Background: Dopamine (DA) system dysfunction is implicated in the pathophysiology of major depressive disorder (MDD). We sought to determine if cigarette smokers with a history of MDD and current mild depressive symptoms have abnormal smoking-induced DA release (measured indirectly as change in (11)C-raclopride binding potential [BP(ND)]).
Methods: Fifty-six cigarette smokers either with (n = 10) or without (n = 46) a history of MDD (MDD+ and MDD-, respectively) underwent bolus-plus-continuous-infusion (11)C-raclopride positron emission tomography, during which they smoked a regular cigarette. Presmoking to postsmoking changes in (11)C-raclopride BP(ND) were compared between groups. Also, correlations were determined between change in BP(ND) and depression, anxiety, and withdrawal rating scale scores for the MDD+ group.
Results: The MDD+ group had a significantly greater reduction in (11)C-raclopride BP(ND) (-16.3%) than the MDD- group (-8.4%) (analysis of covariance [ANCOVA], p = .03). Significant negative correlations were found between depression/anxiety and change in (11)C-raclopride BP(ND) (r = -.77, p < .01 and r = -.74, p = .01, respectively).
Conclusions: MDD+ smokers have greater smoking-induced DA release than MDD- smokers, and higher depression/anxiety levels are associated with greater smoking-induced DA release. These findings support the theory that MDD+ smokers have DA system dysfunction, including heightened smoking-induced DA release.