Smoking trajectories from adolescence to early adulthood as a longitudinal predictor of mental health in adulthood: evidence from 21 years of a nationally representative cohort.

Continued smoking, especially early-onset and heavy smoking from adolescence to young adulthood, appears to increase the risk of poor mental health later in mid-adulthood, and quitting smoking in young adulthood may mitigate such risk even among early-onset smokers. Mediation analyses underscore the role of using multiple substances in this pathway.