Weed and Teens: How Cannabis Affects the Adolescent Brain and Body

Weed hits teens harder than adults because their brains are still developing until around age 25. Research links regular teen use to problems with memory, attention and learning, worse school outcomes, mental health issues and a much higher risk of addiction: about 17% of people who start in adolescence develop cannabis use disorder, versus about 9% of all users. As legalization and social acceptance spread around the world, how cannabis affects kids' physical, mental and emotional development has become one of the hottest questions in the debate.

Cannabis, marijuana, weed: is it all the same thing?

People still throw around all kinds of names for it in casual conversation and in the news, but "cannabis" has become the most common term for substances that come from the cannabis sativa plant.

"Marijuana" is often used interchangeably with "cannabis," but there's a technical difference. Marijuana generally refers to any part of the plant (or product) with significant levels of tetrahydrocannabinol (THC), the compound behind cannabis's psychoactive effects.

Worth noting: some people avoid the word "marijuana" because of its negative connotations and the anti-Mexican prejudice historically tied to it. And THC isn't the only active compound in cannabis: there are more than 100 cannabinoids, including the well-known cannabidiol (CBD).

Hashish, or hash, is made from the resin found mainly on cannabis flower buds.

The different forms of cannabis can be smoked, hit from a bong, or vaped with pens and other devices. It can also be added to food, drinks or candy to make edibles. Cannabis concentrates and oils can be inhaled too, which is known as dabbing.

How does weed affect teenagers?

The effects below depend on how much a teen uses, how often, for how long and at what age they started.

School performance

When a teen or child uses weed often, it can lead to trouble at school and dimmer prospects for college and a career. In fact, a review of 48 studies found that kids who use cannabis regularly are much more likely to drop out of school before graduating or earning a degree.

Lungs and airways

Like tobacco, weed smoke irritates the lining of the mouth, throat and lungs. It actually contains many of the same toxins and cancer-causing chemicals found in tobacco smoke. Smoking weed can trigger bronchitis, with coughing and mucus that can get in the way of healthy sleep. And vaping isn't risk-free for kids either: it comes with its own set of dangers.

The brain and puberty

One of the big concerns with teens and weed is that their brains are still actively developing, and will keep developing until around age 25. Cannabis's effects on the central nervous system can interfere with that development, which may cause:

• Trouble thinking and solving problems
• Problems with memory and learning
• Poor physical coordination and slower reaction time
• Trouble focusing and paying attention

A growing body of research suggests early exposure raises the chances of damage to some regions of the brain. Several researchers have pointed to disruptions in key processes like neurogenesis (the birth of new neurons), myelination, the migration of glial and nerve cells, the connections between neurons and the maturation of neurotransmitter systems.

These are essential for a healthy central nervous system, and recovering neuropsychological health can take months, even after someone stops using.

Using weed at a young age has also been linked to other changes, like gynecomastia (breast tissue growth in boys) and lower circulating testosterone with chronic use (though levels go back to normal after stopping).

In males, use may also affect sperm production and cause erectile problems. When exposure happens before puberty, it may delay its onset. Keep in mind that how sensitive the brain is during this stage varies from person to person.

Teen pregnancy

It's important to know that THC, weed's active compound, can cross the placenta, which can harm the fetus during pregnancy. Which raises the question: what problems could a baby face when a parent uses weed?

The harmful effects depend on when in the pregnancy exposure happens. In the first trimester, research has found it can lower fetal testosterone during sexual differentiation. When exposure happens in later trimesters, studies have reported slower fetal growth and damage to the developing brain.

That affects neurological development, showing up as a significantly smaller head circumference at birth and later linked to a range of issues in childhood and adolescence, like depression, anxiety, memory problems, attention-deficit/hyperactivity disorder (ADHD) and delinquent behavior in the teen years, though not necessarily in adulthood.

Mental health

Teen weed use has been linked to a range of problems, including depression, anxiety, suicidal thoughts and personality disorders.

One of the most talked-about links, though still controversial, is "amotivational syndrome": a drop in, or total loss of, interest in activities that are normally rewarding. Because the endocannabinoid system plays such a key role in regulating mood, these links need to be confirmed and clearly understood before anyone treats them as settled.

Everyday life

Driving, skateboarding, biking or playing sports while high can lead to serious accidents. Teens who are high may also take more sexual risks, which can have long-term consequences.

Addiction

A lot of people believe you can't get addicted to cannabis, but research says otherwise. About 9% of everyone who uses cannabis develops cannabis use disorder, but for people who start as teens, that rate jumps to 17%.

A substance use disorder is when a young person can't stop using, even when it's causing them problems or they want to quit. More than 55% of kids ages 12 to 17 who seek treatment for a substance use disorder are there for cannabis.

Cannabis-based medicines for kids with serious health conditions

Epidiolex, a drug made with a purified form of cannabidiol (CBD), has been shown to help control seizures caused by Lennox-Gastaut syndrome and Dravet syndrome.

After extensive testing, the US Food and Drug Administration (FDA) approved Epidiolex for kids ages 2 and up. Dronabinol and nabilone are FDA-approved, THC-based medications for chemotherapy-induced nausea and vomiting.

Our hope is that, with ongoing research, more cannabis-based medications will be developed, tested and reviewed by the FDA.

Teens and weed: the takeaway

Young people count on the adults in their lives to keep them safe and healthy.

With attitudes and laws around cannabis changing, the American Academy of Pediatrics (AAP) urges parents and caregivers to step up as advocates for young people and learn about both the positive and negative effects of cannabis. Getting the facts, keeping an open conversation going with your kids and, if you're worried about their cannabis use, reaching out to your pediatrician for guidance and support are the key steps.