For decades, melatonin has been the go-to supplement for anyone desperate for a good night’s sleep. Marketed as “natural,” “gentle,” and “non-addictive,” it became the feel-good answer to restless nights, glowing screens, and a society that never really stops moving. But new research has cast a long shadow over this popular sleep aid. Scientists have discovered a link between long-term melatonin use and a significantly higher risk of heart failure and the revelation is forcing many to rethink how they use it.
The Study That Started It All
At the 2025 American Heart Association’s Scientific Sessions in New Orleans, researchers presented one of the largest studies ever conducted on melatonin use. Led by Dr. Ekenedilichukwu Nnadi of SUNY Downstate/Kings County Primary Care in Brooklyn, the research team analyzed data from more than 130,000 adults diagnosed with chronic insomnia.
The participants, with an average age of 55, were split into two groups: those who had used melatonin for at least a year and those who had never used it at all. Over a five-year follow-up period, the differences were striking.
People who used melatonin for at least 12 months had about a 90 percent higher chance of developing heart failure compared to those who did not. They were also 3.5 times more likely to be hospitalized for heart failure and nearly twice as likely to die from any cause during that period.
That sounds frightening, but Dr. Nnadi himself was quick to clarify: correlation is not causation. “Our study shows an association, not proof that melatonin itself causes harm,” he explained. “Still, it raises important questions about how this supplement interacts with the heart over time.”
In other words, the data show a pattern worth paying attention to, but they don’t necessarily prove that melatonin is the culprit.
Why Experts Urge Caution, Not Panic
Sleep specialists and cardiologists across the United States have responded to the findings with both curiosity and caution. Christopher Winter, MD, a neurologist and sleep expert in Virginia, says the results are a reminder of how complex the relationship between sleep and heart health truly is.
“People who take melatonin long-term often do so because they already have chronic sleep problems,” he explains. “Poor sleep itself is one of the strongest risk factors for cardiovascular disease.”
This means melatonin users might already be at higher risk because of the very condition they are trying to treat. Shift workers, people with anxiety, and those living under chronic stress are all more likely to have both insomnia and heart issues.
Dr. Cheng-Han Chen, a cardiologist at MemorialCare Saddleback Medical Center in California, agrees. “Poor sleep quality is strongly linked with heart disease,” he said. “So if someone is relying on melatonin every night, it may simply reflect an underlying issue that’s already straining their heart.”
The heart and the sleep cycle are deeply intertwined. During deep sleep, blood pressure drops, heart rate slows, and the body repairs itself. When sleep is disrupted, this restorative process is cut short. Over time, that can contribute to hypertension, inflammation, and ultimately heart failure.
Melatonin: The Body’s Natural Night Signal
To understand how melatonin could be linked to heart health, it helps to revisit what the hormone actually does. Melatonin is produced naturally by the pineal gland, a small structure in the brain that releases it in response to darkness. Its rise and fall throughout the day regulates our circadian rhythm the body’s internal clock that dictates when we feel sleepy or alert.
In a perfect world, melatonin levels surge after sunset, helping us wind down, and drop again in the morning as light cues the body to wake. But modern life has disrupted this delicate rhythm. Blue light from phones, tablets, and late-night emails keeps our brains wired well past bedtime. As a result, many people turn to melatonin supplements to “reset” their internal clocks.
Here’s the catch: the doses found in most supplements are far higher than what the body naturally produces. While the pineal gland makes melatonin in microgram quantities, supplements often contain 3 to 10 milligrams hundreds of times more than what’s physiologically typical.
“Most people are taking way more melatonin than they need,” says Dr. Jamie Alan, a pharmacology professor at Michigan State University. “An effective dose for some adults can be as low as half a milligram.”
Because melatonin is considered a dietary supplement in the United States, it isn’t regulated by the Food and Drug Administration in the same way prescription drugs are. Independent testing has found that the actual amount of melatonin in pills and gummies can vary widely sometimes by as much as 400 percent. That lack of consistency adds yet another layer of uncertainty to the long-term safety of the supplement.
The Problem With “Natural”
Part of melatonin’s popularity comes from its image as a “natural” sleep aid. The logic seems simple: if it’s something your body already produces, how could it be harmful? But as doctors point out, “natural” doesn’t always mean “safe.”
Arsenic, lead, and hemlock are all natural, too and nobody’s rushing to take those at bedtime.
“People tend to assume that natural equals harmless, and that’s just not true,” Dr. Winter says. “Hormones are powerful substances. When you take them in amounts your body isn’t used to, you’re tinkering with a finely tuned system.”
Melatonin doesn’t just regulate sleep. It also influences body temperature, metabolism, immune function, and even blood pressure. Too much of it, or taking it at the wrong time of day, may interfere with these processes. Some scientists believe that chronic overuse could desynchronize the heart’s internal rhythm, leading to subtle stress on the cardiovascular system.
These theories are still under investigation, but they align with what’s already known about the heart’s dependence on regular sleep patterns.
A Society Out of Sync
The surge in melatonin use over the past two decades may say as much about modern life as it does about biology. According to the National Institutes of Health, melatonin use among U.S. adults quintupled between 1999 and 2018. Today, more than five million Americans say they take it regularly.
The rise mirrors an equally sharp increase in insomnia and other sleep disorders. The American Academy of Sleep Medicine estimates that up to 30 percent of adults struggle with chronic sleep issues, while nearly half report poor sleep quality on a weekly basis.
Artificial lighting, late-night work schedules, and constant digital stimulation have eroded the natural rhythm of day and night. Our brains no longer get the darkness cues that signal it’s time to rest. The result is a global sleep crisis and melatonin, once a niche supplement, has become a cultural crutch.
But experts warn that depending on it too heavily may only deepen the problem.
“Melatonin can be useful for short-term issues like jet lag or shift work,” says Dr. Chen. “But using it every night for years could mean you’re masking the root cause of poor sleep instead of addressing it.”
That cause could be anything from stress and anxiety to undiagnosed conditions like sleep apnea, which is itself a major cardiovascular risk factor.
Rethinking the Bedtime Routine
If melatonin isn’t the answer for chronic insomnia, what is? Sleep experts agree on one thing: the most powerful sleep aid doesn’t come in a bottle.
Dr. Nnadi and his colleagues recommend what’s known as “sleep hygiene,” a set of behavioral strategies proven to improve sleep naturally. These include maintaining a consistent bedtime, avoiding caffeine and alcohol before bed, limiting screen exposure in the evening, and creating a calm, dark sleep environment.
Cognitive behavioral therapy for insomnia (CBT-I) has also been shown to outperform both melatonin and prescription sleep drugs in long-term studies. The therapy works by changing the thoughts and behaviors that perpetuate insomnia teaching people to trust their own natural sleep patterns again.
Exposure to natural light during the day can help, too. Daylight signals the body to suppress melatonin in the morning, while the gradual dimming of light in the evening triggers its release. Reconnecting with these cycles helps the body regulate sleep more effectively. As Dr. Winter puts it, “Sleep is not a switch you flip. It’s a rhythm you align with.”
When the Heart and Sleep Fall Out of Sync
The connection between sleep and cardiovascular health has been well established for years. The American Heart Association even includes sleep as one of its “Essential 8” factors for preventing heart disease, alongside exercise, diet, and cholesterol management.
During sleep, the heart slows its pace, blood pressure drops, and inflammation subsides. This nightly rest period allows the cardiovascular system to recover from the day’s workload. Chronic insomnia disrupts that process. When the heart never gets a break, it operates under constant strain.
A 2024 study published in Frontiers found that people who regularly go to bed after midnight have a significantly higher risk of heart attack compared to those who sleep earlier. The researchers concluded that not only sleep quantity but also timing matters.
Melatonin sits at the center of this biological orchestra. It tells every cell in the body that night has arrived and that it’s time to rest. But when we override the system with artificial melatonin, we may inadvertently throw other hormonal and cardiovascular rhythms out of balance. It’s a reminder that sleep and heart health are not separate issues, but parts of the same ecosystem.
Respect the Rhythm
In the end, the message from scientists isn’t to fear melatonin, but to respect it. The hormone itself is not the villain misuse is. For short-term sleep disruptions, low-dose melatonin used under medical guidance is considered safe. The trouble begins when it becomes a nightly habit without understanding what’s really causing the problem.
The body’s sleep cycle is a symphony of hormones, light signals, and temperature changes, all tuned to the rising and setting of the sun. When we fall out of sync with that rhythm, we don’t just lose sleep we lose balance.
Our obsession with productivity, technology, and constant stimulation has turned rest into an afterthought. Melatonin has become a chemical shortcut to fix what is, at its core, a cultural and behavioral issue.
Listening to What Sleep Is Telling Us
The discovery that long-term melatonin use may increase the risk of heart failure is a wake-up call, not a panic button. It reminds us that the body is a complex, interconnected system. The heart, the brain, and the pineal gland all communicate through rhythm and timing. When we interfere with that natural timing even with something as seemingly harmless as a supplement there can be ripple effects.
Melatonin itself isn’t the enemy. It’s a messenger, a signal of darkness and restoration. The real danger lies in how we use it, or perhaps in what our reliance on it reveals about our lives.
Instead of chasing sleep through chemistry, experts urge us to rebuild a relationship with the natural cues that have guided humans for millennia. Dim the lights. Power down the screens. Let the body rediscover its rhythm.
In doing so, we might not only protect our hearts but also rediscover something deeper: the quiet intelligence of rest itself. Sleep, in the end, is not something we achieve. It’s something we allow when we finally stop trying so hard to control it.
