Caffeine raises blood pressure, disrupts sleep, and can interfere with brain development in children and teenagers. Because kids weigh less than adults, even moderate amounts of caffeine produce stronger effects, and their developing brains are more vulnerable to those effects than a fully mature adult brain. The American Academy of Pediatrics recommends that children avoid caffeine entirely.
Blood Pressure Goes Up, Even in Healthy Kids
When children and teenagers consume caffeine, their blood pressure rises within the first hour and stays elevated for several hours. In a randomized trial published in Frontiers in Cardiovascular Medicine, healthy young people who drank a caffeinated energy drink saw their systolic blood pressure (the top number) climb by about 5 mmHg compared to a placebo, with the increase persisting for at least four hours. Their diastolic pressure (the bottom number) rose by about 3 mmHg. That may sound small, but for a child whose baseline blood pressure is already lower than an adult’s, it represents a meaningful shift in cardiovascular workload.
Interestingly, heart rate did not increase in that study. It actually trended slightly lower after caffeine, likely because the body’s reflexes responded to the higher blood pressure by slowing the heart. So a child drinking an energy drink won’t necessarily feel their heart racing, but the strain on their blood vessels is real.
Sleep Gets Worse in Several Ways
Sleep is where caffeine does some of its most visible damage in kids. Children who consume more caffeine sleep fewer total hours, have more restless nights, and wake up more tired in the morning. A study in the Journal of Clinical Sleep Medicine found that kids sleeping only 7 to 8 hours per night consumed significantly more caffeine than those sleeping the recommended 9 to 11 hours. Higher caffeine intake was linked to worse bedtime routines, more restless sleep, and greater morning tiredness.
The relationship works in both directions, creating a cycle that’s hard to break. A child drinks caffeine, sleeps poorly, wakes up tired, then reaches for more caffeine the next day. The study found that disrupted sleep routines and restless nights fully explained the connection between caffeine and morning tiredness, meaning caffeine’s effect on daytime alertness runs directly through worsened sleep.
The Developing Brain May Be Especially Vulnerable
During adolescence, the brain goes through a critical remodeling process. An overproduction of connections between brain cells peaks just before puberty, and then the brain spends the teenage years pruning away unnecessary connections to become more efficient. This pruning process is reflected in a specific pattern of deep sleep brain waves called slow wave activity.
Caffeine suppresses those deep sleep waves. Research from the University Children’s Hospital Zurich found that when adolescent rats were given caffeine for just five days around puberty, the normal pruning of brain connections was reduced. The caffeine-treated animals also showed less of the age-appropriate increase in exploratory behavior that typically comes with maturation. In other words, caffeine appeared to delay the brain’s developmental timeline during a window that doesn’t come back.
This is an animal study, and researchers can’t ethically replicate it in human children. But the underlying biology, deep sleep driving brain maturation, is well established in humans too. Because this pruning period is also associated with vulnerability to psychiatric and mood disorders, disrupting it with regular caffeine use raises concerns that go beyond a bad night’s sleep.
Behavioral and Emotional Side Effects
Caffeine doses between 100 and 400 mg produce increased nervousness, jitteriness, and fidgetiness in children and adolescents, with effects scaling up as the dose increases. In a survey of adolescent caffeine users, the most commonly reported problems were caffeine cravings, frequent urination, and difficulty falling asleep. About 7.5% reported trouble concentrating, and about 3% described feeling anxious, jittery, or nervous.
These numbers may seem low, but they reflect only the symptoms adolescents themselves recognized and attributed to caffeine. Caffeine can easily be an unrecognized contributor to concentration problems and anxiety in school-age kids, particularly when the child or parent doesn’t connect the dots between a morning soda and afternoon restlessness.
Temporary Insulin Resistance
One less obvious effect: caffeine temporarily changes how the body handles sugar. In a double-blind crossover study of adolescents aged 13 to 19, a single caffeinated energy shot (at a dose equivalent to one standard sugar-free energy shot) caused a 25% increase in blood sugar response and a 26% increase in insulin response compared to a decaffeinated version. Insulin sensitivity dropped significantly, meaning the body had to work harder to process the same amount of sugar.
This effect was acute and transient, not a permanent change. But for kids who drink caffeinated energy drinks regularly alongside sugary foods, it means their bodies are repeatedly pushed into a state of temporary insulin resistance. The study also found that teenagers who metabolize caffeine faster genetically experienced even greater glucose intolerance, suggesting the effect isn’t uniform across all kids.
Bone Health Appears Unaffected
One common concern that doesn’t hold up under scrutiny: caffeine weakening growing bones. While lab and animal studies have shown caffeine can interfere with calcium metabolism, a large observational and genetic analysis published in PLOS One found no meaningful relationship between caffeine intake and bone mineral density in children and adolescents. This held true across measurements at the hip, spine, and total body. Parents don’t need to worry that a child’s occasional caffeinated soda is softening their bones.
Withdrawal Hits Faster Than You’d Expect
Children who consume caffeine regularly can develop physical dependence. When they stop, withdrawal symptoms typically appear within 12 to 24 hours and peak between 20 and 48 hours. The classic symptoms are headache, fatigue, yawning, low mood, and anxiety.
In a study of school-age children, stopping caffeine caused a measurable decline in attention and reaction time on a visual performance test within 24 hours. That decline persisted for up to a week. For a child in school, a week of slower reaction times and impaired concentration is significant, and it can happen simply because they skipped their usual caffeinated drink over a weekend or school break.
How Much Caffeine Kids Actually Get
Kids don’t need to drink coffee to consume significant caffeine. A 16-ounce energy drink like NOS contains about 163 mg. An 8-ounce Rockstar contains 79 mg. A 12-ounce can of cola has roughly 35 to 45 mg. Even a single ounce of dark chocolate contains about 24 mg, and a cup of chocolate milk has around 2 mg.
Health Canada’s guideline, one of the few international bodies to set a specific number, recommends children under 12 consume no more than 2.5 mg of caffeine per kilogram of body weight per day. For a 60-pound (27 kg) child, that ceiling is about 68 mg, less than a single 8-ounce energy drink. For a 90-pound (41 kg) preteen, it’s roughly 100 mg. The American Academy of Pediatrics takes a simpler stance: kids should avoid caffeine altogether.
In practice, a child who drinks one energy drink has likely exceeded every major guideline in a single serving. Even two cans of cola in a day can push a smaller child past the threshold where blood pressure changes and sleep disruption become measurable.