But in terms of treatment this paperwork leads to several problems. Firstly, clients do not always know how to experience, express and report their own feelings. Secondly, such a survey is a (weekly) snapshot, while an anxiety disorder or depression, for example, can be very changeable. Thirdly, such a survey simplifies the complexity of mental health in a certain way. What is actually happening in the mind and the (social) life of the client? The comparison of personal data collected via social media, smartphones or wearables with big data can lead to an entirely new, tailor-made approach to psychological treatment.