National surveys in Sweden point to that young women report more mental health problems such as anxiety and depression than young men of corresponding age, but also compared to women and men in older ages. Register data furthermore show that young women utilize psychiatric health care more than young men, and show higher levels of sick leave. There is a common opinion in Sweden and internationally that mental health problems have increased over the past decades. This increase is however poorly understood, calling for more rigorous studies to clarify extent and severity of the problems, but also, importantly, to inform practices on how to adequately assess youth mental health. The purpose of this project is to increase our knowledge about the mental health of young women and to establish a valid and comprehensive method for assessing mental health in young women that can improve our capacity to promote mental health and address mental health problems. To that end, we will apply a multimodal data approach, comprising a feasibility study on methods of assessment of mental health in young women. The specific aims of the proposed project are: 1) To determine the extent and course of mental health in young women over a two-year period and discern the added value of multimodal data to assess and predict mental health problems. 2) To demonstrate the feasibility of different assessment methods of mental health in young women. Establishment of feasibility is done by collecting data on: recruitment rate, adherence and acceptance of study procedures including mode of data collection. Data will be collected via a study-specific app, developed using the Beiwe research platform from the Harvard School of Public Health. Data collected will include 1) survey data on wellbeing, anxiety, depressive symptoms, sleep as well as sociodemographic and individual health data 2) survey metadata such as time taken to answer a specific measure and complete the full survey etc. 3) passive data such as from for example smartphone sensors and activity logs, 4) behavioural assessments done online, 5) data from Swedish national registers as well as 6) blood based biological markers will be linked to data collected by the app.