Women looking to quit smoking as a 'new year resolution' should consider timing it with their menstrual cycle.

Female smokers crave cigarettes with greater intensity than men do. They are quicker to become dependent smokers, have shorter periods of abstinence from smoking, smoke for longer periods of their life and have more difficulties quitting the habit than men. And as if women and smoking weren't complicated enough, a new study proposes that women's periods may have a significant role in their smoking habits.

A pilot study by Professor Mendrek of the University of Montreal, and its affiliated Centre de Recherche de l'Institut Universitaire en Santé Mentale, suggests that hormonal fluctuations caused by the menstrual cycle may affect craving in women.

According to the World Health Organisation, tobacco kills up to half of its users, an estimated six million people every year. The world currently has one billion smokers and it has been calculated that a person dies every six seconds due to a tobacco-related disease. The number of smokers in the Western world is decreasing, however smoking is on the rise in young women and teens.

The study included 34 healthy smokers, 19 of which were women with normal menstrual cycles. Volunteers were asked to fill out questionnaires and underwent MRI scans whilst looking at images that made them want to smoke or were neutral. Additionally, blood tests were taken before the scans in order to determine the levels of hormones progesterone and oestrogen.

Women were tested twice, once a few days after their period and again a few days before their next period. When it came to imaging craving in the brain, there was no difference between men and women as far as the neuronal circuits were concerned. However, women's pattern of activation varied over their menstrual cycle.

These preliminary findings do not provide enough evidence to suggest that menstrual cycle alone is the key factor in trying to quit smoking. Mendrek says, 'The psychosocial factors (such as stress, anxiety or depression) are much more powerful predictors of craving, difficulty quitting and relapse than hormonal fluctuations.'

Nevertheless, this study highlights the need for addressing sex in rehabilitation centres for drug addiction as the hormonal differences seen in the menstrual cycle indicate significant differences between men and women.

Mendrek believes that 'Overall women tend to become addicted faster, have higher rates of comorbidity with other mental health problems, exhibit more negative consequences of drug abuse and have more difficulties quitting than men.'

Mendrek's data emphasizes the need for gender-specific programs to quit smoking and emphasizes the need for taking the menstrual cycle into consideration when treating addiction in women.