​This project investigates how puberty and menstruation affect sleep quality in adolescent girls. Poor sleep is a major risk factor for mental and physical health, and menstrual problems may further increase vulnerability. While research exists in adult women, evidence in adolescents is lacking despite their high risk of poor-quality sleep. The project includes a systematic review and two observational studies. The review will summarize existing evidence on the menstrual cycle and sleep in girls aged 10–18 years. The first study will monitor sleep across menstrual phases in girls with and without hormonal contraception. The second will examine how early puberty affects sleep compared to peers. Data will be collected using wearable sleep monitors and questionnaires and analyzed with advanced statistical models. Findings will inform evidence-based strategies to improve sleep and wellbeing in adolescent girls.