem is judged to be significant and coping resources are perceived as insufficient, the situation is experienced as stress. The appraisal and response pattern influence susceptibility to illness and overall well-being.

When a threat is perceived, the hypothalamus activates the body’s alarm system. For example, encountering a barking dog during a morning walk can trigger this process. Through neural and hormonal pathways, the adrenal glands release hormones such as adrenaline and cortisol. Adrenaline increases heart rate, elevates blood pressure and boosts energy. Cortisol raises glucose levels in the bloodstream, enhances the brain's use of glucose and increases the availability of substances that support tissue repair. Cortisol also suppresses nonessential functions during the fight-or-flight response, including digestion, reproduction and growth. It alters immune responses and communicates with brain regions that regulate mood, motivation and fear.

Prolonged or excessive stress disrupts both mental and physical functioning. It is therefore important to distinguish between different types of stress.

Eustress and Distress

Eustress refers to a positive, adaptive form of stress. It enhances performance, increases alertness and strengthens coping mechanisms. Research demonstrate that eustress as a healthy challenge that motivates action. This type of stress can sharpen athletic performance or enhance public speaking confidence by elevating energy and focus.

Distress occurs when stress exceeds coping capacity. It fatigues physiological systems and produces behavioural and physical difficulties. Distress is associated with overreaction, confusion, reduced concentration and performance decline.

Further, Research shows that short-term stress can temporarily enhance immune functioning, whereas chronic stress impairs immunity and increases susceptibility to illness.

Acute Stress

Acute stress is the most common type. It arises from immediate challenges such as examinations, job interviews or public presentations. Symptoms include increased heart rate, sweating, muscle tension and strong emotional reactions such as anxiety or anger. Although acute stress can heighten readiness and mental sharpness, excessive intensity or frequency can lead to fatigue and emotional strain.

Chronic Stress

Chronic stress persists over time and is linked to situations viewed as uncontrollable or inescapable. It presents as emotional exhaustion, reduced motivation and long-term health risks. Chronic stress is associated with cardiovascular disease, depression, anxiety and other chronic conditions. It is considered the most harmful form due to its cumulative effects on physical and psychological systems.

Stress and Physical Illness

The relationship between stress and illness is multifaceted. Susceptibility varies according to genetic predisposition, coping styles, personality characteristics and social support. Stress affects every major bodily system, including the musculoskeletal, respiratory, cardiovascular, endocrine, gastrointestinal, nervous and reproductive systems. Chronic activation of the stress response and prolonged exposure to cortisol can disrupt normal physiological processes and increase risk for numerous health problems, such as:

• • Anxiety
• • Depression
• • Digestive disturbances
• • Headaches
• • Muscle tension and pain
• • Cardiovascular disease, hypertension and stroke
• • Sleep disruptions
• • Weight gain
• • Difficulties with memory and concentration

Healthy Stress Management

Stressful events are part of daily life. Although individuals may not always be able to change the circumstances causing stress, they can manage their responses. Identifying stress triggers and maintaining physical and emotional well-being are central to effective coping. Evidence-based strategies include:

• • Maintaining a nutritious diet, regular exercise and adequate sleep
• • Practising relaxation techniques such as yoga, deep breathing or meditation
• • Journaling to process thoughts or record gratitude
• • Engaging in hobbies such as reading, music or recreational activities
• • Building supportive relationships and communicating with trusted individuals
• • Using humour and incorporating enjoyable moments
• • Volunteering or participating in community activities
• • Organising responsibilities and removing unnecessary tasks
• • Seeking professional counselling to develop coping skills

Unhealthy coping behaviours such as excessive alcohol use, smoking, drug use or overeating should be avoided. Individuals who notice increases in these behaviours should consult a healthcare professional.

References

Cohen, S., Kessler, R. C., & Gordon, L. U. (1995). Strategies for measuring stress in studies of psychiatric and physical disorders. In S. Cohen, R. C. Kessler, & L. U. Gordon (Eds.), Measuring stress: A guide for health and social scientists (pp. 3–26). Oxford University Press.

Lazarus, R. S. (1966). Psychological stress and the coping process. McGraw-Hill.

Salleh, M. R. (2008). Life event, stress and illness. Malaysian Journal of Medical Sciences, 15(4), 9–18. https://doi.org/10.1155/2008/22589633

Selye, H. (1956). The stress of life. McGraw-Hill.