This study investigates how smartphone usage and mental health are statistically related by monitoring students’ smartphone use (using a dedicated passive logging app) and experience sampling 1) procrastination, fatigue, stress, and happiness 5 times daily and 2) sleep duration and quality and active study time (daily). The study comprises two measurement bursts, each of which has a duration of 30 days. Alongside these measures, we ask participants to report grades (non-compulsory). In 5 waves, we measure depression, burnout, and body dysmorphic symptoms. Smartphone use will be logged from the measurement burst and cross-sectional surveys until at least the final day of the second measurement burst. The study aims to test if there are short-term as well as long-term temporal relations between smartphone use, procrastination, fatigue, stress, and sleep (duration and quality). We will further test whether there are interindividual differences in these relations.