Evening light exposure and sleep phase shifts in adolescence and childhood: Literature review

Abstract

Sleep regulation in children and adolescents relies on the interaction between homeostatic and circadian processes. The internal biological clock, located within the suprachiasmatic nuclei, is primarily synchronized by light. This light is detected by intrinsically photosensitive retinal ganglion cells (ipRGCs), which are highly sensitive to short-wavelength blue light. Evening exposure to LED lighting and electronic screens can suppress melatonin secretion, promoting sleep phase delay. Children and adolescents are exceptionally vulnerable to this effect due to both anatomical and developmental factors. Combined with cognitive arousal from social media and the Fear of Missing Out (FOMO), this creates a "perfect storm," resulting in behavioral bedtime procrastination and a natural shift toward an evening chronotype. While it is crucial to distinguish this common developmental and behavioral shift from a clinical disorder, cumulative circadian disruption and social jetlag remain significant risk factors for Delayed Sleep-Wake Phase Disorder (DSWPD). Furthermore, chronic sleep restriction exhibits observational associations with poorer academic performance, potential long-term metabolic disturbances (such as obesity and insulin resistance), and an elevated risk of mood disorders and depression. Available evidence highlights the critical importance of light hygiene, including limiting evening screen exposure and promoting morning natural light. Medical interventions, such as melatonin and chronotherapy, should be carefully reserved for severe clinical cases. Finally, future longitudinal studies utilizing personal light dosimetry are needed, alongside systemic solutions like delayed school start times, to protect pediatric sleep health.