Understanding the have-knots: The role of stress in just about everything

The great challenge in stress psychology — and the necessary precursor to developing interventions against stress’s harmful effects — has been understanding the mechanisms by which thoughts and feelings and other “mental” stuff can affect bodily health.

For many years, it was believed that the main causal link between stress and disease was the immune suppression that occurs when the body redirects its energy toward the fight-or-flight response. But recent research has revealed a far more nuanced picture.

Stress is known to actually enhance one important immune response, inflammation, and increasingly this is being seen as the go-between in various stress-related diseases.

Ordinarily, inflammation is how the healthy body deals with damaged tissue: Cells at the site of infections or injuries produce signaling chemicals called cytokines, which in turn attract other immune cells to the site to help repair it. Cytokines also travel to the brain and are responsible for initiating sickness behavior. Overactive cytokine production has been found to put individuals at greater risk for a variety of aging-related illnesses.

Cytokines may be an important mediator in the relationship between stress and heart disease. When the arteries feeding the heart are damaged, cytokines induce more blood flow, and thus more white blood cells, to the site. White blood cells accumulate in vessel walls and, over time, become engorged with cholesterol, becoming plaques; these may later become destabilized and rupture, causing heart attacks.

Cytokine action also has been implicated in the link between stress and depression. People suffering from clinical depression have shown 40–50 percent higher concentrations of certain inflammatory cytokines. And about 50 percent of cancer patients whose immune responses are artificially boosted through the administration of cytokines show depressive symptoms.

The close connection between inflammation and both depression and heart disease has led some researchers to theorize that inflammation may be what mediates the two-way street between these two conditions: Depression can lead to heart disease, but heart disease also often leads to depression.

Sleep may be part of this puzzle too, as disturbed sleep, which often goes with anxiety and depression, increases levels of proinflammatory cytokines in the body.

Not everyone responds the same way to stress. Personality traits like negativity, pessimism, and neuroticism are known to be risk factors for stress-related disease, as are anger and hostility.

In the late 1950s, Friedman and Rosenman identified a major link between stress and health with their research on the “Type A” personality: a person who is highly competitive, aggressive, and impatient. This personality was found to be a strong predictor of heart disease, and later research clarified the picture: The salient factors in the relationship between the Type A personality and health are mainly anger, hostility, and a socially dominant personality style (for example, tending to interrupt other people while they are talking).

When negative emotions like anger are chronic, it is as if the body is in a constant state of fight or flight.