I recently read a Reddit thread where hundreds of people shared how they calm their nervous system. Walking in nature, boundaries, breathing, ice packs, essential oils, even psilocybin. Some of it is backed by solid research. Some of it is wishful thinking.
Here’s what the science actually says about how to reduce stress, calm your nervous system and lower cortisol, and when it makes sense to get tested.
How stress affects your body in 60 seconds
Your autonomic nervous system has two main modes:
Sympathetic: fight or flight. Heart rate up, digestion down, alert.
Parasympathetic: rest and digest. Heart rate slows, digestion and repair switch on. The vagus nerve is its main highway.
Alongside this runs your hormonal stress system, the HPA axis:
Your hypothalamus senses stress and releases CRH.
Your pituitary gland responds by releasing ACTH (adrenocorticotropic hormone).
ACTH tells your adrenal glands to make cortisol.
Cortisol then signals back to the brain to turn ACTH down. A built-in off switch.
Cortisol isn’t the enemy. It naturally peaks in the morning to get you going and falls towards bedtime. The problem is chronic stress, which can flatten this daily rhythm. A meta-analysis linked flatter cortisol slopes across the day with poorer mental and physical health outcomes.
The good news: you can influence both systems with simple daily habits.
1. Breathe slower and make the exhale longer
This is the fastest tool you have. A meta-analysis found that voluntary slow breathing (around 6 breaths per minute) raises heart rate variability, a key marker of parasympathetic activity.
In a Stanford trial, just 5 minutes a day of “cyclic sighing” (two inhales through the nose, then a long, slow exhale through the mouth) improved mood and lowered breathing rate more than mindfulness meditation over one month.
Try it: inhale for 4 seconds, exhale for 6 to 8. Five minutes, once or twice a day.
2. Use cold on your neck or face
The ice pack tip from Reddit isn’t nonsense. In a randomised controlled trial, cold applied to the neck area increased vagal (parasympathetic) activity and lowered heart rate. Splashing cold water on your face works on a similar reflex.
It’s a useful short-term tool. “0/10 anxiety every time” is overselling it.
3. Get outside for 20 to 30 minutes
The most upvoted answer in that thread was walking in nature, and it holds up. In a study of city dwellers, a 20 to 30 minute “nature pill” produced the biggest drop in salivary cortisol per minute spent. Leave the podcast at home if you can.
4. Move, but match the intensity to your stress load
Exercise at moderate to high intensity raises cortisol in the short term. That’s normal and part of how you adapt. But if you’re already exhausted, sleeping badly and running on coffee, daily HIIT may add load rather than relieve it.
Yoga, walking and steady movement consistently show lower cortisol and calmer physiology in research. A meta-analysis found yoga reduced evening cortisol, morning cortisol, heart rate and blood pressure.
5. Protect your sleep
Even one night of poor sleep raises cortisol the following evening, right when it should be falling. Regular bedtimes, morning daylight, and caffeine before midday make a real difference.
6. Eat in a way that steadies your body
Skipping breakfast, living on coffee and grabbing sugar at 4pm keeps your body in alert mode. Regular meals with protein, fibre and healthy fats help keep blood sugar steady, which means fewer stress signals. A Mediterranean-style pattern is an easy place to start (see my Mediterranean diet guide).
Since stress also shuts down digestion, bloating and irregular bowels are common when your nervous system is on high alert. More on that in Why Am I Always Bloated?
7. What about supplements?
Ashwagandha is the best studied. A 2022 meta-analysis found it reduced stress and anxiety scores, but the certainty of the evidence was rated low. It’s not suitable for everyone (for example, in pregnancy or with thyroid conditions), so check with a professional first. Supplements work best on top of the basics, not instead of them.
Mario's tip
Link a 2-minute breathing practice to something you already do every day: after you sit down at your desk, before lunch, and when you get into bed. Small and repeated beats long and occasional.
What about the other Reddit tips?
Boundaries and removing stressors: not a “hack,” but probably the most powerful long-term change.
Essential oils: pleasant and may help some people relax, but the evidence is mixed and small.
Psilocybin: being studied in clinical settings for depression. It’s not a DIY stress tool.
How to get your cortisol tested
If you’re constantly wired, exhausted, or can’t wind down despite doing the basics, testing can help.
Through your doctor:
Morning blood cortisol and ACTH (usually around 8 to 9am) as a first check.
If too much cortisol is suspected (Cushing’s syndrome): late-night saliva cortisol, 24-hour urine cortisol or a dexamethasone suppression test.
If too little is suspected (adrenal insufficiency): an ACTH stimulation test, which checks how well your adrenals respond.
ACTH and cortisol together tell your doctor whether a problem starts in the brain (pituitary) or the adrenal glands.
Functional testing: a salivary cortisol day profile (4 to 5 samples from morning to night) shows your daily rhythm. It’s not a diagnosis, but it can show patterns like a flat morning peak or high evening cortisol, which helps tailor your plan. For more on blood tests worth asking for, read Always Tired? 8 Nutritional Reasons for Low Energy.
See your GP promptly if you notice: unexplained weight gain around the face and belly, purple stretch marks, muscle weakness, dizziness on standing, salt cravings, or unexplained weight loss.
How I can help
Stress rarely shows up on its own. It sits behind poor sleep, low energy, gut issues, cravings and stubborn weight. In my practice I look at the full picture: what you eat, how you sleep, how you move and, where useful, what your cortisol rhythm actually looks like.
My 3-Month Health Optimisation Programme combines nutrition, lifestyle changes and practical breathwork from 15+ years of teaching yoga, with optional functional testing. In person in Barcelona or online, in English or German.
👉 Book a free call or message me on WhatsApp and let’s see where to start.
FAQ
What is the fastest way to reduce stress?
Slow breathing with a longer exhale is the fastest evidence-based tool. Try inhaling for 4 seconds and exhaling for 6 to 8 seconds for a few minutes, or use a "cyclic sigh": two inhales through the nose and one long exhale through the mouth. Cold water on the face or a cold pack on the neck can also calm your nervous system within minutes.
How do I activate my parasympathetic nervous system?
Slow breathing, time in nature, yoga, gentle movement, good sleep and regular meals all support parasympathetic activity. Research shows slow breathing increases heart rate variability, a key marker of a calmer nervous system. Consistency matters more than any single technique.
What is the connection between ACTH and cortisol?
ACTH is a hormone made by the pituitary gland in your brain. It tells your adrenal glands to produce cortisol. When cortisol rises, it signals back to the brain to lower ACTH. Doctors often test both together to find out whether a cortisol problem starts in the pituitary or the adrenal glands.
How can I lower cortisol naturally?
The best-supported approaches are regular sleep, slow breathing, yoga or other mind-body practices, 20 to 30 minutes outdoors, steady meals and moderate exercise. Ashwagandha has some evidence for reducing stress, but the research quality is still low, so check with a professional before taking it.
Which test measures cortisol?
Your doctor may use a morning blood test for cortisol and ACTH, a late-night saliva test, a 24-hour urine test, a dexamethasone suppression test or an ACTH stimulation test, depending on whether too much or too little cortisol is suspected. A salivary cortisol day profile can show your daily rhythm but is not used to diagnose disease.
View scientific references
Adam EK, Quinn ME, Tavernier R, McQuillan MT, Dahlke KA, Gilbert KE. Diurnal cortisol slopes and mental and physical health outcomes: A systematic review and meta-analysis . Psychoneuroendocrinology. 2017;83:25–41.
Akhgarjand C, Asoudeh F, Bagheri A, Kalantar Z, Vahabi Z, Shab-Bidar S, et al. Does Ashwagandha supplementation have a beneficial effect on the management of anxiety and stress? A systematic review and meta-analysis of randomized controlled trials . Phytotherapy Research. 2022;36(11):4115–4124.
Balban MY, Neri E, Kogon MM, Weed L, Nouriani B, Jo B, et al. Brief structured respiration practices enhance mood and reduce physiological arousal . Cell Reports Medicine. 2023;4(1):100895.
Bornstein SR, Allolio B, Arlt W, Barthel A, Don-Wauchope A, Hammer GD, et al. Diagnosis and treatment of primary adrenal insufficiency: An Endocrine Society clinical practice guideline . Journal of Clinical Endocrinology & Metabolism. 2016;101(2):364–389.
Hill EE, Zack E, Battaglini C, Viru M, Viru A, Hackney AC. Exercise and circulating cortisol levels: The intensity threshold effect . Journal of Endocrinological Investigation. 2008;31(7):587–591.
Hunter MR, Gillespie BW, Chen SY. Urban nature experiences reduce stress in the context of daily life based on salivary biomarkers . Frontiers in Psychology. 2019;10:722.
Jungmann M, Vencatachellum S, Van Ryckeghem D, Vögele C. Effects of cold stimulation on cardiac-vagal activation in healthy participants: Randomized controlled trial . JMIR Formative Research. 2018;2(2):e10257.
Laborde S, Allen MS, Borges U, Dosseville F, Hosang TJ, Iskra M, et al. Effects of voluntary slow breathing on heart rate and heart rate variability: A systematic review and a meta-analysis . Neuroscience & Biobehavioral Reviews. 2022;138:104711.
Leproult R, Copinschi G, Buxton O, Van Cauter E. Sleep loss results in an elevation of cortisol levels the next evening . Sleep. 1997;20(10):865–870.
Nieman LK, Biller BMK, Findling JW, Newell-Price J, Savage MO, Stewart PM, et al. The diagnosis of Cushing's syndrome: An Endocrine Society clinical practice guideline . Journal of Clinical Endocrinology & Metabolism. 2008;93(5):1526–1540.
Pascoe MC, Thompson DR, Ski CF. Yoga, mindfulness-based stress reduction and stress-related physiological measures: A meta-analysis . Psychoneuroendocrinology. 2017;86:152–168.
