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

A report from the US Surgeon General’s office estimates that 90% of new smokers are under the age of 18. Cigarettes contain many toxic chemicals, including carbon monoxide, arsenic, ammonia, and cadmium, and lung cancer is the main cause of preventable death in the United States. Jensen discusses the link between smoking and cognitive impairment. Research shows that consistent smoking impairs the normal development of the brain, leading to less active frontal lobes which, in turn, causes poor judgment. A study identified a correlation between smoking and lower IQs in adolescents, even when exposure to tobacco was secondhand. The author claims that smoking can also cause behavioral issues such as attention deficit hyperactivity disorder.

Jensen points out that smoking appeals to teenagers for several reasons: it seems exciting, it relieves stress, and it is seen as a social activity. Also, the health consequences seem so remote to a teenager that they appear irrelevant. Due to the plasticity of the adolescent brain, nicotine has a greater effect. This makes it difficult for teen smokers to give up once they have started. Research found that just one cigarette a month was enough to cause adolescent addiction. Withdrawal symptoms include sleep problems, difficulty concentrating, and irritability.

Research on rats shows that exposure to nicotine in adolescence damages serotonin-producing pathways in the brain. Lack of serotonin is the leading cause of depression, and tobacco addiction is common in individuals with mood disorders. Adolescent smokers are three times more susceptible to alcohol use and show increased alcohol tolerance. This means that teenagers are likely to drink more, leaving them vulnerable to alcoholism.

Jensen instructs parents to model good behavior by abstaining from smoking and talking to teenagers about its dangers. The author advises explaining tobacco’s effects on the adolescent brain. She also suggests emphasizing other disadvantages. Teenagers should be reminded that smoking is expensive, stains the teeth, impairs sporting ability, and makes clothes and breath smell. Jensen assures readers that, while teenagers may appear to be uninterested, they will absorb repeatedly stated messages. In the case of adolescents who already smoke, parents should suggest less harmful substitutes such as e-cigarettes or smokeless tobacco.

Content Warning: The following chapters discuss drug and alcohol addiction.

Every year, around 5,000 under-21-year-olds die from alcohol consumption. To illustrate teenage attitudes toward alcohol, the author gives the example of 17-year-old student Taylor Meyer. Taylor drank rum and 10 cans of beer before leaving a party near an abandoned airport. She was later found 100 yards from the party, having drowned in a muddy puddle. Only a week after her death, many of Taylor’s social group were found intoxicated near the area where Taylor died, wearing bracelets commemorating their deceased friend.

Jensen reveals that in the USA, the average age to start drinking alcohol is 14. Teenagers often binge drink, consuming four or five alcoholic drinks within a period of approximately two hours. The behavior of peers is also shown to have an impact on drinking habits, as teenagers often match the quantity they believe their friends are drinking. However, researchers have discovered that adolescents frequently overestimate the amount their friends drink.

The author challenges the common perception that teenagers quickly recover from drinking excessively. She acknowledges that the teenage brain deals better with the “short-term” effects of alcohol such as sleepiness, reduced physical coordination, and hangover symptoms. However, increased tolerance often leads adolescents to drink more and, in the long-term, impairs cognitive function and mood. Studies have linked teenage alcohol abuse to memory problems, attention deficit disorder, depression, and lack of drive.

Jensen explains that alcohol use affects the growth and efficiency of the frontal lobes, the hippocampus, white matter, and synapses. Damage to the white matter impairs problem-solving abilities, while alcohol impacts the hippocampus by causing memory loss. In relatively small amounts, drinking alcohol may lead to forgetting names or details of conversations. However, many teenagers binge drink, and the more they drink, the more severe the impact on long-term memory. In a survey, over 50% of college students questioned admitted to experiencing an “alcoholic blackout.”

A report in the Journal of Substance Abuse suggests that 40% of children who start drinking before the age of 13 develop alcoholism. Research shows that approximately 50% of the risk of alcoholism is genetic. However, Jensen states that environment accounts for the other half. The author claims that adolescents with parents who strongly disapprove of underage alcohol use are less likely to drink. She also challenges the belief that teenagers who are allowed to drink at home develop a more responsible attitude to alcohol. Research suggests that teenagers’ overall alcohol consumption rises in direct correlation to how much their parents allow them to drink at home.

Jensen reveals that when her sons lived at home, she installed a lock on the liquor cabinet. She also presented the facts about drinking to her teenagers, illustrated with real-life stories, such as that of Taylor Meyer. The author suggests that it is not enough to police teens’ alcohol use at home. She points out that other parents may have a less responsible attitude to underage alcohol consumption. For this reason, Jensen always called the parents of her sons’ friends in advance to check that sleepovers and parties would be supervised.

In the USA, marijuana is often used as a painkiller and is legalized for recreational use in some states. However, many neuroscientists believe pot is a “gateway drug” that can lead to harder drug use. Studies also show that smoking marijuana can damage IQ, and its abuse is rising in young people. The author believes that the relaxing properties of marijuana appeal to teens as they suffer more stress.

Jensen explains that the cannabis plant contains molecular compounds called cannabinoids, which include tetrahydrocannabinol (THC). It is THC that primarily causes the effects of marijuana. Clumsiness is caused by THC affecting the cerebellum. Meanwhile, slurred speech and distortion of perception result from its impact on the sensory areas of the brain. Although marijuana usually reduces anxiety, it can conversely prompt paranoia and depression. High doses can lead to a lack of motivation, confusion, and hallucinations.

As the brain naturally produces endocannabinoids, THC affects the many endocannabinoid receptors in the brain, interfering with brain function. THC inhibits the motor cortex, causing slow movement and difficulty in responding quickly to danger. Forgetfulness is also a common cognitive side effect. Most importantly for adolescents, THC “disrupts the development of neural pathways” at a time when the brain is still developing (145). Consequently, brain volume and gray matter may be reduced while white matter is damaged. As THC affects the frontal lobes of the brain, this may impact self-control, abstract thinking, and decision-making.

The side effects of marijuana are more intense the earlier a person starts using the drug. Jensen argues that adolescents are more likely to become addicted due to the intensely heightened reaction in the teenage brain when THC overstimulates the amygdala. This age group is also more likely to try harder drugs while under the influence of marijuana. Furthermore, various studies have linked marijuana use to mental illness. Scientists believe that adolescent use of the drug increases the risk of schizophrenia and psychosis and makes teens vulnerable to anxiety and depression in later life. Jensen suggests the reason for this is the way marijuana changes the receptors in the adolescent brain.

The author reveals that marijuana contains three to five times more smoke, tar, and carbon monoxide than tobacco and at least 50% more carcinogenic chemicals. She explains that the use of a bong only moderately reduces risk, as benzopyrene (the major carcinogenic in marijuana) does not dissolve when filtered through water. The author warns parents who may have experimented with marijuana that the drug is more potent and addictive than 20 or 30 years ago.

Jensen advises parents to be honest with teens about their own marijuana use while explaining that its negative effects on the brain were not then appreciated. Adults should emphasize how drug use might affect teenagers’ prospects and explain that it is not a sustainable way to deal with anxiety. Research suggests that disappointing their parents is a teenager’s biggest barrier to drug use. For this reason, Jensen urges parents to repeatedly discuss the subject with adolescents.

Every year, a candlelit ceremony is held outside the Drug Enforcement Agency headquarters in Virginia. Named “Vigil for Lost Promise,” the event is attended by the family and friends of individuals who died from illegal or prescription drugs. Many of those commemorated are teenagers.

Jensen recounts the story of 14-year-old Irma Perez. After taking ecstasy at a party, the teenager was in great pain and distress. Friends prolonged her suffering by delaying calling an ambulance for hours. Instead, they gave Perez marijuana, hoping it would counteract the effects of ecstasy. Perez died five days later from swelling in the brain. Following her death, four adolescents and a 20-year-old were charged with supplying the drug, failing to seek prompt medical assistance, and concealing drugs after her death.

The results of a 2011 survey suggest that ecstasy use has increased by 67% in teenagers. Otherwise known as MDMA or “molly,” Ecstasy is popular with young people as it intensifies sex, emotions, and feelings of intimacy or connection. Negative side effects are numerous, including distress, disorientation, disrupted heartbeat, seizures, organ damage, and death. Research shows that regular adolescent use of ecstasy inhibits the development of white matter and the hippocampus, resulting in damaged short-term memory and learning capacity. The drug’s impairment of serotonin production (the neurotransmitter that regulates mood) can also cause depression. Experiments show that ecstasy causes widespread changes in the brain’s synapses, leading teenagers to become addicted more quickly.

Cocaine is another addictive drug that affects the chemistry of the adolescent brain. Experiments in adolescent rats found that the stimulant permanently changed their brain structure. Cocaine creates a high by increasing levels of dopamine, and in teenagers this effect is intensified. The adolescent nucleus accumbens (the brain’s reward center) and the dorsolateral striatum (the habit-forming part of the brain) are particularly sensitive to cocaine’s effects.

Amphetamines and methamphetamines are also popular drugs among adolescents. Like cocaine, these stimulants produce a high by increasing levels of dopamine in the brain. However, Jensen reveals that the fastest-growing drug in American high schools is heroin. The author cites the case of Ian Eaccarino, who overdosed on heroin nine months after first trying it at college. Before his death, Eaccarino told his mother that he became addicted at college, where drugs were readily available and often given out for free.

Prescription drug abuse is also rising in the USA. Ritalin, prescribed for ADHD, is abused for recreational purposes. The same applies to sedatives such as Valium and Xanax and painkillers like OxyContin. Jensen explains that some adolescents become addicted to drugs like heroin after taking painkillers for sports injuries. Once hooked on painkillers, teenagers require larger doses or stronger drugs to create the same effect. Giving up is particularly challenging as the symptoms of withdrawal are worse in adolescents. Consequently, the author suggests caregivers should resist giving adolescents painkillers unless absolutely necessary.  

Jensen asserts that drug abuse in adolescents requires “aggressive intervention” and prompt medical treatment. Parents need to be aware of warning signs such as changes in appetite and sleep patterns, irritability, and a decline in personal hygiene. The author recommends the website of the National Institute on Drug Abuse—www.drugabuse.gov—as a source of information. She also suggests that suspicious parents should search their teenagers’ rooms while they are out.