Stress and the Immune System

The Link Between Stress and Illness

Stress doesn't just make you feel bad — it can actually make you physically sick. The key mechanism is the immune system. When stress impairs how your immune system works, your body becomes more vulnerable to disease.

What is the Immune System?

The immune system is your body's defence force. It guards against attackers from both outside (like viruses and bacteria) and inside (like abnormal cells). The field that studies the connection between the mind, the brain, and the immune system is called psychoneuroimmunology. This field specifically examines how stress affects immune functioning.

How the Immune System Works

The main soldiers of the immune system are white blood cells (leucocytes) . They identify and destroy foreign bodies called antigens (such as viruses). They also trigger the production of antibodies — proteins that neutralise specific threats.

There are several types of white blood cells, each with a distinct job:

• T cells — destroy invaders directly. A special subtype, T-helper cells, increases overall immunological activity. These are the cells attacked by the Human Immuno Deficiency Virus (HIV), which causes AIDS.
• B cells — produce antibodies.
• Natural killer cells — fight both viruses and tumours.

Stress and Natural Killer Cells

Stress can reduce natural killer cell cytotoxicity — that is, the ability of these cells to kill their targets. This is a major problem because natural killer cells are crucial for defence against infections and cancer.

Reduced levels of natural killer cell cytotoxicity have been found in people under high stress, including:

• Students facing important examinations
• Bereaved persons
• Those who are severely depressed

Social Support Protects the Immune System

Studies show that immune functioning is better in individuals who receive social support. Having people to rely on buffers the harmful effects of stress on the immune system.

The Sequence: From Stress to Illness

The textbook presents a clear chain of events:

1. Negative emotions (depression, hostility, anger, aggression) arise from psychological stress.
2. These emotions trigger the release of stress hormones.
3. Stress hormones weaken the immune system.
4. A weakened immune system leads to poor mental and physical health.

This sequence is depicted in Figure 3.4 of the textbook, titled "Relation of Stress with Illness".

Negative Emotions and Their Consequences

Negative emotion states are of particular concern in the study of stress and health. Long-term stress increases the incidence of psychological disorders such as panic attacks and obsessive behaviour. Worries can become so intense that they surface as a frightening, painful physical sensation — which can be mistaken for a heart attack.

People under prolonged stress are more prone to:

• Irrational fears
• Mood swings
• Phobias
• Fits of depression, anger, and irritability …