The menstrual cycle appears to have an effect on nicotine cravings, according to a new study. "Our data reveal that incontrollable urges to smoke are stronger at the beginning of the follicular phase that begins after menstruation. Hormonal decreases of estrogen and progesterone possibly deepen the withdrawal syndrome and increase activity of neural circuits associated with craving," an investigator said, suggesting that it could therefore be easier for women to overcome abstinence-related withdrawal symptoms during the mid-luteal phrase, i.e. after ovulation, when their levels of estrogen and progesterone are elevated.