RecruitingPhase 2Drug trialClemastine for Improving White Matter and Boosting Antidepressant Response in Late-life DepressionThe goal of this study is to find out if the antihistamine, clemastine, can make the white matter in the brain better in older adults with depression. The study will also determine whether this improvement can make antidepressant treatment work better, reduce depressive symptoms, and improve memory and thinking.