Stress changes the body’s physiology and the way people think and behave, which can raise disease risk over time. Health psychology focuses on these mind–body links and why chronic stress is especially harmful.

Core idea: stress as a health risk factor

Stress is not only a feeling; it is a set of biological responses that can be adaptive short-term but damaging when frequent, intense, or prolonged.

Diagram of the hypothalamic–pituitary–adrenal (HPA) axis showing how a stress signal triggers sequential hormone release: CRH from the hypothalamus, ACTH from the pituitary, and cortisol from the adrenal glands. This helps explain how psychological stress can become a sustained physiological state through endocrine signaling and feedback. Source

Across many conditions, stress increases susceptibility to disorders and disease by disrupting cardiovascular, immune, and nervous system functioning and by encouraging risky coping behaviors.

Pathways from stress to illness

• Physiological pathway: stress hormones and autonomic arousal alter organs and body systems.

• Cognitive-emotional pathway: worry, rumination, and negative appraisal amplify arousal and interfere with recovery.

• Behavioral pathway: sleep loss, substance use, inactivity, and poor adherence to medical advice increase health risk.

Cardiovascular effects: stress and hypertension

Stress activates the sympathetic nervous system (SNS) and increases catecholamines (e.g., epinephrine), raising heart rate and blood pressure.

Body-wide diagram comparing sympathetic and parasympathetic regulation of key organs (eyes, lungs, heart, digestive system, and more). The sympathetic side summarizes classic fight-or-flight changes (e.g., increased heart rate and mobilized energy), clarifying how autonomic activation can repeatedly load the cardiovascular system under chronic stress. Source

When this pattern is repeated (especially with chronic stress), blood vessels experience more wear, and resting blood pressure can trend upward.

Key mechanisms linking stress to hypertension include:

• Repeated vascular activation: frequent SNS-driven constriction increases strain on artery walls.

• Stress hormones: cortisol influences metabolism and can contribute to abdominal fat and other cardiovascular risk markers.

• Indirect behavioral effects: stress-related smoking, high-sodium convenience eating, and reduced exercise can maintain high blood pressure.

Pain and headaches: why stress often hurts

Stress is strongly linked to headaches, particularly tension-type headaches and stress-triggered migraines in susceptible individuals. Stress can increase pain through:

• Muscle tension: sustained contraction in the neck, jaw, and scalp.

• Heightened arousal and vigilance: increased attention to bodily sensations can intensify perceived pain.

• Sleep disruption: poorer sleep lowers pain tolerance and slows recovery.

• Rebound cycles: pain increases worry, which increases stress, which increases pain.

Immune suppression: stress and vulnerability to illness

A central health consequence of stress is immune suppression, especially under chronic stress conditions. Stress-related hormonal changes can reduce the efficiency of immune responses, making it easier for infections to take hold and harder for the body to repair damage.

How stress can suppress immunity:

• Cortisol effects: prolonged cortisol exposure can reduce aspects of inflammatory and antiviral responding, weakening the body’s defenses.

• Reduced immune cell activity: stress can blunt protective actions of certain white blood cells.

• Slower healing: the immune system plays a major role in tissue repair; when stressed, wound repair processes can be less efficient.

This immune impact helps explain why, during demanding life periods, some people get sick more often or recover more slowly.

Stress and susceptibility to disorders and disease

Stress functions as a broad risk factor rather than a single-cause explanation. It can contribute to:

• Onset: raising vulnerability to developing certain physical and psychological conditions.

• Exacerbation: worsening symptoms in existing conditions (e.g., increasing pain, fatigue, or flare-ups).

• Maintenance: sustaining unhealthy habits and keeping the body in a prolonged state of physiological activation.

Important qualifiers for AP Psychology:

• Duration matters: acute stress can be adaptive; chronic stress is more consistently linked to disease risk.

• Recovery matters: effective down-regulation (relaxation and sleep) helps restore balance after stress.

• Individual differences matter: appraisal, coping style, and available support influence how strongly stress affects health.