BackgroundPeople with multiple sclerosis (pwMS) struggle with whether, how, and how much to disclose their diagnosis. They often expend resources to conceal their diagnosis, and hold beliefs that it may negatively affect their personal relationships and/or professional opportunities. To better understand these effects, we developed a measure to quantify concealment behaviors and disclosure beliefs. Our main objective is to evaluate relationships of DISCO-MS responses to health and quality of life in a multinational cohort. MethodsSurvey responses were obtained for DISCO-MS and PROMIS-MS scales: global health, communication, social roles participation, anxiety, depression, emotional / behavioral dyscontrol, fatigue, lower extremity function, positive affect / well-being, social roles satisfaction, sleep, stigma, upper extremity function, cognitive function, bladder control, bowel control, visual function. Simple linear regression assessed associations. Results263 pwMS were include. Higher concealment was associated with higher anxiety (beta= 0.15 [0.07, 0.23]), depression (beta = 0.13 [0.05, 0.21]), emotional dyscontrol (beta = 0.12 [0.04, 0.20]), lower affect / well-being (beta = -0.13 [-0.21, - 0.05]). Higher anticipation of negative consequences of disclosure was associated with lower self-reported physical (beta = -0.15) and mental health (beta = -0.14), lower positive affect / well-being, social roles satisfaction, higher anxiety, depression, emotional dyscontrol, sleep disturbance, and higher perceived stigma. DiscussionThese results reveal potential consequences of diagnosis concealment for physical and mental health and quality of life. Raising awareness and implementing interventions may mitigate negative repercussions of concealment.