By Emily Reynolds

Emotions have a powerful part to play in both our behavioural choices and our health. Experiencing a range of positive emotions has been associated with lower levels of inflammation, for example, and emotional control has even been linked to higher performance in sportspeople. Negative emotions, too, can have a serious impact on behaviour: research has investigated the emotional triggers of self-harm, for instance.

Now new research from Charles Dorison and colleagues at Harvard University, published in PNAS, has looked at the role of negative emotions in addiction. Though some theories say negative mood in general is associated with problematic substance use, the study suggests that, for tobacco at least, it’s sadness per se that is related to addiction.

For their first study, the team looked at data from a national survey that tracked 10,685 people over 20 years. It found that sadness significantly predicted smoking status — something that no other emotion, positive or negative, did. There seemed to be a long-term effect, too: sadness reported at the first phase of the data predicted smoking ten and twenty years later.

In the second study, which looked at cravings for cigarettes, 425 smokers were placed into three conditions: sadness, disgust and neutral. Those in the sadness condition were shown a clip from the notoriously tear-jerking Pixar film Up, and were then asked to write about a time they themselves had experienced significant loss, like the elderly man in the film.

Participants in the disgust condition were shown another iconic film clip: the scene from Trainspotting in which Ewan McGregor roots around in a decidedly unclean toilet. They were then asked to write about an unsanitary experience in their own life. And in the neutral condition, participants viewed a video about furniture making and were asked to write about their work.

Before and after watching the clips, participants were asked three questions about how much they were craving cigarettes — and, once again, sadness was related to tobacco use. Sadness increased craving compared to both the neutral and disgusted states, the latter of which appeared to decrease cravings (perhaps rather unsurprisingly, although the effect wasn’t statistically significant).

A third study again looked at cravings, asking 760 participants to watch either neutral or sad videos, and then indicate whether they’d prefer to have a few puffs of a cigarette immediately, or wait to have more puffs after a small delay. Those in the sadness condition were far more impatient, craving fewer puffs sooner than those in the neutral condition.

And in a final study, 158 smokers were asked to abstain from smoking for at least eight hours, with their breath verified through a carbon monoxide test. Participants were again asked to watch either a sad or neutral video. They then smoked a cigarette through a device that measures volume, speed and duration of puffs. Mirroring previous results, smokers in the sadness condition were both more impatient and smoked more per puff.

Though the findings certainly do present a strong argument for an emotion-specific model for smoking cessation, there were things left unaddressed. Only one of the experimental studies looked at other negative emotions (i.e. disgust, induced by watching the Trainspotting clip). Concluding that sadness is more potent than other negative emotional states may be too strong a statement — we have no idea how anxiety, fear or anger, for example, could trigger tobacco use.

It may also be worth conducting further research on the link between negative emotions and other addictive substances: the relationship between sadness and heroin use, for example, may be entirely different.

But encouraging people to give up smoking is not an insignificant health intervention: in both the US and the UK, tobacco use is the leading cause of preventable death, and one billion more premature deaths worldwide are expected to occur because of smoking by the end of the century. Understanding that, for many, smoking is not just habit-based but is deeply entwined with emotions may be a good way to develop anti-smoking programmes that work for everyone.

– Sadness, but not all negative emotions, heightens addictive substance use

Emily Reynolds (@rey_z) is a staff writer at BPS Research Digest