There is a myth that adolescents need less sleep than they did during their younger years. False. Teenagers need nine or ten hours of sleep every night. Most are sleep deprived. They can become increasingly cognitively impaired across the week, even though sleep is thought to be critical for the reorganization of the teen brain. Sleep deprivation tends to exacerbate moodiness and cloudy or erratic decision-making. Part of the problem can be laid at the feet of early bussing and class schedules. Part of the problem involves a shift in circadian rhythms during adolescence. Teenagers do better when they stay up later and get up later. They often stay up later but still have to get up earlier, which contributes to sleep deprivation—and the results of sleep deprivation can be ugly. Sara Johnson, an assistant professor at the Johns Hopkins Bloomberg School of Public Health who reviewed the neuroscience in The Teen Years Explained: A Guide to Healthy Adolescent Development by Clea McNeely and Jayne Blanchard, encourages parents to continue to parent their adolescents. Like all children, "teens have specific developmental vulnerabilities and they need parents to limit their behavior," she said. The good news is as the brain develops, the opportunity for parents and children to become good friends, also can emerge.