['Young adulthood represents a period of continued smoking progression and the establishment of regular and long-term smoking practices. Our understanding of the psychological processes that facilitate and solidify regular smoking patterns in this developmental period is limited. We sought to evaluate the role of depression symptoms in young adult smoking uptake and to evaluate whether non-smoking related alternative reinforcers was a mechanism by which depression symptoms influence smoking.', 'The sample was composed of 834 young adults who participated in a longitudinal study of smoking adoption (aged 18-22 years).', 'In this prospective cohort study, smoking, depression, alternative reinforcers and several covariates were measured annually via telephone from emerging adulthood (age 18) to young adulthood (age 22).', 'Results of a parallel processes latent growth curve model showed that depression symptoms level (baseline age 18) had a significant negative effect on substitute alternative reinforcers trend (β\u2003= -0.01, Z\u2003= -3.17, P=0.002) and that substitute reinforcers trend had a significant negative effect on smoking trend (β\u2003=\u2003-0.62, Z\u2003=\u2003-2.99, P\u2003=\u20030.003). An assessment of indirect effects revealed that depression symptoms level had a significant positive indirect effect on smoking trend through substitute alternative reinforcers trend (β\u2003=\u20030.01, Z\u2003=\u20032.09, P\u2003=\u20030.04, 99% CI\u2003=\u20030.001, 0.02), such that greater depression symptoms at baseline predicted decreases in substitute reinforcers across time which in turn predicted increases in smoking uptake/rate from emerging to young adulthood.'] Do declining alternative reinforcers link depression to young adult smoking?