Michael J Rohrbaugh and Varda Shoham, of the University of Arizona, say that close relationships can perpetuate individual health problems because one person’s behaviour can set the stage for what another does.

The researchers say that smoking can promote emotional connection for couples when both partners smoke and preserve stability in their relationships, which also explains why some people would not kick the butt.

Describing their study in the journal Family Process, the researchers revealed that they had 25 couples discuss a health-related disagreement before and during a period of actual smoking, then use joysticks to rate how they had felt from moment to moment (from very positive to very negative) while watching themselves on video.

While one partner in each couple smoked despite having a heart or lung problem, both partners in some couples were smokers.

The joy-stick ratings of partners in dual-smoker couples became more positive and more synchronous contingent upon lighting up – as if they were dancing to the same emotional tune.

However, single-smoker couples reported decreased positive emotions, and less affective synchrony.

While it is believed that health-compromising habits like smoking is purely an individual matter of motivation or addiction, the results of the new study suggest that social factors beyond the smoker are important as well.

The researchers say that having a smoking partner may make a huge difference in how smoking fits the couple’s relationship, which in turn has implications for helping one or both partners quit.