The self-control that allows people in recovery to maintain abstinence requires a measurable expenditure of mental energy, reserves of which are not inexhaustible, according to researcher Roy Baumeister of the Center for Advanced Study in Behavioral Sciences in Stamford, Calif.

In a series of experiments, Baumeister demonstrated that exercising willpower requires mental energy, and said that exercising willpower can be impeded by other factors that deplete energy reserves, such as physical exertion or stress.

From a treatment perspective, the findings may argue against asking patients to tackle too many problems at once, such as quitting smoking at the same time they are trying to kick heroin or alcohol.

"When energy is depleted ... it's much harder to be good," said Baumeister. "By understanding that will depends upon energy, it sheds light on the way in which people grapple with alcohol and drug abuse and how we regulate ourselves."

To show how willpower is related to emotional control, Baumeister had three groups of study subjects perform repeated hand-grip exercises before and after watching a movie about a nuclear holocaust. The first group was told to actively suppress their emotions during the film; a second group was told to "feel" as much as possible, while a third group was given no specific instructions.

Baumeister found that the group that was given free rein to express their emotions during the film performed nearly the same number of hand-grip exercises before and after the film, while those who were told to suppress their emotions did an average of 25 fewer repetitions after the film. (The neutral group did about 18 fewer repetitions.) "Trying to regulate their emotions took something out of them, and hurt their stamina and willpower," Baumeister concluded.

In a second test, Baumeister instructing a study group to suppress a mental image of a white bear while working to solve a series of (unbeknownst to them) unsolvable anagrams. Researchers found that the suppression group worked at the task for an average of 563 seconds before giving up, while a group that was allowed to think about the bear worked for 867 seconds, and a control group worked for 758 seconds. "Suppressing used up resources again," said Baumeister.

Turning to a self-control experiment that Baumeister described as "a bit meaner than the others," researchers instructed a group of volunteers to skip lunch, then put them in a room filled with the aroma of fresh-baked chocolate-chip cookies. On the table was a plate of tempting cookies and a bowl of radishes.

One group was left in the room with the instruction that since they were in the "radish group," they could not eat the cookies. "There were a lot of close calls, but nobody actually bit into the forbidden fruit," reported Baumeister.

Next, the group was taken to another room and given an impossible task to work on. The "radish group" stuck to the task for just 8 minutes on average, while a second group that was allowed to eat the cookies worked for 20 minutes, and a control group worked for 18 minutes before giving up. Baumeister's conclusion: suppressing desire also drains willpower.

But is it the act of suppressing emotion, thought-processes, and desire that drains willpower reserves? Perhaps not, said Baumeister, pointing to further experiments that showed that people given a choice of making a speech either in agreement or opposed to their own beliefs performed a task more poorly than those asked to prepare a counterattitudinal speech. "It's making the choice that depletes resources, not the behavior," Baumeister concluded.

Baumeister presented his findings during the annual meeting of the Research Society on Alcoholism, held June 28 to July 3 in San Francisco, Calif.