The Teenage Brain: A Neuroscientist's Survival Guide to Raising Adolescents and Young Adults

Content Warning: This chapter contains outdated and offensive terminology for people with intellectual disabilities.

The author explains that a key feature of the teenage brain is its “neural plasticity.” This is the characteristic that gives adolescents great potential for learning but also makes them vulnerable. Jensen illustrates neural plasticity by recounting her experiences at two schools for children with cognitive disabilities. While in high school, she volunteered at the Association of Retarded Citizens (ARC)—now called The Arc to avoid pejorative terminology—in Greenwich. Located in an affluent area, the school was well-funded, and many of the children were from privileged backgrounds. Students took part in enriching activities, were almost independent, and made considerable educational progress. Later, when Jensen was in college, she volunteered at Belchertown State School, located in a disadvantaged area. Although the children had similar disabilities to those at the ARC, their experience was very different. The school was overcrowded and understaffed, and children made little educational progress. Jensen argues that her experience underlines the importance of nurturing the brain’s development.

The brain’s capacity to be molded has been demonstrated in many scientific experiments. In 1947, American neuropsychologist Donald Hebb compared the brains of pet rats allowed to roam the house and the brains of lab rats kept in cages. The former group performed significantly better in a maze test. As a student at Smith College, Jensen conducted experiments into “the plasticity of the visual cortex” in young brains (70). Kittens were exposed to safe and unsafe stimuli while also experiencing visual input in the form of either vertical or horizontal lines. As the kittens learned to associate safe stimuli with a certain type of line, the number of neurons in their visual cortexes grew.

Jensen describes the process of brain growth during learning. Information is stored in the short-term memory and compared to long-term memories. If the data already exists, it is discarded. However, new knowledge is sent to one of the brain areas responsible for storing long-term memories. New information becomes more ingrained in the memory the more it is recalled and used. Jensen asserts that adolescence is an optimal time to learn new things and nurture talent. Research suggests that IQs can significantly change between the ages of 13 and 17 and can continue to increase beyond that stage. The author points out that it is also the time when the most can be achieved from help with educational or mental health issues.

The adolescent brain also has significant weaknesses. For example, teenagers’ relative lack of white matter compared to adults leads to deficits in focus, self-control, and ability to complete tasks. Jensen recommends giving teenagers clear, concise instructions. She also advises developing their organizational skills by providing calendars and telling teens to keep daily schedules. Finally, the author stresses the importance of setting limits, as the teenage brain cannot do so. For example, parents should limit time spent on the Internet and have access to usernames and passwords.

As young brains have more excitatory than inhibitory synapses, teenagers crave new sensations. Consequently, they are also more inclined to take risks. Jensen illustrates this point by citing a study in which adolescents were asked to predict the odds of experiencing certain negative events. Afterward, the real odds were revealed, and the experiment was repeated. Most of the teenagers remembered examples in which the risk was less than they originally estimated. However, few of them recalled cases in which the danger was greater than their prediction. The research suggested that teenagers are more likely to make dangerous mistakes and less likely to learn from them.

Parents often complain that teenagers go to bed too late and are reluctant to get out of bed in the morning. Jensen points out that this is not a sign of laziness. Sleep patterns are governed by the brain and hormones, and adolescents are naturally wakeful later at night. Teenagers release the sleep-inducing hormone, melatonin, two hours later than adults. Melatonin also remains in their bodies for longer, meaning they are hard to wake.

By necessity, teenagers adhere to a timetable built on adult sleep patterns. However, rising early to get to school does not change the in-built body clocks of adolescents. They remain wakeful after adults go to bed, meaning their sleep period is shortened. Only at weekends do teenagers follow their natural circadian rhythm, falling asleep and waking late. Jensen advocates starting the school day later to better accommodate teenage sleep patterns. Research studies show that delaying a school’s start time by one hour improved students’ grades and attendance and made them less prone to depression. Students were also involved in fewer car crashes.

Sleep is the period during which the brain assimilates what has been learned in the day. Research suggests that sleeping on new information increases memory retention. For this reason, it is important for teenagers to get a good night’s sleep between revising and sitting an exam. Meanwhile, sleep deprivation causes impairment of memory. Due to rapid developments in the brain, teenagers need more sleep than adults. Adolescents require an estimated nine to 10 hours of sleep but typically fall short of that figure by almost three hours daily.

Jensen states that sleep deprivation can have numerous adverse effects on teenagers, impacting their mood, cognitive abilities, and health. Sleep-deprived adolescents are more susceptible to depression, aggression, impatience, impulsiveness, low self-esteem, and mood swings. They are also vulnerable to physiological conditions such as acne, overeating (and, therefore, obesity), sports injuries, and raised blood pressure. Cognitively, sleep-deprived teenagers may display restricted learning capacity, slow problem-solving, and impaired recall. They are also more likely to develop unhealthy habits such as smoking, drinking alcohol, and using marijuana.

Surveys suggest that between 30 to 50% of teenagers use artificial stimulants to stay awake. Some stimulants, such as Ritalin, are illegal if not prescribed for a medical condition. However, Jensen points out that highly caffeinated energy drinks are both legal and readily available, despite a dramatic rise in hospitalization cases from caffeine overdoses. The author argues that energy drinks are particularly dangerous when combined with alcohol. As drowsiness is suppressed by caffeine, teenagers remain active after drinking and are more likely to attempt to drive.

Jensen concludes the chapter with advice on how parents can help teens to get enough sleep. She recommends encouraging teenagers to organize and complete homework when they return from school and calmly check on their progress through the evening. A relaxing bedtime routine should also be encouraged. This entails removing TVs, computers, and cell phones from the bedroom. At the same time, conflict with teenagers before bedtime should be avoided.