Alzheimer's Disease (AD) and Alzheimer's Disease-Related Dementias (ADRD) not only exact a heavy toll on patients, they also impose an enormous emotional, physical, and financial burden on unpaid, often family, caregivers. The strain of providing care for a loved one diagnosed with AD, often across several years, is associated with elevated depression risk and poorer overall health. Emotion regulation skills represent an ideal target for psychological intervention to promote healthy coping in ADRD caregivers. The project seeks to use an experimental medicine approach to test the efficacy and biobehavioral mechanisms of a novel, relatively brief, targeted, scalable, smartphone-based cognitive emotion regulation intervention aimed at improving psychological outcomes (i.e., reducing perceived stress, caregiver burden, and depressive symptoms) in ADRD unpaid primary caregivers as well as examine potential benefits of the caregiver intervention on quality of life in care recipients. Cognitive reappraisal is the ability to modify the trajectory of an emotional response by thinking about and appraising emotional information in an alternative, more adaptive way. Reappraisal can be operationalized via two primary tactics: psychological distancing (i.e. appraising an emotional stimulus as an objective, impartial observer) and reinterpretation (i.e., imagining a better outcome than what initially seemed apparent). The project will investigate the efficacy and underlying biobehavioral mechanisms of a novel, one-week cognitive reappraisal intervention in this population, with follow-up assessments at 2 weeks, 4 weeks, and 3 months. ADRD unpaid primary caregivers will be randomly assigned to receive training in either distancing, reinterpretation, or a no regulation natural history control condition, with ecological momentary assessments of self-reported positive and negative affect, remotely- collected psychophysiological health-related biomarkers (i.e., heart rate variability data) using pre-mailed Polar H10 chest bands, and health-related questionnaire reports. Distancing training is expected to result in longitudinal reductions in self-reported negative affect, longitudinal increases in positive affect, and longitudinal increases in HRV that are larger than those attributable to reinterpretation training and no-regulation control training.