The Intern Health Study is a longitudinal cohort study that assesses stress and mood in medical interns at institutions around the country, enrolling about 1500 new interns each year. Supported by the National Institute of Mental Health (R01 MH101459), the University of Michigan Depression Center and the Taubman Medical Institute. The Intern Health Study app is a research application used to collect information for use by the Intern Health Study. The app collects data through: SURVEYS: Participants will complete an initial survey (20 minutes) and short quarterly follow-up surveys (5 minutes) through the Intern Health Study App. Surveys will contain questions pertaining to personality traits, stressful life events, and depression. DAILY MOOD: Participants will receive notifications on their iPhone prompting them to rate their daily mood on a scale of 1 to 10. FITBIT: Some participants will wear a Fitbit Charge 2 for the purpose of measuring daily activity and sleep. Steps, sleep, and mood data for the past week will display on the app Dashboard screen. LOCATION: In order to obtain an objective measure of daily activity, we will request access to the ""frequent locations"" data that iPhones already collect using GPS - latitude, longitude, and time stamp. Continued use of GPS running in the background can dramatically decrease battery life. We have designed this study to ensure complete security and confidentiality of the information participants provide. An access code is required to use the application. Participants will receive an access code once they have been invited by the study. To learn more about the study visit us at www.internhealthstudy.org Fitbit is a registered trademark and service mark of Fitbit, Inc. This product is not distributed by Fitbit, and Fitbit does not service or warrant the functionality of this product.