This review aims to summarize neuroimaging studies in order to better understand the neural correlates of depressive symptoms in tobacco smokers. Using the keywords "depressive OR depression" AND "tobacco OR nicotine OR smok* OR cigarette" AND "neuroimage OR magnetic resonance OR smri OR structural magnetic resonance OR fmri OR functional magnetic resonance OR pet OR positron emission tomography", literature search was conducted in PubMed, Web of Science and PsycINFO databases. The first and the last author read the abstracts of all the studies found in the search (n = 179). The inclusion and exclusion criteria were applied and 150 articles were excluded. Then, both authors assessed the remaining 29 studies for eligibility and 16 studies were included in the present review. In the phase of active/chronic smoking, depressive symptoms are characterized as comorbidity related to an enhancement of dopamine release, and smokers have decreased Monoamine oxidase A (MAO-A). Stimuli-related functional magnetic resonance imaging (Stimuli-fMRI) studies also show that there is a positive correlation between the level of depressive symptoms and a greater response to general negative stimuli in active/chronic smokers. In the withdrawal phase, depressive symptoms are related to the withdrawal syndrome and increased MAO-A. Stimuli-fMRI studies show that there is a negative correlation between level of depressive symptoms and reactivity to negative stimuli in recent abstinent smokers. Major areas of the reward system such as the striatum and areas related to impulse control are activated to a greater extent in depressive smokers compared to non-depressed smokers.
Keywords: Tobacco use disorder; comorbidity; dual diagnosis; major depressive disorder; neuroimaging; nicotine dependence.