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Stress is the response of an organism to novel or threatening situations that are unpleasant in character. In the 1930s physiologist Walter Cannon described how the sympathetic nervous system reacts to threatening situations.

According to Cannon, a chemical called "sympathin" made the organism ready to run away or fight. Sympathin is what we now call adrenaline or epinephrine. When released into the bloodstream and nervous system, it provokes a general activation of the sympathetic division of the autonomic nervous system, the fight or flight reaction.

We are all familiar with the effects of adrenaline. The heart beats faster, a person may perspire more, fatigue and tiredness vanishes, muscular activity becomes easier, and reactions become quicker.

Over the short term, this is an adaptive response that may help an organism survive. However, if the reaction continues too long, it can take a toll on an organism.

What is evidence that stress can affect healing?

For example, people involved in the care of relatives with Alzheimer's Disease do not heal as quickly when wounded. "Caregivers took an average of 9 days or 24% longer than controls to completely heal a small, standardized wound" (Kiecolt-Glaser, Page, Marucha, MacCallum, and Glaser, 1998). This is one of many findings showing that stressful life events can have adverse effects on health.

The effects of stress are duplicated almost exactly by stimulants such as amphetamines and cocaine (Antelman, Eichler, Black, and Kocan, 1980). Both stress and stimulant drugs produce heavy releases of cortico­sterones, the "stress hormones."

Both stress and stimulant drugs increase heart rate and other signs of activity in the sympathetic nervous system. They cause animals to engage in repetitive, stereotyped activity.

Eventually this high level of activation leads to "burn-out." If amphetamines are consumed to excess, they can cause delusions of persecution, agitation, and hallucinations.

MacLennan and Maier (1983) offer a variety of evidence suggesting that stress can mimic the effects of abusing amphetamines or cocaine. For example, a stressful life event can re-awaken a paranoid psychosis in a former amphetamine addict who now abstains from the drug.

Hans Selye (1907-1982) started the modern era of research into stress. In 1950, Selye addressed the American Psychological Association convention. He described a theory of stress-induced responses that become the standard model of stress for the next several decades.

How did Selye discover the stress response?

Selye's discovery of the stress response was an accident. He was doing research on the effect of hormone injections in rats. Initially he thought he detected a harmful effect from the hormones, because many of the rats became sick after receiving injections.

However, when Selye used a control group of rats, injected only with a neutral solution containing no hormones, he observed that they became sick, too. As it turned out, the rats were traumatized by being handled and given injections.

The rats, if they could give self-reports, would probably say, "I thought I was about to die." This extreme distress led to health problems such as ulcers. Selye coined the term "stressor" to label a stimulus that had this effect.

What is the immediate response of rats to being handled?

The immediate response to stress is the release of adrenaline into the blood. "Mild stressors such as opening a cage door or handling a rat produces an eightfold increase in plasma epinephrine [adrenaline] concentrations" (Axelrod and Reisine, 1984).

Selye proposed a three-stage pattern of response to stress that he called the General Adaptation Syndrome (GAS) . He proposed that when the organism first encountered a threat, it responded with an alarm reaction.

What were the three stages of Selye's General Adaptation Syndrome?

This is followed by a recovery or resist­ance stage during which the organism repairs itself and stores energy. If the stress-causing events continue, exhaustion sets in.

That third stage became known as burn-out. Classic symptoms of burn-out include loss of drive, emotional flatness, and (in humans) dulling of responsive­ness to the needs of others.

Common Stressors

Each phase of life has stressors (stimuli that cause stress). In college, typical stressors are cramming for tests, worry­ing about social relationships, or trying to work at a job while going to school.

One study showed pre-college adoles­cents rated "divorce of parents" and "wrecking the family car" as most stressful. Those events are stressful for other age groups as well.

What are major stressors for college students?

A common stressor for people of all ages is moving to a new location. Clinical psychologist Ronald Raymond, who worked for a relocation counseling firm, found evidence of great stress associated with moves.

Of 2,000 people studied, only 30% did it without "anguish." Fear and a sense of isolation take over upon arrival at a new town, and this can paralyze people right when they should be making new friends. Fearing rejection, many rationalize that the new community is unfriendly (Brooks, 1983)

Raymond found that the worst time, for people who moved, was about two months after arriving at the new com­munity. At that point the honeymoon period of excitement over new oppor­tunities was over.

Culture shock can set in. Unfamiliar streets, foods, and social rituals can become disturbing symbols of strangeness.

The best medicine, Raymond said, was preventative. One should become in­volved with others in the new community immediately upon arrival, during the honeymoon period, when it is easiest.

What is evidence that moving can be stressful? What did a psychologist recommend, to minimize this effect?

Getting fired is notoriously stressful. (In Chapter 9 it was described as one of the few things, along with death of a spouse, that could cause a lasting decline in a person's normal happiness level.)

However, being employed is no guaran­tee against stress. Certain occupations are known to be high-stress jobs. These include being an air-traffic controller, member of the police force, or an executive.

The helping professions like social work, counseling, and clinical psychology are quite stressful. They are associated with a high rate of burn-out. Professions where workers constantly face deadlines, such as printing and publishing, are notorious for high alcoholism rates that presumably reflect stress.

MacLennan and Maier (1983) empha­sized that stress is increased by lack of control. They wrote:

We found that rats exposed to footshock became sensitized to both amphetamine and cocaine only if they cannot cope with or control the shock. (MacLennan and Maier, 1983, p.1091)

In this case, it is not the stressful stimulus (stressor) that causes stress: it was lack of control that caused stress. Rats who were allowed to cope with footshock by running from one compartment to another did not show sensitization.

(Sensitization was in this case a mea­sure of stress. Normally sensitization to amphetamines would be caused by giving the rat a dose of amphetamine. In this case stress had the same effect.)

What factor increased stress, in laboratory studies?

In the MacLennan and Maier study, groups of rats were in yoked pairs. Each rat received shocks at the same time as the rat it was paired with, but only one had control (being able to run to a different compartment and escape). The rats without control were the ones that showed bad effects of stress.

To some psychologists, that seemed very significant. Ideas like effectence and learned optimism, emphasizing the importance of feeling in control of one's destiny, came out of this type of research.

Animal studies show the effects of stress on immune competence: the disease-fighting capability of the body.

"...Stress-induced increases in corticoid hormones produce secondary effects involving T cells, B cells (bursa equivalent), NK (natural killer) cells, and thymic components, all vital elements of the immuno­logical apparatus." (Riley, 1981, p.1101)

In one study, Visintainer, Volpicelli and Seligman (1982) showed that rats given inescapable shock were less likely to reject tumors. Rats who were able to control the shock showed no such effect, even though they received as many jolts as the helpless group.

What variable influenced the effect of footshock on immune response?

The finding that control influenced stress, and stress influenced immune function, implied that immune function was influenced by psychological factors. That led to a new discipline: psycho­neuro­immunology (PNI).

How was stress important to the discipline of PNI?

PNI started with great hopes in the mid-1990s. Researchers sought psychological influences on the immune system. Psycho­neuroimmunology still exists; the PsychoNeuro­Immunology Research Society publishes a journal devoted to it.

However, attention to PNI as such has waned. Many proposed influences on immune function were studied, and few produced effects.

Looking back, almost all the research showing reliable psychological effects on health involved one variable: stress. To this day, most PNI research involves stress, cytokines, and inflam­mation, and how they interact with various disorders.

Cognitive Effects of Stress

The excitation caused by stress makes complex and subtle thought processes more difficult. There is too much noise in the nervous system. This leads to phenomena such as "freezing" (being unable to think straight or remember important information) on an exam.

Under stress, a person becomes more reactive and impulsive and more likely to do something maladaptive. A psych­ologist gave the example of a friend who, after being fired, spent 10 hours a day playing pinball for two weeks.

What are negative effects of stress? What activities are performed well under stress?

One type of cognitive and motor activity can be performed well under stress: the type psychologists call overlearned. Overlearned activities are things repeat­ed so many times they become auto­matic, or nearly so: things you "could do in your sleep." Those actions can be performed well in stressful situations.

Most academic material is not overlearn­ least, not until you are a teacher who has given the same lecture many times. The more superficially something is learned, the more likely it is to become unavailable to memory in an emergency.

Why is it important to keep emergency procedures simple?

This is why emergency procedures must be kept simple. In an emergency, people are under unusual degrees of stress.

If they have to remember a complex procedure, they may fail entirely. The 911 system for getting emergency help, used in American cities, works well because people can remember to dial 911 even if they are panic-stricken. Stories of people freezing at the telephone because they cannot find "eleven" on the dial are untrue (Brunvand, 1984).

How does mild stress benefit students?

As mentioned in Chapter 6 (Memory) and Chapter 9 (Motivation) mild stress can actually help make behaviors easier. Chapter 6 discussed how a small amount of adrenaline, perhaps the amount stimulated by a caffeine drink or an impending test, increases the brain's ability to form new memories.

Chapter 9 discussed how mild stress makes actions of all kinds more likely. (It compared the effect of a gentle tail pinch, a mild stressor for a rat, to the Hullian concept of drive, an all-purpose energizing force.)

An impending deadline may suddenly unleash a student's ability to write a term paper, after weeks of procrastination. Severe stress can immobilize people, but mild stress has an activating effect.


Antelman, S. M., Eichler, A. J., Black, C. A., & Kocan, D. (1980). Interchangeability of stress and amphetamine in sensitization. Science, 207, 329-331.

Axelrod, J. & Reisine, T. D. (1984). Stress hormones: Their interaction and regulation. Science, 224, 452-459.

Brooks, A. (1983, October 17). Common trauma of moving. New York Times, p.18.

Brunvand, J. H. (1984) The Choking Doberman. New York: Norton.

Kiecolt-Glaser, J. K., Page, G. G., Marucha, P. T., MacCallum, R. C., & Glaser, R. (1998). Psychological influences on surgical recovery: Perspectives from psycho­neuroimmunology. American Psychologist, 53, 1209-1218.

MacLennan, A. J. & Maier, S. F. (1983). Coping and the stress-induced potentiation of stimulant stereotypy in the rat. Science, 219, 1091-1093.

Riley, V. (1981). Psychoneuroendocrine influences on immunocompetence and neoplasia. Science, 212, 1100.

Visintainer, M. A., Volpicelli, J. R., & Seligman, M. E. P. (1982). Tumor rejection in rats after inescapable shock. Science, 216, 437-439.

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