Project Summary / Abstract Over 15 million Americans serve as family caregivers of relatives with Alzheimer’s disease (AD) and AD- related dementias (ADRD). Family caregivers often experience high levels of stress and burden, resulting in poor mental health and increased risk of physical illness. The National Institute on Aging Strategic Plan identifies as a crucial priority area the need to develop better interventions to improve the mental and physical health of family ADRD caregivers. The purpose of this administrative supplement is to support the research training of Dr. Felipe Jain, a psychiatrist at Harvard Medical School. Dr. Jain is a recipient of the Paul B. Beeson K76 Emerging Leaders in Aging Research Career Development Award for his research to reduce family ADRD caregiver stress and burden using mobile application tools (mentalizing imagery therapy practices, mindfulness exercises and caregiver skills education). Usage of educational and psychotherapeutic mobile applications (Apps) by caregivers shows a significant drop-off in engagement over the course of weeks, a similar pattern to that of mobile psychotherapy App usage by the general population. The NIH Science of Behavior Change initiative aims to study mechanisms that promote long-term adoption of healthy behaviors, such as engagement with stress reduction and caregiver skills tools. A focus group study conducted by Dr. Jain with English and Spanish speaking caregivers found that caregivers believed that asynchronous chat groups with peers guided by an expert facilitator would substantially improve caregiver support and increase mobile App engagement. This supplement proposal will evaluate whether integration of a new facilitated chat room feature into a mobile App with caregiver tools improves family ADRD caregiver support and promotes long-term engagement. The study will characterize features that optimize usage of the mobile App chatroom. Based on habit formation and motivation theory, it is hypothesized that chatroom participation will increase long- engagement with other healthful mobile App tools. To improve efficiency and reduce time to facilitator response for urgent chat posts (such as those reflecting dangerous symptoms of aggression in the person living with dementia, or severe psychological symptoms in the caregiver such as thoughts of self-harm), a natural language processing algorithm will be developed that may ultimately send a rapid alert to the facilitator. The proposed research will test a novel strategy for behavior change that improves psychosocial support for family ADRD caregivers, provides opportunities for expert guidance, and promotes stress reduction and caregiver skills education.