Anyone who’s ever so much as met a teenager will know the turbid relationship between teenagers and sleep. At 10pm, they couldn’t be further apart, yet come 7am, they’re inseparable from their bedsheets. Is this because of their penchant for video games and Facebook which draw their eyes until the early hours of the morning? Is it because they’re just plain lazy, or are they zombie-vampire hybrids, sleeping by day, and eating all your food by night? And can these strange sleep patterns, consisting of late nights and unwanted early starts thanks to school and university really be healthy?
In a recent talk as part of the British Science Festival in Bradford last week, Paul Kelley, from the Sleep and Circadian Neuroscience Institute at the University of Oxford, asked us to describe adolescents (defined here as anyone between the ages of 14 and 24) in three words. Responses ranged from “hormonal” and “tired” to “developing” and “changeable”. Both types of responses instantly outlined the rest of the talk: adolescents are renowned for being tired, moody, lacklustre and hormonal, but we’re also aware that this is a very formative period of a person’s life: adolescents are still developing, both physically, and mentally, all the while showing these strange sleep patterns of late nights and late starts.
“Your body is not looking at a watch in order to set its time” says Dr Paul Kelley; during his British Science Festival talk, he explained that our bodies have their own 24 hour body clock, called a circadian rhythm, which plays a role in when we wake, and when we fall asleep, and therefore when we feel the most and the least alert in the day. Our body clock is biologically programmed by the SCN, the body’s pacemaker, which resides in our hypothalamus of the brain, and responds to environmental cues like light and temperature. Meanwhile, our watches are determined by society’s clocks: the times set by the school day, or the work day. When these two clocks, the biological and the societal, don’t match up, this can cause sleep deprivation and can lead to huge health consequences.
While we all have a biological body clock, they’re not all set to the same time. Our circadian rhythms change with age, making the body clocks of teenagers and adults vastly different. During adolescence, teenagers’ body clocks undergo a shift, as melatonin, a hormone which is secreted in large quantities towards night time and which regulates the sleep cycle, is produced later in the day in teenagers than in adults, altering their body clocks, and preventing them from sleeping until later. “To imagine how a 7am wake-up feels to a person in their late teens, imagine waking up at 4am.” While a 55-year-old might feel wide awake at 9am, a teenager whose body clock prevented them from sleeping until after 11pm, and who woke up at what felt to them like 4am, is likely to feel tired.
Of course, habits like texting or watching videos on laptops shortly before bed further exacerbate the problem of sleep deprivation in young people, as the blue light emitted by electronics prevents melatonin from being produced, therefore delaying sleep. So when a teenager, feeling untired at 10 or 11pm decides to occupy themselves with video games, or social media, this makes it even harder for them to get to sleep, pushing back their bed time further and making it even harder to wake up in time for school.
With as little as six hours of sleep (compared to the recommended amount of eight and a half hours) for a teenager who falls asleep at half past midnight and wakes at 6:30am for school, it’s no wonder teenagers are so tired. It is estimated that around 40% of teenagers are sleep deprived, and this can have serious consequences, such as impaired immune function, anxiety, depression, and has also been linked to diabetes, high blood pressure and obesity.
Sleep deprivation and tiredness also have unpleasant consequences for society as a whole, and not just the tired individual. The most common time for car accidents to occur is at 2pm: the same time that many adults feel a “slump” in their alertness. Meanwhile, adolescents have been found to have a high rate of car accidents in the morning, which is uncommon in adult drivers. To combat this, a school district in Kentucky moved start times from 9am to 10am, and saw a 16.5% decrease in the number of car crashes involving 17-18 year olds. Experts believe that this could be because 10am is a much more “friendly” time for adolescents to start school or university.
Now, back to the “changeable” and “developing” brains and bodies of 14-24 year olds. Studies involving the comparison of identical and non-identical twins have found that the areas of the brain which are heritable change with age. This means that while a part of the brain may begin by being mostly inherited and therefore determined by genetics, with age, this area might change to become more influenced by the environment, as less genes are “switched on” or active, and this section would be less similar between identical twins. Equally, areas which don’t seem to be dictated by genetics in childhood can later become more influenced by genetics, as more genes become “switched on”. Scientists think that this might be one of the reasons that schizophrenia usually doesn’t manifest itself until adolescence or adulthood. While schizophrenia is inherited, it is thought that the area of the brain involved in schizophrenia may become more heritable, and more influenced by genetics at this time, while in childhood, the genes involved in schizophrenia might not be active.
Over 50% of mental illnesses manifest themselves during adolescence. Some scientists believe that this might be due to the previously mentioned “changeable” nature of the brain, and are concerned that the sleep-deprived state of most adolescence might be a factor in this. However, evidence is currently unclear. This is one of the reasons that some scientists and educators have suggested that schools and universities begin no earlier than 10am. They are concerned that while an 8:30 or 9am start might seem perfectly reasonable to adults and children, for those in the 14-24 age bracket, this can feel as much as 3 hours earlier, as if they were starting school before 6am. They have suggested that if we want to improve both the learning experience and health of adolescents in education, it might be beneficial to change school times.
Adolescents’ troublesome relationship with sleep might not be entirely of their own devising. Being tired and sleep-deprived may not be so much a “natural part of being an adolescent”, but might be a symptom of this potentially harmful mismatch between their body clock and their society’s schedule.