Women who resolved to quit smoking in 2015 may find greater success by timing their plan with their period, research published Sunday in Psychiatry Journal suggests. 

Researchers at the University of Montreal found that women’s urge to smoke is strongest immediately after menstruation, a stage called the follicular phase. Hormonal decreases of estrogen and progesterone exacerbated withdrawal symptoms and increased neural activity related to cravings, the study authors hypothesized. Nicotine cravings were lowest after ovulation— called the mid-luteal stage— when hormone levels are elevated.

According to a news release, the goal of the study was twofold: to study gender differences in neuronal circuits linked to craving, and to determine whether brain changes linked to nicotine withdrawal change in tandem with these hormone levels.

Thirty-four men and women who each smoke more than 15 cigarettes a day completed questionnaires, and underwent MRI brain scans while looking at neutral pictures and others designed to make them want to smoke. Study authors scanned women at the beginning of the follicular phase and the mid-luteal phase of their period, and they measured men and women's hormone levels. 

Activation patterns of neuronal circuits among men and women varied considerably during women’s menstrual cycle: There was more activity during their follicular phase and less activity during the luteal phase.

The researchers’ conclusions are consistent with findings from previous animal studies, which suggests that women who smoke have a harder time quitting than men, even when they smoke the same amount.  

"Female rats become addicted more quickly and are willing to work harder for the same quantity of dose," lead study author Adrianna Mendrek, a psychology professor at the University of Montreal and its affiliated Institut universitaire en santé mentale de Montréal, said in the news release. Her team’s new findings explain why.

"A greater knowledge of the neurobiological mechanisms governing addiction should enable us to better target treatment according to the smokers profile," Mendrek noted.