Many people turn to melatonin as a natural solution for restless nights — a small pill that promises deep sleep without the grogginess of stronger medications.
But new research suggests that long-term use of the supplement might not be as harmless as it seems.
A closer look at a “natural” remedy
Melatonin, a hormone produced naturally by the brain’s pineal gland, helps regulate the body’s sleep-wake cycle.
When night falls, melatonin levels rise, signaling the body that it’s time to rest. Synthetic versions of the hormone are widely available over the counter and are commonly used to treat insomnia and jet lag.
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Yet, despite its popularity, scientists have raised questions about the long-term safety of melatonin — especially when taken daily over many months or years.
Now, a new analysis from researchers working with the American Heart Association (AHA) offers a warning that’s difficult to ignore.
When good sleep comes at a cost
The study, which will be presented at the AHA’s 2025 Scientific Sessions in New Orleans, analyzed health data from thousands of adults with chronic insomnia.
Using a massive international database, the team compared people who had taken melatonin for at least a year with those who had never used it.
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The results were troubling. Over a five-year period, participants with long-term melatonin use had nearly double the risk of developing heart failure compared to non-users.
They were also more likely to be hospitalized for heart-related complications and had a higher overall mortality rate.
To put it simply, melatonin users faced:
- A 90% higher risk of developing heart failure
- A 3.5 times greater chance of being hospitalized due to heart failure
- Nearly twice the likelihood of dying from any cause during the study period
Why the risk may be higher
Researchers believe several factors could explain the connection. People with severe insomnia or underlying mental health conditions, such as anxiety or depression, may already be at greater cardiovascular risk — and they’re also more likely to use melatonin regularly.
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Still, even after accounting for these factors, the association between melatonin and heart problems remained strong.
The findings are especially important because melatonin is considered a dietary supplement in countries like the U.S., meaning it’s not regulated for safety or dosage consistency.
Pills from different brands can vary significantly in strength and purity — a detail that could make long-term use riskier than most consumers realize.
What this means for sleep and heart health
The researchers behind the study emphasize that melatonin may be safe for short-term use or for specific cases like jet lag.
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But they caution against chronic, unsupervised use — particularly for individuals with pre-existing heart conditions or poor cardiovascular health.
The takeaway is clear: even “natural” supplements can have unexpected effects on the body.
For those struggling with insomnia, doctors recommend focusing on non-drug strategies first — such as improving sleep hygiene, managing stress, and setting consistent sleep schedules — before turning to supplements or medication.
Article based on information from:
News Medical
TriNetX Global Research Network
Centers for Disease Control and Prevention – Sleep and Heart Health
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