ONE WEDNESDAY MORNING an engineer named Marcus was called into his boss's office. The manager thanked Marcus for his 30 years of service to the firm and handed him his pink slip. A security officer escorted Marcus back to his office to clean out his desk and then to the building's exit. The same thing happened to 100 other engineers that day—the Dallas computer company they worked for laid them off without any notice and sent them on their way.

Psychologist James W. Pennebaker, then at Southern Methodist University, managed to recruit more than half of these men and women to take part in a simple experiment several months after they had been let go. “I have never worked with such a bitter and hostile group of research subjects,” remembers Pennebaker, now at the University of Texas at Austin. He asked everyone to spend 20 minutes a day for five consecutive days writing in a diary. Some members of the group were instructed to note how they spent their time each day; a second group was asked to write down their deepest feelings about the loss of their job; and the remaining volunteers were given no writing instruction at all.

The people who ended up in the second group—those who poured out their anger and disappointment onto paper—subsequently experienced a dramatic advantage over their peers in gaining new employment. More than a quarter of them found a new job after three months. Among the other groups, a much smaller percentage found work, even though all the participants expended the same amount of effort in their job hunt and got about the same number of interviews. The results were so striking that Pennebaker and his colleagues terminated the experiment early so they could advise everyone to start writing about their innermost feelings immediately.

That was 1994. Since then, dozens of studies have shown that “expressive writing” can heal the body and soul. In the months after an exercise such as the one in Pennebaker's study, most people—whether they are students, sex criminals or sick patients—feel significantly better, physically and mentally. According to an evaluation of 13 different studies on healthy subjects, the results are at least as beneficial as psychological intervention. And more recent research shows that expressive writing has a long-term favorable influence on the immune system and blood pressure.

The Right Way to Write

Whereas all these findings seem to indicate that picking up a pen is a cure-all for our troubles, it is not quite so simple. It is important to choose the right topics. Researchers agree that positive effects from writing are achieved only when people deal with a negative situation—specifically, a situation that has been bothering them and that they have not been willing to discuss with anyone. And Pennebaker warns that the moment of writing itself can be painful. “I often saw our subjects crying,” he says. But releasing blocked emotions—Sigmund Freud called this catharsis—leads, at least in the long run, to healing.

In addition, describing a problem or retelling an experience, rather than merely pondering it, can bring about a change of perspective. In 2006 Sonja Lyubomirsky of the University of California, Riverside, enlisted 96 of her students to evaluate all three of these methods. Only the first two proved therapeutic. Telling stories, whether in writing or out loud, enabled subjects to analyze an event step by step; it provided a beginning and an ending. Merely thinking about it, on the other hand, created chaos: events, images and emotions became intertwined, leading people to relive the experience—with the danger of becoming lost in misery all over again.

Those who profit the most from expressive writing, Pennebaker says, neither skirt the difficult issues nor attempt to minimize them. Sometimes individuals are also able to discover some meaning in their traumatic experiences—but this is just an added bonus, unnecessary for therapeutic benefit. Writers should never force themselves to try to find hidden meaning in their suffering. That could do more harm than good.

To make the most of a writing session, Pennebaker advises people to focus on three questions: What happened? How did I feel about that? Why did I feel that way? And the first commandment is always to feel free: don't worry about grammar, spelling, complete sentences or repetition. None of that matters. According to Pennebaker, “What counts is that you devote at least 15 minutes and delve into your deepest feelings.”

But be careful when dealing with positive experiences. Writing about good memories has the opposite effect. In Lyubomirsky's study, when students were asked to produce written analyses of their happiest moments, they actually damaged their positive feelings. Perhaps because writing created a psychological distance from these memories, the students' satisfaction with them ebbed in the weeks that followed. On the other hand, it was useful to indulge in thinking about these happy experiences. Interestingly, short written notes do no harm: in a 2003 study by Robert Emmons of the University of California, Davis, 65 students jotted down five things every week that they were thankful for. The participants blossomed during the experiment, experiencing good moods more often and interacting with their peers in positive ways.

Now, more than a decade after expressive writing helped Pennebaker's frustrated computer engineers find jobs, a growing body of research points to a common and welcome conclusion: no one has to labor for hours over a diary to see positive changes in his or her well-being. Fifteen minutes now and then is plenty—if you are doing it right.