The Corruptible Teenage Brain

The Corruptible Teenage Brain



The Corruptible Teenage Brain


The brain of an adolescent is no different in size or shape than that of an adult. On a standard CAT scan or MRI your brain and that of your teenage daughter would be indistinguishable. But, in terms of development, your brain is worlds apart from hers. Perhaps that is why the teen brain is more susceptible to drugs, alcohol and electronics.


The teen brain is different


Adolescents activate different brain regions during decision making when compared to adults.  Relatively increased activity in the striatum (a deep part of the brain that is considered a primary component of the reward system) and insula (a part of the brain active during psychological conflicts) is seen in the teenage brain. In the adult brain, on the other hand, the activity of the prefrontal cortex (the area responsible for executive function and rational decision making) predominated.

The anatomy of the teenagers’ brains is not fully mature. Certain cells of the brain (also called neurons or grey matter) send their signals via axons (a part of a neuron that is like the television cable that brings signal from one area to another). The axons (also called white matter) can leak signal unless they are insulated by a fatty substance called myelin.  Although the peripheral nerves, travelling through the body, are completely myelinated from a young age (allowing excellent physical coordination and strength), the axons of the brain do not become completely myelinated until the human brain fully matures at about twenty five years of age. The last part of the brain to become myelinated is the frontal lobe (responsible for executive functions). Because the wiring is not mature, the teen brain is more easily rewired (neuroplasticity) or disrupted.


Weed and the teenage brain


Several groups of neuroscientists have reported their findings regarding the effects of marijuana and the teenage brain:


One group of scientists studied the brains of 46 14-year-old girls and boys from Ireland, England, France and Germany. The results were startling. They found that weed damaged the brains of these children who reported using recreational marijuana only once or twice. The scientists examined the teens’ brains with MRI scans and found increased volume in numerous brain regions involved in emotion-related processing, learning and forming memories. 


Wait a minute. Increased volume? How could more brain be bad? 


The cortex (thinking part) of adolescent brains has an abundance of connections between neurons (brain cells). These excess connections transmit unnecessary signals that can create too much ‘noise.’ The connections need to be pruned so that the brain can function efficiently. If cannabis disrupts this pruning process, the brains of affected teens will not mature appropriately. The scientists reported that teenagers who regularly used marijuana were more likely than abstainers to have reduced scores on tests of memory, learning new information, and higher-level problem solving and information processing.


Another group of scientists reported their findings on 3,826 adolescent Canadian students. The researchers assessed the children annually for 4 years on alcohol and cannabis use, recall memory, perceptual reasoning, inhibition, and working memory. Those students who used cannabis, demonstrated inferior memory (both working memory and  delayed memory recall). The weed smoking children also lagged behind non users in testing of inhibitory control and perceptual reasoning. 


Marijuana has inordinate effects on the teenage brain. The process of brain development requires intense activity in neural  remodeling (neuroplasticity) which is impaired by cannabis use. This weed induced neurotoxicity may not wear off if a kid quits using marijuana. Evidence shows that cannabis may result in long-term brain impairment.


Alcohol and the teenage brain.


Evidence implies that alcohol affects memory and learning much more severely in adolescents than in adults. Investigators have demonstrated that, due to extensive changes and remodeling during adolescence, disruption of these processes by alcohol may lead to long-term alterations that influence adult behavior and responses to alcohol. Thus, when investigating alcohol’s effects on the adolescent brain, it is important to recognize that the immediate effects (e.g., memory impairment, motor impairment, or sedation) are only one piece of the puzzle. Alcohol also may cause irreversible derangements in adolescent’s future brain development. 


Alcohol interferes with the normal growth and pruning (plasticity) of synapses (connections between neurons (brain cells)) in multiple ways. NMDA and glutamate receptors (cell surface proteins that allow signals to pass) and LTP (strong and durable connections between cells) may be forever altered when the teenage brain is exposed to alcohol. Most severely affected is the hippocampus (part of the brain responsible for learning and memory). Neuroscientists have demonstrated that significantly higher concentrations of alcohol in the adult brain is required to damage the hippocampus, compared with the adolescent brain. 


Researchers have used animal models in several ways to demonstrate the long-term consequences of adolescent alcohol exposure on adult brain function. They have studied the brains of experimental animals under the microscope and also have measured the electrical brain activity of animals’ brains with electroencephalogram (EEG). The neuroscientists concluded that adolescence is a unique stage of brain development which is particularly sensitive to the disrupting effects of alcohol. They determined that, in rodents, the adolescent brain is especially sensitive to the alcohol effects on memory.


Studies in humans have found that alcohol abuse during adolescence may be associated with a reduction in the size of the hippocampus that persist throughout life. Alcohol disrupts a teenager’s ability to form new, lasting memories much more than it interferes with the ability to recall previously established memories. One group of scientists tested intoxicated youths and determined that volunteers could recall items on word lists immediately after the lists were presented, but they had greater difficulty recalling the information 20 minutes later. Furthermore, alcohol was particularly pernicious in diminishing the ability to memorize facts (who were you with last night?) and events (what were you doing that kept you out until dawn?). 


Drinking early, often and to excess.


According to the U.S. Substance Abuse and Mental Health Services Administration (SAMHSA), kids who start drinking before age 15 are five times more likely to become alcoholics or abuse alcohol than are people who abstain from alcohol until adulthood. Kids who drink are also much more likely than adults are to consume too much alcohol over a short period of time (binge drinking).


Binge drinking in teens is especially dangerous for many reasons. The prefrontal cortex (executive function area of the brain, responsible for attention, concentration, self-control and decision making) of teens is not fully developed. Motor vehicle accidents are much more likely in teens who have engaged in binge drinking. One in every 5 teen drivers involved in fatal car crashes have alcohol in their bloodstream (more than 80 percent have blood-alcohol levels above the legal limit). Also, teenagers who are under the influence of alcohol are much more likely to engage in unintentional and unprotected sex. Binge drinking may lead a teen to drink so much that alcohol poisoning stops them from breathing.


Teens and electronic devices


The current generation of kids is growing up with smartphones, tablets and other internet-enabled electronic devices. They have never known a world without sophisticated electronic devices or the internet, which may be why half of all adolescents report some level of addiction to digital devices. Many parents worry about the effect that screen time has on the developing brains of adolescents.

An extensive government sponsored study has been developed to determine whether screen time is bad for kids’ brains. Researchers from the National Institutes of Health have embarked upon the Adolescent Brain Cognitive Development (ABCD) study. Envisaged as a 10-year study, the largest ever of teenage brains, neuroscientists will subject kids to regular physical exams, cognitive tests and MRI scans at medical centers across the nation. The children and their parents also fill out detailed, confidential questionnaires about their habits and lifestyles.

Thus far, MRI scans have revealed significant differences in the brains of some children who reported using smartphones, tablets, and video games more than seven hours a day. In addition to demonstrable anatomical differences, children who engaged in more than two hours a day of screen time achieved lower scores on thinking and language tests.

Another group of researchers at the University of California at San Diego scanned teenagers’ brains while they checked their Instagram feed. The scientists reported that when teenagers viewed their Instagram feed, the reward system of their brains lit up. The scientists concluded that electronic devices can stimulate the release of dopamine, a brain chemical involved in cravings and desire.

A different group of neuroscientists have reported that teens who use electronic media at night are more at risk for sleep disturbances and symptoms of depression.

The effects of social media and video games on the brains of teenagers was the subject of a documentary called, “Screenagers.” It was reported that massive quantities of  dopamine were released into the brain’s pleasure center when teens were presented with new bits of information (text, images or video) and they gazed, wide eyed, at the screens.

The filmmakers documented MRI scans of the brains of kids who played 20 hours or more of video games a week. Evidence was presented that those teenagers’ brain scans were similar to those of people who are addicted to drugs or alcohol. Scientists concluded that the brain changes caused by excess screen time are anatomical (at a cellular level), not just psychological.


Animal studies have bolstered the evidence that the teenage brain is particularly susceptible to the pernicious effects of electronic addiction, especially in terms of damaging the capacity to learn new material. Adolescent mice exposed to rapid paced media required three times longer to learn how to go through a maze than non-exposed young mice. 


The good news is that the damage may not be permanent. Cutting back on screen time may relieve some of these symptoms. Researchers at the University of Pennsylvania investigated the psychological changes caused by electronic addiction college students. The scientists reported that students who limited their screen time to less than 30 minutes a day (for as little as 3 weeks) became less lonely and depressed.