10 Things Every Man Should Know about a Woman's Brain

Affecting up to 80 percent of women, PMS is a familiar scapegoat. But women are affected by their cycles every day of the month. Hormone levels are constantly changing in a woman's brain and body, changing her outlook, energy and sensitivity along with them.

About 10 days after the onset of menstruation, right before ovulation, women often feel sassier, Brizendine told LiveScience. Unconsciously, they dress sexier as surges in estrogen and testosterone prompt them to look for sexual opportunities during this particularly fertile period.

A week later, there is a rise in progesterone, the hormone that mimics valium, making women "feel like cuddling up with a hot cup of tea and a good book," Brizendine said. The following week, progesterone withdrawal can make women weepy and easily irritated. "We call it crying over dog commercials crying," Brizendine said.

For most women, their mood reaches its worst 12-24 hours before their period starts. "It is not entirely an issue of free will," Brizendine stressed.