Selective serotonin reuptake inhibitors (SSRIs) are the most widely prescribed pharmacological treatment for major depressive disorder. Despite their overall efficacy, SSRI treatment is associated with an increase in impulsive behaviors, particularly during the initial phase of treatment. Clinically, this period has been linked to elevated suicide risk, yet the behavioral and neurobiological mechanisms underlying this vulnerability remain poorly understood. Progress has been hindered by heavy reliance on subjective assessments of impulsivity and by the difficulty of dissociating changes in affective state from changes in action control. Here we propose a preclinical study in mice to examine how SSRI treatment dynamically alters impulsivity independently of affective processing. Using a validated mouse model of depression, we will longitudinally track impulsivity and depression-like behaviors before, during, and after chronic SSRI administration. To measure the dynamics of impulsivity, we will employ a novel behavioral assay that we have developed, which provides a robust, trial-by-trial quantification of impulsive responding. By characterizing the time course of SSRI-associated changes in impulsivity, this work will establish a translational framework for studying the transient elevation in suicide risk observed during antidepressant treatment.