Introduction:
The associations between depression and cigarette dependence had been established through a large amount of studies. Nevertheless, mechanisms underlying such association are not clearly recognized. The main aim of this study was to explore whether the perception of environmental reinforcement mediates the effect of cigarette dependence on depressive symptoms in smokers seeking smoking cessation treatment.

Methods:
The sample consisted of 275 smokers (61.5% women, average age 45.36 years, SD = 10.96), seeking smoking cessation treatment in the Smoking Cessation and Addictive Disorders Unit of the University of Santiago de Compostela. The following questionnaires were applied: Fagerström Test of Cigarette Dependence (FTCD), Beck Depression Inventory - II (BDI-II) and Environmental Reward Observation Scale (EROS) that evaluates the degree of reward / reinforcement provided by the environment. To examine the associations between study variables bivariate correlations were tested. Mediation analyses were conducted through the statistical macro PROCESS.

Results:
The total sample obtained an average score in the EROS of 27.92 (SD = 4.51), in the FTCD of 4.78 (SD = 2.16); and in the BDI-II of 10.57 (SD = 9.17). Bivariate correlations were statistically significant between depressive symptoms, perceived environmental reinforcement and cigarette dependence. There was a significant direct effect of cigarette dependence on depressive symptoms (b = 0.63; p = .004), and a significant indirect effect of cigarette dependence on depressive symptoms via perceived environmental reinforcement (a*b = 0.36, 95% CI [0.140 − 0.612]).

Conclusions:
Findings show significant associations between cigarette dependence and depressive symptoms through perceived environmental reward in smokers seeking smoking cessation treatment. This support previous research suggesting that smoking cessation interventions including components aimed at increasing reward probability and access to reward stimuli or activities others than tobacco, could be useful in order to improve depressive symptoms, as these could be a barrier to achieve smoking abstinence.

Funding:
This research was supported by the Spanish Ministry of Economy and Competitiveness (Project reference: PSI2015-66755-R) and co-financed by FEDER (European Regional Development Fund; pluri-annual plan 2014-2020).