40-2 How does stress make us more vulnerable to disease?

To study how stress, and healthy and unhealthy behaviors influence health and illness, psychologists and physicians have created the interdisciplinary field of behavioral medicine, integrating behavioral and medical knowledge. Health psychology provides psychology’s contribution to behavioral medicine. The subfield of psychoneuroimmunology, focuses on mind-body interactions (Kiecolt-Glaser, 2009). This awkward name makes sense when said slowly: Your thoughts and feelings (psycho) influence your brain (neuro), which influences the endocrine hormones that affect your disease-fighting immune system. And this subfield is the study of (ology) those interactions.

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If you’ve ever had a stress headache, or felt your blood pressure rise with anger, you don’t need to be convinced that our psychological states have physiological effects. Stress can even leave you less able to fight off disease because your nervous and endocrine systems influence your immune system (Sternberg, 2009). You can think of the immune system as a complex surveillance system. When it functions properly, it keeps you healthy by isolating and destroying bacteria, viruses, and other invaders. Four types of cells are active in these search-and-destroy missions (FIGURE 40.4).

Your age, nutrition, genetics, body temperature, and stress all influence your immune system’s activity. When your immune system doesn’t function properly, it can err in two directions:

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Stress can also trigger immune suppression by reducing the release of disease-fighting lymphocytes. This has been observed when animals were stressed by physical restraints, unavoidable electric shocks, noise, crowding, cold water, social defeat, or separation from their mothers (Maier et al., 1994). One study monitored immune responses in 43 monkeys over six months (Cohen et al., 1992). Half were left in stable groups. The rest were stressed by being housed with new roommates—3 or 4 new monkeys each month. By the end of the experiment, the socially disrupted monkeys had weaker immune systems.

Human immune systems react similarly. Some examples:

The stress effect on immunity makes physiological sense. It takes energy to track down invaders, produce swelling, and maintain fevers. Thus, when diseased, your body reduces its muscular energy output by decreasing activity and increasing sleep. Stress does the opposite. It creates a competing energy need. During an aroused fight-or-flight reaction, your stress responses divert energy from your disease-fighting immune system and send it to your muscles and brain. This renders you more vulnerable to illness. The point to remember: Stress does not make us sick, but it does alter our immune functioning, which leaves us less able to resist infection.

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We know that stress suppresses immune system functioning. What does this mean for people with AIDS (acquired immune deficiency syndrome)? As its name tells us, AIDS is an immune disorder, caused by the human immunodeficiency virus (HIV). Although AIDS-related deaths have decreased 29 percent since 2001, AIDS remains the world’s sixth leading cause of death and Africa’s number one killer (UNAIDS, 2013; WHO, 2013).

Ironically, if a disease is spread by human contact (as AIDS is, through the exchange of bodily fluids, primarily semen and blood), and if it kills slowly (as AIDS does), it can be lethal to more people. Those who acquire HIV often spread it in the highly contagious first few weeks before they know they are infected. Worldwide, some 2.3 million people—slightly more than half of them women—became infected with HIV in 2012, often without their awareness (UNAIDS, 2013). Years after the initial infection, when AIDS appears, people have difficulty fighting off other diseases, such as pneumonia.

Stress cannot give people AIDS. But could stress and negative emotions speed the transition from HIV infection to AIDS? And might stress predict a faster decline in those with AIDS? An analysis of 33,252 participants from around the world suggest the answer to both questions is Yes (Chida & Vedhata, 2009). The greater the stress that HIV-infected people experience, the faster their disease progresses.

Would efforts to reduce stress help control the disease? Again, the answer appears to be Yes. Educational initiatives, bereavement support groups, cognitive therapy, relaxation training, and exercise programs that reduce distress have all had positive consequences for HIV-positive people (Baum & Posluszny, 1999; McCain et al., 2008; Schneiderman, 1999). But compared with available drug treatments, the benefits have been small.

Although AIDS is now more treatable than ever before, preventing HIV infection is a far better option. This is the focus of many educational programs, such as the ABC (Abstinence, Be faithful, Condom use) program that has been used with seeming success in Uganda (Altman, 2004; UNAIDS, 2005). In addition to such programs that seek to influence sexual norms and behaviors, today’s combination prevention programs also include medical strategies (such as drugs and male circumcision that reduce HIV transmission) and efforts to reduce social inequalities that increase HIV risk (UNAIDS, 2010).

Stress does not create cancer cells. But in a healthy, functioning immune system, lymphocytes, macrophages, and NK cells search out and destroy cancer cells and cancer-damaged cells. If stress weakens the immune system, might this weaken a person’s ability to fight off cancer? To explore a possible connection between stress and cancer, experimenters have implanted tumor cells in rodents or given them carcinogens (cancer-producing substances). They then exposed some rodents to uncontrollable stress, such as inescapable shocks, which weakened their immune systems (Sklar & Anisman, 1981). Stressed rodents, compared with their unstressed counterparts, developed cancer more often, experienced tumor growth sooner, and grew larger tumors.

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Does this stress-cancer link also hold with humans? The results are mixed. Some studies find that people are at increased risk for cancer within a year after experiencing depression, helplessness, or bereavement (Chida et al., 2008; Steptoe et al., 2010). In one large Swedish study, the risk of colon cancer was 5.5 times greater among people with a history of workplace stress than among those who reported no such problems. This difference was not due to group differences in age, smoking, drinking, or physical characteristics (Courtney et al., 1993). Other studies, however, have found no link between stress and human cancer (Coyne et al., 2010; Petticrew et al., 1999, 2002). Concentration camp survivors and former prisoners of war, for example, do not have elevated cancer rates.

One danger in hyping reports on emotions and cancer is that some patients may then blame themselves for their illness: “If only I had been more expressive, relaxed, and hopeful.” A corollary danger is a “wellness macho” among the healthy, who take credit for their “healthy character” and lay a guilt trip on the ill: “She has cancer? That’s what you get for holding your feelings in and being so nice.” Dying thus becomes the ultimate failure.

It’s important enough to repeat: Stress does not create cancer cells. At worst, it may affect their growth by weakening the body’s natural defenses against multiplying malignant cells (Antoni & Lutgendorf, 2007). Although a relaxed, hopeful state may enhance these defenses, we should be aware of the thin line that divides science from wishful thinking. The powerful biological processes at work in advanced cancer or AIDS are not likely to be completely derailed by avoiding stress or maintaining a relaxed but determined spirit (Anderson, 2002; Kessler et al., 1991). And that explains why research has consistently indicated that psychotherapy does not extend cancer patients’ survival (Coyne et al., 2007, 2009; Coyne & Tennen, 2010).

40-3 Why are some of us more prone than others to coronary heart disease?

Depart from reality for a moment. In this new world, you wake up each day, eat your breakfast, and check the news. Political coverage buzzes, local events snap up airtime, and your favorite sports team occasionally wins. But there is a fourth story: Four 747 jumbo jet airlines crashed yesterday and all 1642 passengers died. You finish your breakfast, grab your books, and head to class. It’s just an average day.

Replace airline crashes with coronary heart disease, the United States’ leading cause of death, and you have re-entered reality. About 600,000 Americans die annually from heart disease (CDC, 2013). Heart disease occurs when the blood vessels that nourish the heart muscle gradually close. High blood pressure and a family history of the disease increase the risk. So do smoking, obesity, a high-fat diet, physical inactivity, and a high cholesterol level.

Stress and personality also play a big role in heart disease. The more psychological trauma people experience, the more their bodies generate inflammation, which is associated with heart and other health problems (O’Donovan et al., 2012). Plucking a hair and measuring its level of cortisol (a stress hormone) can help predict whether a person will have a future heart attack (Pereg et al., 2011).

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Type A PersonalityIn a now-classic study, Meyer Friedman, Ray Rosen-man, and their colleagues tested the idea that stress increases vulnerability to heart disease by measuring the blood cholesterol level and clotting speed of 40 U.S. male tax accountants at different times of year (Friedman & Ulmer, 1984). From January through March, the test results were completely normal. Then, as the accountants began scrambling to finish their clients’ tax returns before the April 15 filing deadline, their cholesterol and clotting measures rose to dangerous levels. In May and June, with the deadline past, the measures returned to normal. For these men, stress predicted heart attack risk. Blood pressure also rises as students approach everyday academic stressors (Conley & Lehman, 2012).

So, are some of us at high risk of stress-related coronary heart disease? To answer this question, the researchers who studied the tax accountants launched a nine-year study of more than 3000 healthy men, aged 35 to 59. The researchers first interviewed each man for 15 minutes, noting his work and eating habits, manner of talking, and other behavior patterns. Those who seemed the most reactive, competitive, hard-driving, impatient, time-conscious, supermotivated, verbally aggressive, and easily angered they called Type A. The roughly equal number who were more easygoing they called Type B. Which group do you suppose turned out to be the most prone to coronary heart disease?

Nine years later, 257 men had suffered heart attacks, and 69 percent of them were Type A. Moreover, not one of the “pure” Type Bs—the most mellow and laid back of their group—had suffered a heart attack.

As often happens in science, this exciting discovery provoked enormous public interest. After that initial honeymoon period, researchers wanted to know more. Was the finding reliable? If so, what was the toxic component of the Type A profile: Time-consciousness? Competitiveness? Anger?

More than 700 studies have now explored possible psychological correlates or predictors of cardiovascular health (Chida & Hamer, 2008; Chida & Steptoe, 2009). These reveal that Type A’s toxic core is negative emotions—especially the anger associated with an aggressively reactive temperament. When we are harassed or challenged, our active sympathetic nervous system redistributes bloodflow to our muscles, pulling it away from our internal organs. One of those organs, the liver, which normally removes cholesterol and fat from the blood, can’t do its job. Type A individuals are more often “combat ready.” Thus, excess cholesterol and fat may continue to circulate in their blood and later get deposited around the heart. Further stress—sometimes conflicts brought on by their own abrasiveness—may trigger altered heart rhythms. In people with weakened hearts, this altered pattern can cause sudden death (Kamarck & Jennings, 1991). Hostility also correlates with other risk factors, such as smoking, drinking, and obesity (Bunde & Suls, 2006). In important ways, people’s minds and hearts interact.

Hundreds of other studies of young and middle-aged men and women have confirmed the finding that people who react with anger over little things are the most coronar-prone. Suppressing negative emotions only heightens the risk (Kupper & Denollet, 2007). One study followed 13,000 middle-aged people for 5 years. Among those with normal blood pressure, people who had scored high on anger were three times more likely to have had heart attacks, even after researchers controlled for smoking and weight (Williams et al., 2000). Another study followed 1055 male medical students over an average of 36 years. Those who had reported being hot tempered were five times more likely to have had a heart attack by age 55 (Chang et al., 2002). Rage “seems to lash back and strike us in the heart muscle” (Spielberger & London, 1982).

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Type D PersonalityIn recent years, another personality type has interested stress and heart disease researchers. Type A individuals direct their negative emotion toward dominating others. People with another personality type—Type D—suppress their negative emotion to avoid social disapproval. The negative emotion these Type D individuals experience during social interactions is mainly distress (Denollet, 2005; Denollet et al., 1996). In one analysis of 12 studies, having a Type D personality significantly increased risk for mortality and nonfatal heart attack (Grande et al., 2012).

Effects of Pessimism and DepressionPessimism seems to be similarly toxic. Laura Kubzansky and her colleagues (2001) studied 1306 initially healthy men who a decade earlier had scored as optimists, pessimists, or neither. Even after other risk factors such as smoking had been ruled out, pessimists were more than twice as likely as optimists to develop heart disease (FIGURE 40.6).

Depression, too, can be lethal. Happy people tend to be healthier and to outlive their unhappy peers (Diener & Chan, 2011; Siahpush et al., 2008). Even a big, happy smile predicts longevity, as researchers discovered when they examined the photographs of 150 Major League Baseball players who had appeared in the 1952 Baseball Register and had died by 2009 (Abel & Kruger, 2010). On average, the nonsmilers had died at 73, compared with an average 80 years for those with a broad, genuine smile. People with broad smiles tend to have extensive social networks, which predict longer life (Hertenstein, 2009).

The accumulated evidence suggests that “depression substantially increases the risk of death, especially death by unnatural causes and cardiovascular disease” (Wulsin et al., 1999). After following 63,469 women over a dozen years, researchers found more than a doubled rate of heart attack death among those who initially scored as depressed (Whang et al., 2009). In the years following a heart attack, people with high scores for depression were four times more likely than their low-scoring counterparts to develop further heart problems (Frasure-Smith & Lesperance, 2005). Depression is disheartening.

Stress and InflammationDepressed people tend to smoke more and exercise less (Whooley et al., 2008), but stress itself is also disheartening:

As FIGURE 40.7 illustrates, both heart disease and depression may result when chronic stress triggers persistent inflammation (Matthews, 2005; Miller & Blackwell, 2006). After a heart attack, stress and anxiety increase the risk of death or of another attack (Roest et al., 2010). As we have seen, stress disrupts the body’s disease-fighting immune system, enabling the body to focus its energies on fleeing or fighting the threat. Yet stress hormones enhance one immune response, the production of proteins that contribute to inflammation. Thus, people who experience social threats, including children raised in harsh families, are more prone to inflammation responses (Dickerson et al., 2009; Miller & Chen, 2010). Inflammation fights infections; if you cut yourself, inflammation recruits infection-fighting cells. But persistent inflammation can produce problems such as asthma or clogged arteries, and worsen depression. Researchers are now uncovering the molecular mechanisms by which stress, in some people, activates genes that control inflammation (Cole et al., 2010).

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We can view the stress effect on our disease resistance as a price we pay for the benefits of stress (FIGURE 40.8). Stress invigorates our lives by arousing and motivating us. An unstressed life would hardly be challenging or productive.

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Psychological states are physiological events that influence other parts of our physiological system. Just pausing to think about biting into an orange section—the sweet, tangy juice from the pulpy fruit flooding across your tongue—can trigger salivation. As the Indian sage Santi Parva recognized more than 4000 years ago, “Mental disorders arise from physical causes, and likewise physical disorders arise from mental causes.” There is an interplay between our heads and our health. We are biopsychosocial systems.

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