Free Willpower by Roy F. Baumeister Page A

cycle only if she wasn’t impregnated during the earlier ovulation phase, have speculated that natural selection favored women who became dissatisfied with infertile men, thereby liberating themselves to seek another mate. That hypothesis certainly jibes with another name that women give to PMS: Pack My Stuff. But it’s not clear that the evolutionary benefits would have outweighed the costs, or that such selective pressures even operated on the ancient savanna. For our hunter-gatherer ancestors, PMS was presumably less of a problem because women spent more of their lives either being pregnant or breast-feeding children.
    In any case, there’s now a solid physiological explanation for PMS that doesn’t involve any mysterious alien impulses. During this premenstrual part of the cycle, which is called the luteal phase, the female body starts channeling a high amount of its energy to the ovaries and to related activities, like producing extra quantities of female hormones. As more energy and glucose are diverted to the reproductive system, there’s less available for the rest of the body, which responds by craving more fuel. Chocolate and other sweets are immediately appealing because they provide instant glucose, but any kind of food can help, which is why women report more food cravings and tend to eat more. One study found that the average woman eats about 810 calories at lunch during this time, which is about 170 calories more than what she eats at lunch during the rest of the month.
    But most women still aren’t getting enough extra calories. The typical woman in a modern thin-conscious society like America does not take in enough extra food to supply the body’s increased demands for glucose during these few days each month. When there isn’t enough energy to go around, the body has to ration it, and the reproductive system takes priority, leaving less glucose available for willpower. As a general rule, women are less likely than men to suffer from lapses of self-control, but their self-control problems do worsen during the luteal phase, as studies have repeatedly shown.
    During this phase, women spend more money and make more impulsive purchases than at other times. They smoke more cigarettes. They drink more alcohol, and not just because they enjoy drinks more. The increase is especially likely for women who have a drinking problem or a family history of alcoholism. During this luteal phase, women are more liable to go on drinking binges or abuse cocaine and other drugs. PMS is not a matter of one specific behavior problem cropping up. Instead, self-control seems to fail across the board, letting all sorts of problems increase.
    One drug that isn’t used more frequently is marijuana, and that exception is revealing. Unlike cocaine and opiates, marijuana is not a drug of escape or euphoria. Marijuana merely intensifies what you’re already feeling. PMS feels bad, and a drug that intensifies the feeling isn’t going to be attractive. Moreover, marijuana doesn’t produce the same sort of addictive cravings as nicotine, alcohol, cocaine, and other drugs, so a lessening of overall self-control wouldn’t make a marijuana user more vulnerable to those kinds of temptations.
    Researchers have found that women who are prone to PMS miss twice as many days of work as other women do. Some of those missed days are due, no doubt, to the physical pain associated with PMS, but some of the absenteeism is probably related to self-control. Following rules is harder when your body is short of glucose. Inside women’s prisons, disciplinary problems based on breaking prison rules are highest among women who are at the luteal phase of their cycle. Violent, aggressive acts—legal or illegal—reach a peak among PMS sufferers during the luteal phase. To be sure, only a few women turn violent at any time, but many report emotional changes during the luteal phase. Studies have repeatedly documented increases in emotional outbursts and