The Hidden Risks of Long-Term Melatonin Use: What Emerging Science Suggests About Sleep Health & Hormone Safety

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The Hidden Risks of Long-Term Melatonin Use: What Emerging Science Suggests About Sleep Health & Hormone Safety

Published by Nature’s Bloom CBD

Edited & Reviewed by Nate Baker, Founder

For years, melatonin has been seen as the friendly, harmless answer to sleepless nights — a tiny pill promising rest in a restless world. Walk into almost any pharmacy, vitamin shop, or grocery store and you’ll find rows of melatonin in cheerful bottles, marketed as gentle, natural sleep support. Many people use it nightly without hesitation. Some parents keep it in the medicine cabinet for their children. Travelers rely on it for jet lag. Night-shift employees lean on it to reset their clocks. In America especially, melatonin has become less of a supplement and more of a routine.

But recent scientific attention is prompting a shift in how we think about this hormone. New research presented at the American Heart Association’s Scientific Sessions in 2025 has sparked a deeper conversation: could chronic melatonin use carry risks we’ve overlooked? While the study does not prove that melatonin causes cardiovascular problems, the association observed between long-term melatonin use and certain heart-related outcomes has researchers urging caution — and many consumers rethinking their nighttime habits.

This is not fear-mongering, and it is not anti-melatonin sentiment. Melatonin can absolutely have a role in sleep health. But like any hormone used regularly, understanding its effects — short-term, long-term, and systemic — matters. And right now, the popularity of melatonin is far ahead of the research on sustained use.

How Melatonin Became a Bedtime Mainstay

The rise of melatonin is tied to several cultural shifts:

• Increasing sleep challenges linked to stress, screens, and irregular schedules
• Growing distrust of prescription sleep medications
• A perception that “natural” equals safe
• An immense supplement market with low regulatory friction
• Digital lifestyle habits that push bedtimes later but demand mornings remain early

Many people don’t think of melatonin as a hormone — they think of it as a vitamin-like wellness tool. Yet melatonin is not a nutrient. It is a neurohormone with biochemical influence far beyond sleep timing.

In fact, studies have found that many melatonin supplements contain significantly more melatonin than their labels list — sometimes as much as** 4–5 times higher** (Erland & Saxena, 2017). Imagine taking unstandardized thyroid hormone or cortisol nightly — most people wouldn’t, because hormone modulation deserves precision.

With melatonin, however, that nuance often gets lost.

What the New Research Shows

The American Heart Association-referenced study examined electronic health records from over 130,000 adults diagnosed with chronic insomnia and tracked them for five years. Researchers compared long-term melatonin users to matched individuals who did not use melatonin.

The data revealed that those who used melatonin consistently for a year or longer had:

• A significantly higher likelihood of developing heart failure
• Higher rates of hospitalization associated with heart failure
• A notable increase in all-cause mortality

Researchers emphasized a key distinction: correlation, not causation. These findings do not prove melatonin causes harm — but they do raise safety questions about long-term hormone supplementation without clinical oversight.

Medicine evolves by paying attention when patterns appear, and this pattern deserves attention.

Why Hormones Demand Respect — Even “Natural” Ones

Melatonin is involved in more than falling asleep. It interacts with:

• Immune system regulation
• Cardiovascular signaling
• Antioxidant pathways
• Blood pressure modulation
• Mitochondrial balance
• Endocrine feedback loops

Chronic input of a hormone may influence pathways that extend far beyond bedtime. In pharmacology, we treat hormones with caution because they are signaling messengers, not passive molecules.

The misconception that melatonin is simply a natural sleep vitamin has encouraged a casualness around long-term consumption that many researchers now believe may be premature.

Most Sleep Struggles Aren’t Melatonin Problems

Melatonin is effective when sleep timing is off — not necessarily when sleep stress is high.

It is best supported for:

• Jet lag
• Shift work
• Delayed sleep-phase cycles
• Circadian disruption

But most modern insomnia stems from:

• Stress-driven cortisol disruption
• Screen exposure delaying natural melatonin release
• Blue light suppressing sleep cues
• Anxiety states activating alertness circuits
• Irregular routines
• Overstimulation before bed
• Poor sleep hygiene

In these situations, adding melatonin doesn’t address the underlying biology — it simply overlays a hormonal signal onto a dysregulated system.

A sleep specialist recently compared melatonin to turning up a car’s GPS volume when you’re lost — louder directions don’t fix wrong turns. You need to reset your route, not just amplify the signal.

The Nervous System, Not Melatonin, Drives Most Sleep Transitions

Modern sleep science increasingly emphasizes the autonomic nervous system — specifically the shift into parasympathetic dominance (“rest-and-digest”).

When the mind and body remain in alert mode, sleep onset is delayed regardless of melatonin levels. Supportive research is expanding into:

• Breathwork to stimulate vagal tone
• Temperature therapy (warm bath → cool bedroom)
• Evening light modification
• Sensory wind-down routines
• Magnesium and mineral balance
• Herbal relaxation support
• Gentle plant-based compounds including hemp-derived molecules being studied for relaxing effects on sleep-related pathways

No claims — just where the science is exploring.

In this paradigm, melatonin is not the villain — it’s simply not the universal sleep solution many assume.

Short-Term? Likely Fine. Long-Term? More Questions Ahead.

Experts agree that melatonin can be a helpful temporary support tool when used carefully. But sustained daily use without professional evaluation raises unknowns.

Dr. Marie-Pierre St-Onge, a leading sleep researcher involved in related commentary, notes that melatonin “is not indicated for chronic use in insomnia” in the United States.

That distinction matters.
Nightly melatonin habits may be more about habit and hope than evidence.

A Better Framework for Sleep Support

A more science-aligned approach to sleep support involves:

• Stabilizing light exposure cycles
• Maintaining regular sleep and wake times
• Reducing blue light in the evening
• Prioritizing stress-management routines
• Allowing enough wind-down time
• Supporting parasympathetic activation
• Considering gentle, non-hormonal options when needed

These practices build sleep resilience. They don’t try to “force” sleep — they help the brain ease into it.

This doesn’t mean melatonin is bad. It means melatonin may be misused, and potentially over-relied on, in ways that bypass deeper sleep health habits.

A Cultural Moment for Rethinking Sleep

We are in a transition point for sleep wellness — from quick fixes toward scientific precision.

Rather than asking:

What pill can make me sleep tonight?

The future of sleep asks:

How can I support the systems that make my body want to sleep naturally?

The exciting part? The momentum behind nervous-system-first sleep science is growing fast. And unlike hormone-based approaches, this pathway aligns with sustainability — physically and behaviorally.

Further Reading

For a detailed breakdown of the emerging melatonin data and safety discussions, visit:

👉 New Study Links Long-Term Melatonin Use to Higher Heart-Failure Risk
https://www.naturesbloom.net/blogs/news/new-study-links-long-term-melatonin-use-to-higher-heart-failure-risk-2025

References

American Heart Association. (2025). Long-term use of melatonin supplements to support sleep may have negative health effects.

Centers for Disease Control and Prevention. (2023). Sleep and chronic disease.

Erland, L. A., & Saxena, P. (2017). Melatonin content variability in supplements. Journal of Clinical Sleep Medicine.

National Institutes of Health. (2024). Sleep health and circadian biology.

Reiter, R., Sharma, R., et al. (2020). Melatonin and cardiovascular physiology. Cardiovascular Research.