By Jack Dell’Accio, Certified Sleep Coach, CEO & Founder of Essentia
For most of my career, I’ve talked about sleep in terms of recovery; how the body repairs itself, how inflammation is reduced, how muscles rebuild. But as we’ve continued to study sleep more deeply, especially through double-blind research, something became clear:
The mind and mental health are rebuilt at night just as much as the body.
In Essentia’s most recent double-blind sleep study with professional athletes, we were primarily tracking REM and Deep sleep. Those metrics matter—they’re where physical repair, memory consolidation, and nervous system recovery occur. But the most compelling outcomes weren’t only found in the data.
They were found in the people.
How We Measured Mental Health in the Sleep Study And What the Science Says
One of the most important aspects of this double-blind sleep study was that we didn’t rely on sleep data alone. REM and Deep sleep tell us what the brain is doing at night, but they don’t always tell us how that shows up in real life.
That’s why we paired objective sleep tracking with structured mental-health questionnaires designed to capture changes in perceived stress, emotional regulation, focus, mood stability, and overall happiness.
Every participant wore the same validated sleep-tracking device, allowing us to measure REM sleep, Deep sleep, and sleep continuity night after night. At the same time, we asked athletes, at two separate points during the 10-week study, to reflect on how they were actually functioning: emotionally, cognitively, and relationally.
The double-blind design was critical. Every athlete believed they were sleeping on an Essentia mattress. Only half actually were. The other half slept on premium non-Essentia mattresses representative of the broader market. This eliminated expectation bias and allowed us to observe what happens when sleep physiology truly changes, not just perception.
Early in the study, both groups reported feeling better. That’s normal. The brain responds quickly to novelty and expectation. But as the weeks progressed, a clear divergence appeared.
Only participants who showed sustained increases in REM and Deep sleep continued to report improvements in mood, emotional resilience, and mental clarity. When REM and Deep sleep did not improve or regressed, the initial positive feelings faded.
This pattern mirrors what clinical sleep science has been showing for years: emotional regulation is not restored by rest alone, but by specific stages of sleep that allow the brain to recalibrate stress responses and process emotional load.
The Results of the Questionnaire
This alignment between subjective experience and objective sleep data wasn’t surprising. It’s exactly what we see in the broader scientific literature.
Organizations like the Mayo Clinic describe sleep as a core regulator of emotional health, not just a period of rest. During REM sleep in particular, communication between the amygdala and the prefrontal cortex, the brain’s emotional control system, is recalibrated. When REM sleep is shortened or fragmented, emotional reactivity increases while stress tolerance drops.
Research from Stanford Medicine further reinforces this connection, showing that insufficient or disrupted sleep increases vulnerability to anxiety and depressive symptoms while reducing emotional control and cognitive flexibility.
Large-scale meta-analyses now suggest something even more important: improving sleep quality doesn’t just correlate with better mental health, it actively contributes to reductions in stress, anxiety, and mood disturbance. The more consistently REM and Deep sleep are restored, the greater the mental-health benefit.
So when athletes reported feeling calmer, more focused, less irritable, and emotionally steadier, and those reports tracked directly with increases in REM and Deep sleep, we weren’t seeing anecdotes.
We were seeing biology behave exactly as it’s designed to.
Sleep stabilizes the mind as much as it restores the body.
The Outcome That Data Alone Can’t Explain
By the end of the study, 96 percent of participants who achieved consistent improvements in REM and Deep sleep reported clear, measurable improvements in mental well-being.
These weren’t vague impressions. They were specific, repeated observations:
- Sharper mental clarity
- Improved ability to retain coaching instructions and video reviews
- Greater focus under pressure
- Faster emotional recovery after mistakes
- A noticeable increase in perceived happiness
- Reduced stress and irritability
What stood out to me most was how relational these changes were. Athletes described better communication with teammates and coaches, less emotional reactivity, and a calmer presence in high-pressure situations.
That matters because irritability is often the earliest sign of compromised sleep. And when irritability increases, relationships tend to be the first thing to break down.
A great relationship, whether with a partner, a teammate, or a coach, almost always starts with great sleep.
REM and Deep Sleep Don’t Just Restore the Body, They Stabilize the Mind
When REM and Deep sleep are protected, the brain does what it’s designed to do:
- Emotional processing becomes cleaner
- Stress responses soften
- The nervous system recalibrates
- Information is absorbed instead of resisted
This isn’t mindset coaching.
This isn’t positive thinking.
This is biology functioning as intended once sleep stops getting in the way.
When sleep quality improves, the brain no longer has to operate in survival mode. It can regulate emotions naturally, filter stress more effectively, and show up present instead of reactive. That’s why mental clarity, emotional resilience, and perceived happiness consistently rise alongside REM and Deep sleep.
When Sleep Is Compromised, the Brain Never Resets
I recently discussed this on the Homes That Heal podcast with Jen Heller, where we explored how deeply sleep environment affects mental health—sometimes in ways people don’t recognize until they finally experience true recovery.
What struck me about that conversation wasn’t just the story itself, but the pattern it revealed.
When someone is chronically underslept or trapped in fragmented sleep:
- Stress carries over from one day to the next
- Emotional weight accumulates instead of clearing
- The nervous system never feels safe enough to reset
Sleep is supposed to be the reset.
When it fails, everything stacks.
And over time, that stacking shows up as anxiety, irritability, emotional exhaustion, and disconnection; not because someone is broken, but because their brain never gets the conditions it needs to recover.
Why Sleep Is the Foundation, Not the Finish Line
Sleep doesn’t replace therapy.
It doesn’t solve trauma.
It doesn’t eliminate life’s challenges.
But without sleep, none of those things can work properly.
When sleep quality improves, something important happens: The brain declutters.
That clarity creates space for reflection, communication, emotional processing, and healing. The real work still happens while awake, but sleep makes that work possible.
This is why we see mental health improvements across such a wide range of people, from elite athletes to individuals navigating significant life stress. The circumstances differ, but the mechanism is the same.
Protect REM. Protect Deep sleep.
And the mind becomes more resilient.
Why Duration Matters Less Than Depth
One of the biggest myths in sleep is that everyone needs the same number of hours.
What matters far more is how efficiently someone reaches REM and Deep sleep.
We’ve seen high performers achieve over three hours of combined REM and Deep sleep in under six hours total. Others may need longer periods initially to repay sleep debt or stabilize their nervous system.
That’s normal.
Sleep needs change as the body heals.
What matters is that the sleep being achieved is restorative—because without REM and Deep sleep, eight hours means nothing.
Mental Health Isn’t Separate From Sleep. It’s Built Inside It
If there’s one takeaway from this entire Rest. Repair. Regenerate. series, it’s this:
Sleep isn’t passive.
It’s not downtime.
It’s not optional.
It’s when the brain does the work it cannot do while awake.
REM sleep clears emotional residue.
Deep sleep stabilizes the nervous system.
Together, they restore the mind’s ability to regulate, adapt, and connect.
When sleep is protected—when the environment is supportive, non-toxic, and designed to minimize disruption—the brain finally gets out of its own way.
And when that happens, people don’t just perform better.
They feel better.
They relate better.
They live better.
That’s not philosophy.
That’s physiology.
Be well,
Jack
