A longitudinal daily diary study of stress, self-esteem fluctuation, and mood variability in adolescents.

Sleep is vital for children’s physical and mental growth and development [, ]. Several factors can negatively influence sleep, and recent studies have demonstrated an association between prolonged use of electronic media and poorer sleep quality [–]. Due to the growing digital market targeting children, concerns have increased regarding excessive screen exposure, particularly among young children (0–5 years), and its potential harmful effects [, ]. The American Academy of Pediatrics (AAP) has established recommendations for media use among children and adolescents with the objective of enhancing their quality of life [, ]. According to these guidelines, as well as those from the Brazilian Society of Pediatrics (BSP), screen time for children aged 2 to 5 years should be limited to a maximum of 1 h per day, and exposure should be avoided within 1 to 2 h before bedtime [, ]. In this context, sleep disturbances in early childhood have emerged as an important public health concern, as accumulating evidence suggests that poor sleep is associated with emotional and behavioral problems, deficits in attention, learning, and self-regulation, impaired neurocognitive development, increased risk of excess body weight, and adverse cardiometabolic outcomes [, , , , , ]. Because the preschool period represents a critical window for brain development and behavioral regulation, inadequate sleep may negatively affect both immediate health and long-term developmental trajectories [, , , , , ]. In addition, sleep bruxism is frequently associated with sleep disorders [] and is commonly reported in preschool-aged children, potentially contributing to tooth wear, orofacial discomfort, and headaches []. It has been associated with early signs of temporomandibular disorders.