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

The impact of concussions on the brain has recently gained attention in the arena of professional sports. However, Jensen suggests that there is little awareness of how brain injuries affect adolescents. The author reveals that evidence increasingly shows that teenagers are particularly vulnerable to concussions. Adolescents’ brains react more extremely than adults to head trauma, and the effects can be long-lasting. At the same time, contact sports are becoming more popular in American schools.

Jensen recounts the case of a patient who was a high-achieving high school student until he suffered two concussions as a wrestler. Although a CT scan showed no obvious brain damage, the teenager experienced mood swings, headaches, and memory impairment. As a result, his grades declined, and he suffered debilitating anxiety. Neuropsychological tests revealed the concussions had caused “a learning deficit and inattention” in the patient (242).

Despite boys’ higher participation rates in high school sports, girls suffer 70% more concussions. Studies also show that girls take longer to recover from brain injury, displaying greater cognitive impairment. In 2010, Jensen received an email from a mother who was concerned about her 15-year-old’s seizures. Three years earlier, her daughter, Holly, suffered two concussions in quick succession while playing football. Afterward, she experienced headaches, passed out repeatedly, and had seizures that increased in length and severity. Jensen states that three factors brought on these severe symptoms in Holly: her age, her sex, and experiencing more than one concussion within a short time frame.

Jensen describes the mechanics of concussion. Cerebrospinal fluid in the skull protects the brain from being injured by everyday “jostling.” However, if the head jerks violently backward and forward, the fluid does not provide adequate protection. Consequently, the brain hits the inside of the skull, and neurons are damaged. A particularly forceful blow may cause the brain to hit both sides of the skull, known as a coup-contrecoup concussion. The author explains that scientists now recognize that concussions can occur without a discernible blackout. They also realize that head trauma can have a lasting impact even in the case of “closed-head injuries” when there is no sign of damage to the head or skull (239). Recent studies reveal that brain damage can be caused by successive, relatively small blows to the head that do not cause concussion. Jensen suggests that many children who play contact sports could have undiagnosed brain damage.

The prevalence of non-diagnosed brain injuries was unexpectedly illustrated by a study on concussions in high school football players. The scientists conducting the research needed to compare their findings with a control group of football players who had never suffered concussions. However, the brain scans of the control group also showed damage, indicating that most of them had suffered undiagnosed brain injuries.

Jensen explains that mild traumatic brain injury is difficult to detect, as the damage is “not structural” but “cellular” (245). The violent movement of the brain inside the skull causes the release of calcium and potassium, which, in large concentrations, damages brain cells and white matter. In addition to cognitive and physical side effects, mood can also be affected, leading to irritability, anxiety, and depression. The author notes that the pituitary gland (situated behind the bridge of the nose) is also easily damaged by head injuries. As the pituitary gland controls growth and metabolism, symptoms of post-traumatic hypopituitarism include fatigue, decreased muscle mass, depression, weakness, impaired memory, and reduction in sex drive.

The author notes that the risk of brain damage increases when an adolescent is concussed for a second time before they have fully recovered from a previous head injury. Recent research shows that the risk of anterograde post-traumatic amnesia (difficulty in forming new memories) doubles in teenagers who suffer multiple concussions. Jensen cites the case of 17-year-old football star Nathan Stiles. In 2008, Stiles experienced a headache after a head impact during a game, but a brain scan showed no damage. Three weeks later, the teenager suffered another blow but claimed to be fine. The following week, Stiles collapsed with seizures during a game. He underwent brain surgery but did not survive. When the teenager’s brain was analyzed, his neurons were shown to be damaged by tau protein—a common feature of Alzheimer’s disease. Scientists realized that Stiles had the youngest recorded case of chronic traumatic encephalopathy (CTE): a disease often associated with retired professional boxers. The teenager had likely suffered numerous undiagnosed concussions before his death.

In 2011, the Canadian Paediatric Society suggested that blows to the head, bodychecking (slamming players into the boards), and fighting should be banned from all youth sports. Given the vulnerability of the adolescent brain, Jensen supports this argument, pointing out that a brain injury can potentially ruin a teenager’s life prospects.

Content Warning: This chapter contains references to suicidal ideation.

In this chapter, Jensen considers to what degree adolescents should be held accountable for crimes. Every year, 200,000 adolescents between the ages of 12 and 17 are arrested for violent offenses. The author points out that some prisoners serving life sentences in the United States were 13 or 14 when they committed their crimes.

Jensen outlines the history of the legal system’s attitude to minors. She reveals that, until relatively recently, children were treated as adults. In the Middle Ages, children as young as six years old were hanged or burned at the stake. Meanwhile, the first recorded case of a juvenile receiving the death sentence in America was in 1642. In the 18th century, British judge and scholar William Blackstone took the first steps toward establishing a separate juvenile justice system in Great Britain and America. Blackstone argued that children of six years and younger could not be held accountable for crimes as they did not understand the implications of their actions. He suggested juveniles should only be tried as adults from the age of 15. However, this left a gray area between the ages of seven and 14. If offenders fell into this age group, Blackstone recommended they should be tried as adults, provided they understood “the difference between right and wrong” (261).

Children under the age of 14 continued to be executed in the United States into the late 18th century. Twelve-year-old Hannah Ocuish’s execution in 1786 is the youngest known case. Part Pequot and part African American, Hannah was found guilty of strangling a six-year-old white girl from a rich family. Evidence suggests that Ocuish may have had an intellectual disability.

In 1825, a “House of Refuge” for children was established in New York. This was the first official attempt at rehabilitating young offenders in the USA, and it marked the start of the reform school system. In 1899, the first juvenile court was established, creating a separate justice system for children and adolescents. However, abuses of that system came to light in the 1960s. Children often had no legal representation, and the sentencing of judges was frequently harsh.

Jensen reveals that a mass murder in 1966 brought the question of “biology and legal accountability” to the public’s attention (266). Twenty-five-year-old Charles Whitman was a former model citizen before stabbing his wife and mother to death and randomly firing at passers-by from the University of Texas Tower. Whitman killed 13 people and injured 32 before he was shot dead by police. In the aftermath, suicide notes by Whitman were found requesting an autopsy on his body. Whitman stated that he believed a physical disorder was affecting his thought processes, and a doctor had prescribed Valium for his depression and headaches. Whitman’s autopsy revealed a grade four tumor in his brain, affecting both the hypothalamus and the amygdala. Jensen explains the tumor may have caused “limbic overdrive,” leading to a rage that Whitman could not control.

Jensen cites the case of Roper v. Simmons as a landmark case in juvenile sentencing. Christopher Simmons was physically and emotionally abused by his stepfather, who fed him alcohol from the age of four. By his teens, Simmons was addicted to alcohol and also abused drugs. He frequently visited the trailer of a 28-year-old neighbor who fed his habit and encouraged him to steal. In 1993, 17-year-old Simmons and a younger boy broke into the home of 46-year-old Shirley Crooks. They bound and gagged Crooks, robbed her, and then drowned her by throwing her off a bridge. Simmons was given the death sentence but launched an appeal that went to the US Supreme Court. In 2005, the Supreme Court ruled that executing a juvenile was “a violation of the Eighth and Fourteenth Amendments of the US Constitution” (267), as well as a contravention of “standards of decency” (268).

Jensen suggests that there are several reasons why adolescents cannot be held to the same legal standards as adults. Due to the overexcitability of the hippocampus and amygdala, teenagers are likely to respond emotionally and impulsively in volatile situations. As their frontal lobes remain immature, adolescents are also less capable of responding reasonably and considering the consequences of their actions. Teenagers are also less able to assess the repercussions of “plea bargaining” and are susceptible to making false confessions. Furthermore, adolescents are more easily influenced by others. Studies show that witnessing or being a victim of violence makes teenagers more likely to commit a violent crime. Significantly, more than 50% of homicides committed by teenagers involve several accomplices.

The author explains that she first became professionally involved in the issue of adolescent legal responsibility when contacted by Terrance Graham’s attorneys. As a child, Graham had ADHD, and his parents were addicted to crack cocaine. At the age of nine, he was drinking, and by 13, he smoked marijuana. When Graham was 16, he and his friends were involved in a failed robbery at a barbecue restaurant. During the attempted theft, one of Graham’s friends assaulted the manager, causing a head injury. Graham was charged as an adult and served six months in prison. On his release, the teenager vowed to change his life. However, six months later, just before his 18th birthday, Graham was involved in two home invasions and attempted robberies. He was caught by the police after dropping his accomplice—who had been shot—at a hospital. Believing that Graham’s behavior showed a permanent tendency to criminality, the judge sentenced the teenager to life imprisonment. His legal team appealed the sentence, which reached the US Supreme Court. Graham’s attorneys needed scientific evidence of the difference in adolescent brains in order to show that he was not as legally accountable as an adult. Jensen supported the argument that a life sentence without parole was an unsuitable punishment for adolescents like Graham.

In 2010, the Supreme Court agreed that a life sentence without parole was inappropriate for juveniles charged with nonhomicide cases. However, teenagers involved in homicide could still be sentenced as adults. In 2011, Jensen became involved with another two cases that went to the Supreme Court, both involving 14-year-old boys charged with homicide. In Jackson vs. Hobbs, Kuntrell Jackson had attempted to rob a video store with two older boys, one of whom shot the clerk. In Miller v. Alabama, Evan Miller and a friend assaulted a middle-aged man and set fire to his trailer. In both cases, Jensen was asked to explain the role of immature frontal lobes in poor adolescent decision-making. The author also pointed out the effects of being raised in a violent, socially-deprived environment and argued that, due to brain plasticity, teenagers are more likely to be successfully rehabilitated. As a result of these cases, the Supreme Court ruled it “unconstitutional” for under-18s to be sentenced to life without parole, even for homicide. In the process, the statutes of 29 states were overruled.

Jensen concludes that the justice system has yet to adequately work out how to view juveniles and adults with mental disorders. She acknowledges that this is a complex area as it is difficult to separate behavior caused by the brain from factors such as formative experience and “socioeconomic status.” Furthermore, the age of full neuro maturation remains a gray area.

In 1970, psychologist Kenneth Keniston argued that there is an additional stage of development between “adolescence and young adulthood” (280). Jensen agrees, arguing that, as the white matter is still maturing, brains are not fully developed by the end of the teenage years. She suggests that the early to mid-twenties continue to be a period of turmoil and vulnerability as young adults work out who they are.

The author points out that, in the developed world, the post-adolescent age group now takes longer to finish their education, leave home, choose a profession, marry, and have children. Jensen suggests that taking a gap year before college is useful in helping young people to mature, learn, and become independent. Brains still have a high degree of plasticity at this stage. Consequently, young adults learn organizational and communication skills, as well as an increased sense of responsibility when they join the world of work. The author warns parents that the emergence of mental disorders is still common in this age group, but there are currently fewer services available to them.

Jensen states that the aim of her book is to help parents to understand their teenagers and summarizes her advice. The author says that parents should anticipate ill-judged behavior from their teens due to their developing brains and show tolerance. Mistakes should be discussed calmly, avoiding judgment. However, it is also important to set limits on behavior where necessary.

The author emphasizes the importance of keeping communication channels open. She advises talking to teens about the information in her book and trying to get to the bottom of any behavior changes. If other communication methods fail, she suggests texting. While acknowledging that the teenage years can be challenging, Jensen states that parents should remain as positive as possible. She recommends being involved in teenagers’ interests and conveying the exciting opportunities available to them during this stage of development. Brain plasticity should be exploited by encouraging teenagers to try new skills.

Jensen reminds parents that they are the primary role models for their children. Adolescents constantly absorb how parents behave and react to challenges, so it is important to set a calm and resilient example. The author illustrates her point by describing a devasting house fire her family suffered in 2000. Although the experience was traumatic, it ultimately enhanced her teenage sons’ belief that they could overcome anything as a team.