Wearable devices offer a unique opportunity to provide real-time monitoring of affective switching (the mood transition into and out of dysregulated affective state), a critical window to detect and prevent depression and suicide. To model affective switching, we studied premenstrual dysphoric disorder (PMDD): a depressive disorder with a regularly occurring monthly trigger. Results supported feasibility of smartwatch monitoring protocol and preliminary evidence that objective physiological and behavioral metrics were associated with affective state.