Adults who smoke tobacco tend to have higher levels of the stress hormone cortisol and spend more time awake during the night after initially falling asleep, compared to adults who do not smoke.

In people who smoke, higher levels of the stress hormone cortisol are linked to spending less time awake after falling asleep, suggesting cortisol may reduce sleep disruptions caused by smoking, though how this happens is not understood.

People who smoke report sleeping just as well as non-smokers, even though objective measurements show their sleep is more disrupted with more time spent awake during the night.