Ask a smoker what they get out of cigarettes and they are likely to talk about pleasure, contentment, and an overall good feeling. Nicotine, the active ingredient in cigarettes, is a stimulant. Used in low doses like those delivered by combustible cigarettes, stimulants activate the nervous system, resulting in enhanced arousal and alertness. Nicotine binding in the limbic system — the part of the brain that houses the pleasure and reward center — releases dopamine, resulting in feelings of euphoria. These effects combine to give smokers a boost in their mood.

In this context, research from a team at Harvard University, that found that when smokers feel sad they reach for cigarettes and inhale longer and deeper, is not surprising. Cigarettes are a “solution” to the “problem” of sadness that smokers seem to learn to use effectively. This new research is the first to show that sadness elicits nicotine use much more than other negative emotions, and that sad feelings are not only associated with smoking, but can actually cause it.

Smoking may blunt an adaptive and necessary emotion

Sadness is a basic emotion, typically felt in response to loss. The experience of sadness and the underlying neurobiology is universal. Sadness that is too intense or too prolonged — i.e., depression — is a disorder that results in dysfunction. But normal sadness has an adaptive function: people experiencing sadness focus their attention internally and become better problem solvers.

The expression of sadness is physiologically determined. Humans can reliably read sadness on each other’s faces independent from cultural cues, and these signals provoke empathy from others — another benefit to the individual who is sad. In this regard sadness, while unpleasant, has its upsides; its universality is an indication of its survival advantage.

While smokers get immediate relief from sadness with a cigarette, that may come at a cost if they also lose these adaptive benefits. “Treatment” of sad emotional states with nicotine over time may also impair innate restorative responses, just as treatment of chronic pain with opioids results in many patients experiencing hyperalgesia, a pathologically heightened response to painful stimuli. Indeed, this may help to explain the association between smoking and depression.

Part of maturing is learning to manage emotions

Compared with adults, adolescents experience emotions more strongly; with maturity they transition from the emotional reactivity typical of this age group to the more tempered presentation of adults. When it comes to sadness, reactivity and response are age-dependent: the triggering content of sadness is less tightly coupled with physiologic responses in the young compared to mature adults. Experience appears to be a crucial component of the maturational process.

What happens when adolescents use nicotine to blunt their sadness?

Does smoking interrupt emotional maturation, making young smokers susceptible to depression? Does disruption in emotional maturity make adolescent smokers more likely to use other drugs? The short answer to all of these questions is that we do not know, but there is reason to be concerned, because we do know that smoking is associated with increased risk of depression, marijuana use, binge drinking and use of other drugs including opioids. Since most smokers start using cigarettes during their teen years, these questions have real salience.

After 20 years of dramatic decline in the rates of smoking among high school students, and a more gradual decline among adults, e-cigarettes and vaping devices have begun to reverse these trends. The new findings demonstrating the linkage between sadness and smoking should give us all pause. While the health impacts of smoking have been well documented over the past 50 years, we are still learning about the impacts of nicotine.