A new way to image people's brains while they smoke has revealed physical evidence for a phenomenon scientists have studied for quite some time: Cigarettes have different effects on men than they do on women. Now, researchers believe the differences could one day lead to gender-specific treatments to help people quit.
Researchers from Yale University used positron emission tomography (PET) scans to capture the changing levels of a neurotransmitter called dopamine, a chemical in the brain that plays a role in the brain's pleasure and reward pathways. In addition to reinforcing good-for-you behaviors by activating reward pathways in the brain, dopamine levels also increase when addictive substances like nicotine enter the body.
Using the PET scans, the researchers were able to make "dopamine activation movies" that would reveal how fast the release of dopamine occurred, and where it occurred in different parts of the brain. Before this breakthrough, scientists had not been able to accurately image a smoker's brain during the act of smoking, as the brain's response to nicotine is relatively rapid and short-lived.
For the study, published earlier this month in the Journal of Neuroscience, lead author Kelly Cosgrove, Ph.D., of Yale University, recruited 16 addicted cigarette smokers. The eight men had smoked cigarettes for an average of at least 19 years, and the eight women had smoked cigarettes for an average of at least 17 years. They were instructed not to take any nicotine replacement therapy or medication during the study.
Cosgrove told each participant to smoke one to two cigarettes of their own choosing, at their own pace. She scanned their brains both before, during and after their smoking sessions and created movies out of the assembled images.
In men, a part of the brain called the ventral striatum showed significantly more rapid and consistent dopamine activation when they were smoking as compared to women, who showed mild activation, if at all, and no consistency when it came to the speed of the activation. Women, on the other hand, showed significantly more dopamine activation -- and fast activation -- in the right dorsal putamen, whereas men showed only low or moderate activation in this area of the brain.
The results suggest that, neurobiologically, men are more responsive to the nicotine in a cigarette, while women tend to be rewarded more by the "cues" of smoking, like the smell and taste of the smoke. If borne out in larger studies, Cosgrove's findings could have implications for future, gender-specific treatment to help people quit smoking. But they may also explain why current cessation tools, like nicotine patches, seem to be more effective in men than in women. In men, a patch may provide all the nicotine that's needed to satisfy a male smoker's craving, while female smokers may miss the taste or smell of a cigarette if they're using just a patch.
Cosgrove cautioned that her results don't mean that female smokers are less dependent on nicotine than male smokers.
"I think it confirms that strategies that focus on drug reward are likely to work better for men –- these would include the nicotine replacement strategies [like the patch]," Cosgrove wrote in an email to HuffPost. "And, for women it highlights that we need different and new medications -– ones that target the reasons why women smoke, such as to relieve stress and manage mood."
Kenneth Perkins, a psychiatry professor at the University of Pittsburgh, speculates that two tools -- e-cigarettes and low-nicotine cigarettes -- might be novel ways to help women wean themselves off the more harmful cigarettes if the standard cessation treatment (say, prescription drugs, plus counseling) doesn't seem to be working. However, research hasn't borne this out yet, and it's "too soon" to know, he said.
"If [women] are smoking more for the taste and sensory effects, then low-nicotine cigarettes might be an effective way to wean themselves off the regular cigarettes, whereas men might have more nicotine withdrawal and not really get much out of those [low-nicotine] cigarettes," said Perkins. "The possibility is that they might be a more effective way for women to quit than men, but that's purely speculative at this point."
Perkins has also conducted lab studies comparing acute responses to smoking in men and women. Perkins found Cosgrove's investigation interesting because they seem to support, with brain imaging, what Perkins has observed with behavioral experiments or self-reported participant responses.
"On average, women seem more responsive to the sensory effect of smoking, like the taste and smell of smoke, whereas men seemed to be more sensitive to the nicotine content itself," said Perkins about his own research. But he cautioned that while the difference is "significant," men and women still have "more overlap than there is difference" when it comes to cigarette addiction.
Cigarette addiction causes one in five deaths in the U.S. and is also the country's leading preventable cause of death. For every one smoking-related death, there are 30 more people who are suffering from a tobacco-related illness, according to the Centers for Disease Control and Prevention.