We're all aware that smoking kills. But what's less well known is that when compared to men, women get hooked on cigarettes more quickly, have more trouble quitting and experience worse withdrawal symptoms.
Why is it that women face more problems ditching cigarettes than men? According to recent science, it might have something to do with when they try.
Studies suggest menstrual cycles and the accompanying hormonal fluctuations may make it physiologically harder to quit at certain times of the month. This means that women hoping to give up smoking battle biological forces that men don't. But there's also some good news: Women who want to renounce cigarettes for good may be able to target specific windows during their menstrual cycle when the task will be easier — or even get on birth control pills that will help them break the habit.
The science: Scientists who study addiction behavior generally accept that women have more trouble than men quitting smoking. With this in mind, researchers studied whether menstrual cycle fluctuations in two key female hormones, progesterone and estrogen, might be part of the equation.
There are three main phases in the menstrual cycle: menstruation, the follicular phase and the luteal phase. Menstruation kicks off the cycle. After shedding your endometrial lining for about three to seven days, you move into the follicular phase — about five days of preparing for ovulation (peak fertility). The luteal phase, sometimes called the premenstrual phase, starts on the day you ovulate and lasts about two weeks. Then it's back to your period.
Levels of both "key" female hormones, progesterone and estrogen, drop during the follicular phase and peak during the luteal phase.
Image Credit: Chris 73 via Wikimedia Commons
In one study, which will soon be published in the journal Nicotine & Tobacco Research, University of South Carolina researchers recruited current female smokers (at least 10 cigarettes per day) who were interested in quitting and willing to take medication to help them. They were also "freely cycling," meaning they weren't taking hormone replacement therapy, birth control pills or any other form of hormonal contraception. Participants charted their cycles based on ovulation kits. High progesterone levels, researchers found, corresponded to more success abstaining from cigarettes.
Male smokers were included in a different study in which researchers examined how and when women respond to two different things that make smokers relapse: negative emotional feelings and external smoking cues, (e.g., cigarette advertisements) and social situations where people are smoking. Women had stronger cravings, scientists found, in response to smoking cues during one phase and emotional stress during a different phase.
What this means for women: Firstly, it might be easiest for women to quit smoking and avoid relapsing during the luteal phase of their menstrual cycles, when progesterone levels are highest. But this finding, still only prospective, needs to be tested through clinical trials for birth control pills that work by controlling progesterone levels. The researchers believes there may be an outcome where birth control pills help prevent previous smokers from relapsing.
"We haven't done lab or clinical work administering progesterone," Kevin Gray, a psychiatrist on the research team, told Mic, "but I do see that as a potential place to go. Wouldn't it be nice if a hormonal contraceptive was a way to kill two birds with one stone?"
Secondly, there may be a relationship between hormone levels and the kind of trigger that makes female smokers relapse. During one phase of their cycle, women may be most likely to give in to temptation when their emotions get the best of them. During another phase, however, women might stay strong through stress but break down when advertisements or other people remind them of the joys of smoking.
"We tried to untangle stress cues from smoking cues and have found it interesting that there seems to be an association at opposite ends of the menstrual cycle with different kinds of cue reactivity," Gray said. "So when we talk about when during the menstrual cycle cravings are more or less manageable, it may come down to which [types of cues] induce the craving."
Journalist Edward Murrow lights a cigarette for Marilyn Monroe, whose smoking habit was well-known. Image Credit: Getty Images.
There's still more to learn: At the University of Montreal, neuroscientists are similarly looking at cigarette cravings between sexes and across the menstrual cycle. But, in addition to examining the role of hormonal fluctuations, researchers are studying brain activity too. In a recent study published in Psychiatry Journal, a research team compared self-reported cravings and neural activity between male and female smokers during two phases of female participants' menstrual cycle.
Based on fMRI (functional magnetic resonance imaging), activation of brain regions did not significantly differ between men and women, said lead researcher Adrianna Mendrek. But female participants did exhibit stronger regional neural activity during one phase of their period (the follicular).
Mendrek's team came to similar, though murkier, conclusions as the South Carolina researchers: The luteal phase may be an easier time to stop smoking. But unlike the South Carolina team, Mendrek believes that estrogen may play a more critical role than progesterone. So while the teams have come to similar conclusions, it seems that more work needs to be done to identify the precise cause.
The biological component of smoking is one piece of a puzzle riddled with complications, including environmental factors, like stress and peer pressure, and individual differences between women's responses to hormonal fluctuations. Though researchers are still trying to pin down biological underpinnings, they are confident that, when it comes to smoking addiction, sex matters.
"I see this as a health disparity [between women and men] that's important to address," said Gray, who explained that most smokers relapse in the long term. "At the very least, I'd like to see a female smoker who wants to quit as having the same chance of success that a man does."
GE Scientists and Mic are partnering to share the latest advances in brain research and technology through BrainMic, a Spotlight Series that explores the universe in our heads, now through December 2014. Click here to read more from this series on BrainMic >>