Corresponding author e-mail: flouzada@ufpr.br Adolescents experience excessive daily sleepiness because they get an insufficient amount of sleep. An adolescent requires an average amount of daily sleep in the range of 8.5 to 9.25 hours. Studies of adolescents in several countries have shown that the students average sleep period is reduced during school days to around 7 hours due to a tendency of students to delay bedtime while maintaining the same waking time to adhere to school schedules. A partial sleep deprivation that averages 1-2 hours per day during school days is enough to trigger symptoms of sleepiness, leading to a reduced school performance. It is already known that excessive sleepiness impairs concentration and learning capacity. For many years, the phase delay was attributed exclusively to social factors: greater independence to organize their own schedules, access to technology (TV, video games, computers, and the Internet), and a greater demand for social outings and events. In the early 1990s, it was demonstrated that pubertal stages of development were associated with a delay in sleep times. According to the classification proposed by Tanner, more mature adolescents have more delayed sleeping times than less mature adolescents, regardless of the age factor. In order to identify the possible social factors involved in the expression of the biological rhythmicity during adolescence, we have carried out studies with rural populations, some of which do not have electric power at home, These results reinforce the major influence exerted by social factors upon the adolescent phase delay. The magnitude of this delay in urban populations, particularly those that have access to technological resources, is greater and, consequently, sleep deprivation during school days is also greater. Changes associated with pubertal maturation render the individual more susceptible to delays in sleep time. It is as if the same stimuli have a different effect depending on the function of the puberal stage. In more advanced puberal stages, the adolescents body is more sensitive to stimuli capable of promoting delays in the biological rhythms. We can thus conclude that not all adolescents are sleep deprived, only those who are exposed to contemporary society’s technological advances. Publication History Article published online: 16 June 2026 © 2009. Brazilian Sleep Academy. This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/) Thieme Revinter Publicações Ltda. Rua Rego Freitas, 175, loja 1, República, São Paulo, SP, CEP 01220-010, Brazil
FM Louzada (Thu,) studied this question.