The Effects of Marijuana on the Teenage and Young Adult Brain

Many use marijuana for the mind-altering effects of tetrahydrocannabinol (THC), a naturally occurring, psychoactive compound found in certain species of the Cannabis plant family.¹ In fact, cannabis (marijuana) is one of the most widely used substances in the United States. According to the 2021 National Survey on Drug Use and Health, 11.8 million young adults aged 18 to 25 reported using marijuana in the past year. In 2022, the Monitoring the Future Survey of middle and high school students found that 30.7% of 12^th graders reported using marijuana in the past year, a number that remained consistent from the previous year but decreased from 2020.² Of those 12^th graders, 6.3% of them reported daily marijuana use.¹

Marijuana Use Among Teens and Young Adults

With a growing number of states legalizing marijuana for medicinal or adult recreational use, perceptions of the risks, benefits, and social acceptability associated with its use have changed—among adults and teens, too.³

Marijuana is the most widely used among adolescents.³ Research suggests that such widespread use may reflect, at least in part, prevalent social norms amongst teen and young adults, the perceived risks and benefits of the drug, as well as frequent exposure to pro-marijuana messaging.³ Additionally, this group may use marijuana under peer pressure or to cope with stress, anxiety, even depression.⁴

Of the 52.5 million individuals aged 12 or older, who reported using marijuana in 2021, 35.4%—the largest percentage of all marijuana users—were young adults aged 18 to 25. Adolescents aged 12 to 17 accounted for 10.5% of that 52.5 million.⁵

Young people may use the dried flowers, leaves, stems, or seeds from the Cannabis plant, where marijuana derives, in several ways.¹ They may smoke it in joints (hand-rolled cigarettes), in pipes or bongs (water pipes), or in blunts (emptied cigars filled with marijuana). They may inhale marijuana vapors, rather than smoke, by using a vaporizer or e-cigarette, as well as eat it after mixing it into brownies, cookies, or other edibles.¹ Additionally, smoking or eating THC-rich resins that have been extracted from the cannabis plant have become increasingly popular methods of consumption.¹

Adverse Effects of Marijuana on the Developing Brain

When an individual smokes marijuana, the THC, the primary psychoactive chemical, rapidly crosses the lungs into the bloodstream, where it is then carried to the brain. When someone eats or drinks marijuana, the body absorbs THC more slowly. Regardless of the method of ingestion, however, when THC makes its way to the brain, it acts on specific cannabinoid receptors that otherwise interact with naturally occurring, endogenous cannabinoid substances, which play a role in normal brain development and function.¹

The human brain continues developing through age 25.⁶ Thus, marijuana use during adolescence and young adulthood may affect this development and can lead to impaired learning and memory by impacting how the brain builds connections between the areas necessary for these functions.¹

Adolescent brain development that continues into the early adulthood years focuses on fine-tuning neural pathways that contribute to brain maturity and developing the prefrontal cortex, which is responsible for assessing situations, making sound decisions, and controlling emotions and impulses.^7,8 The brain’s endocannabinoid system, a signaling system in the body and brain, plays a critical role during these developmental changes.^7,8

THC and other chemicals bind to the endocannabinoid receptors, and the resultant dysregulation of this neurotransmitter system could potentially result in long-term neurodevelopmental changes.⁸ Studies exploring the long-term effects of adolescent marijuana use on cognition, brain structure, and brain functioning compared to adults, suggest that the adolescent brain is far more sensitive to the chemicals in marijuana than the adult brain.⁸ Additionally, research indicates that chronic marijuana use during adolescence can lead to a loss of IQ that isn’t recovered even if the individual stops marijuana use in adulthood.⁷

Long-Term Dangers and Risks Associated with Teenage and Young Adult Marijuana Use

Chronic, early cannabis use is associated with several adverse effects that can impact an individual’s life—in adolescence, young adulthood, and beyond—including:^1,4

• Cognitive problems, such as problems with attention, concentration, problem-solving, learning, and memory.
• Reduced coordination and reaction time.
• Performance issues at school or work.
• A greater likelihood of dropping out of school.
• Poor decision-making and judgement.
• Relationship problems.
• Overall lower life satisfaction.
• Increased risk of depression, anxiety, and suicidal thoughts.

Furthermore, while marijuana may appear to be relatively less addictive than other substances that often dominate headlines, regular exposure to high amounts of THC through marijuana or THC resins can lead to addiction.¹ The risk of developing a marijuana use disorder, a diagnostic term for a marijuana addiction, may be higher in individuals who start using marijuana during youth or adolescence and who use it frequently.⁶ In 2021, nearly 5 million young adults aged 18 to 25 and 1.3 million adolescents aged 12 to 17 had a diagnosable marijuana use disorder.⁵

Signs That Your Child May Be Misusing Marijuana

Signs that your teen or young adult might be misusing marijuana often surface as noticeable behavioral changes. Indications of use can include but are not limited to:⁴

• Unusual laughing.
• Coordination problems.
• Forgetfulness.
• Bloodshot eyes.
• Clothes that smell strange, or a room filled with a distinct odor.
• Frequent use of incense or other deodorizers.
• A sudden wardrobe shift that includes drug-themed clothing and accessories, or adding drug-themed décor to their room.
• An increased need for money.
• The possession of drug paraphernalia or marijuana.

Getting Your Child Treatment for Marijuana Misuse

Unfortunately, many teens and young adults don’t seek treatment. For example, of the 5 million young adults aged 18 to 25 with a marijuana use disorder in 2021, only 28,000 received treatment.⁹

It’s not easy to admit you struggle with marijuana use. Young people may worry about punishment from parents or judgement from peers. Thus, recognizing the signs of marijuana use can provide a starting point for you to have a conversation with them about their misuse and getting help.

American Addiction Centers (AAC) has numerous accredited treatment centers across the nation available to help anyone aged 18 and older, who struggles with marijuana misuse. Call an AAC treatment center today at to start the path to recovery. A better future is available for your child, and you can help them get there.