Yes, phosphatidylserine lowers cortisol. The clinical evidence is consistent on this point, and it is one of the few supplements where the mechanism is well understood rather than merely assumed. But I want to be precise from the outset, because the way this is usually explained online is misleading. Phosphatidylserine is not a cortisol blocker. It does not switch cortisol off. It is a phospholipid, a structural fat that sits within the membrane of every one of your cells, and its influence on cortisol comes from restoring the regulation of the system that produces it, rather than overriding that system. That distinction is not academic. It determines who this supplement helps, who it does not, and how you should think about using it. [2][5]
What is Phosphatidylserine?
Phosphatidylserine (PS) is a phospholipid found in the cell membranes of virtually every cell in the body, with the highest concentrations in the brain. It forms a critical structural component of neuronal membranes, where it regulates the behaviour of membrane-bound proteins, supports neurotransmitter release, and facilitates the signalling pathways that neurons depend on for communication and survival. [7]
In the brain, phosphatidylserine is particularly abundant in regions associated with memory, learning and the stress response. Its role is not passive: it actively supports the function of receptors, ion channels and signalling proteins within the neuronal membrane. DHA, the primary omega-3 fatty acid in the brain, and phosphatidylserine have a close interdependent relationship. DHA promotes the synthesis of phosphatidylserine in neuronal membranes, which is one of the reasons adequate omega-3 intake and phosphatidylserine supplementation are often considered together in brain health protocols. [7][9]
Phosphatidylserine declines with age, and this decline is associated with reduced cognitive performance, impaired stress regulation and increased vulnerability to mood disorders. It is worth noting that food sources of phosphatidylserine are limited in a modern diet: white beans, egg yolks and some organ meats contain modest amounts, but therapeutic levels are very difficult to achieve through diet alone.
A comprehensive review of phosphatidylserine and the human brain concluded that it is required for healthy nerve cell membranes and myelin, and that its supplementation is well absorbed, crosses the blood-brain barrier, and supports cognitive functioning across memory, learning, concentration and mood. [4]
How Does Phosphatidylserine Lower Cortisol?
The mechanism by which phosphatidylserine lowers cortisol is not direct suppression. It operates upstream, at the level of the hypothalamic-pituitary-adrenal (HPA) axis, the communication pathway between the brain and the adrenal glands that governs cortisol production. [8]
When the brain perceives a stressor, the hypothalamus releases corticotropin-releasing factor (CRF), which signals the pituitary gland to release ACTH (adrenocorticotropic hormone), which in turn signals the adrenal glands to produce cortisol. Phosphatidylserine appears to modulate this cascade at the pituitary level, reducing ACTH output and thereby reducing the downstream cortisol response. It does not block cortisol production entirely. What it does is blunt the exaggerated cortisol spike that occurs under acute stress, and over time, help normalise the dysregulated cortisol patterns associated with chronic stress.
I labour this point because it matters clinically. So much of the conversation around cortisol frames it as the enemy, a hormone to be crushed and eliminated. That is a fundamental misunderstanding. Cortisol is essential. It regulates blood sugar, modulates the immune system, controls inflammation and governs your energy across the day. A person with genuinely low cortisol is not well, they are exhausted. The goal is never suppression. It is regulation, and phosphatidylserine is one of the few compounds that supports regulation rather than blunt suppression. This is exactly why I reach for it in the situations I describe below, and why I leave it on the shelf in others. [5]
What Does the Clinical Evidence Show?
The most well-known study on phosphatidylserine and cortisol is a double-blind, placebo-controlled trial examining its effect on the hormonal response to moderate-intensity exercise. Ten healthy men supplemented with 600mg of phosphatidylserine daily for ten days using a crossover design. The result: phosphatidylserine significantly blunted the cortisol response before and during exercise-induced stress compared to placebo, while also favourably affecting the testosterone-to-cortisol ratio, a marker of physiological stress and recovery. [2]
A separate randomised, placebo-controlled trial examined the effect of a phosphatidylserine and phosphatidic acid complex on chronically stressed men exposed to a psychosocial stress test. The key finding was not simply that cortisol was lower, but that phosphatidylserine normalised the stress reactivity of the HPA axis. In subjects with elevated chronic stress, the blunting of the ACTH and cortisol response to acute stress was most pronounced. The supplement appeared to recalibrate the stress response system rather than simply suppress it. [5]
This finding, that phosphatidylserine recalibrates rather than simply suppresses, is the single most important thing to understand about it. It tells us the supplement works best precisely where it is needed most: in a system that has become overactive. In someone whose cortisol has already crashed, which I see often in the later stages of chronic stress, the case for phosphatidylserine as a cortisol intervention becomes much weaker. This is why I never prescribe it blindly for ‘stress’ as a catch-all. The pattern of cortisol dysregulation matters, and it is worth understanding yours before you supplement.
What Else Does Phosphatidylserine Do Beyond Cortisol?
The cortisol question is what most people search for, but it represents only one dimension of phosphatidylserine’s clinical value. Its broader roles in the brain are, in many ways, equally compelling. [9]
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Memory and cognitive function: Phosphatidylserine has been studied for its effects on age-related cognitive decline, with several trials showing improvements in working memory, verbal recall and attention in older adults. A 2025 randomised, double-blind, placebo-controlled trial in older adults with mild cognitive impairment found that phosphatidylserine supplementation significantly improved multiple domains of cognitive function over 12 months. [3]
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Neuroinflammation: Phosphatidylserine plays a role in the brain’s anti-inflammatory signalling. It is involved in the clearance of apoptotic cells and in modulating microglial activation, which is the brain’s primary immune response mechanism. Impaired PS metabolism has been associated with increased neuroinflammation.
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Neurotransmitter function: By maintaining neuronal membrane integrity, phosphatidylserine supports the function of receptors and ion channels involved in serotonin, dopamine and acetylcholine signalling. This is one of the reasons its effects extend beyond stress to mood, motivation and memory.
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Sleep quality: Phosphatidylserine’s role in cortisol regulation, particularly in blunting elevated evening cortisol, may indirectly support sleep quality in those who struggle to switch off at night. Elevated cortisol in the evening is one of the most common reasons people lie awake with a racing mind.
What Form of Phosphatidylserine Should You Take?
This matters more than most people realise, and there is a piece of history worth knowing. Much of the original and most impressive research on phosphatidylserine, including the landmark Monteleone study from 1992, used phosphatidylserine derived from bovine brain cortex. Then came the BSE crisis. In the 1990s, concerns about bovine spongiform encephalopathy led to brain-derived phosphatidylserine being withdrawn from the market entirely, and rightly so. This is relevant today because some of the strongest early evidence was generated using a form you can no longer buy.
Most phosphatidylserine supplements today are derived from soy lecithin or sunflower lecithin. The research on soy-derived PS, including the Hellhammer 2014 trial, supports its effectiveness for HPA axis modulation, and it is generally considered the evidence-based alternative. Sunflower-derived PS is increasingly available for those avoiding soy.
The doses used in cortisol-specific studies range from 400mg to 800mg per day, typically taken in divided doses. For cognitive support, doses of 100 to 300mg daily have also been studied. As always, quality matters: look for a supplement with a specified PS content rather than a broad phospholipid blend where PS may be present in minimal amounts.
How Does Phosphatidylserine Fit into a Broader Cortisol Protocol?
Phosphatidylserine is most useful as part of a considered approach to cortisol regulation rather than a standalone fix. The HPA axis is a complex system and its dysregulation rarely has a single cause or a single solution.
The supplements with the most complementary evidence for cortisol and HPA axis support include ashwagandha, which has 15 RCTs and a strong meta-analysis supporting significant cortisol reduction through direct HPA axis modulation, [1] and Rhodiola rosea, which supports stress resilience and mental fatigue through the catecholamine stress response. [6] Magnesium bisglycinate supports the HPA axis through its role in GABA receptor function and cortisol regulation, with the additional benefit that stress depletes magnesium rapidly, creating a reinforcing depletion cycle that supplementation can break. [10]
Where phosphatidylserine is most distinctively valuable within this combination is in its neurological role. While ashwagandha and Rhodiola work primarily on the physiological stress response, phosphatidylserine works at the level of neuronal membrane function, supporting the brain's capacity to regulate itself under stress. It is the most brain-specific of the cortisol-modulating supplements, and this is what makes it particularly relevant for those experiencing cognitive symptoms alongside elevated cortisol, such as poor working memory, brain fog, difficulty concentrating or trouble switching off at night.
For a deeper understanding of how cortisol dysregulation develops and what drives it, I have written a full guide on this topic: Adrenal Fatigue and Cortisol Supplements: What the Science Actually Says.
Who is Most Likely to Benefit?
This is where clinical judgement matters more than the marketing. In my experience, phosphatidylserine is not a supplement for everyone with stress, and giving it to the wrong person achieves very little. It is most useful, and I have seen it make a genuine difference, in a few specific situations:
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People under chronic psychological stress whose HPA axis is in a state of sustained overactivation, particularly those experiencing the cortisol-driven cognitive symptoms of brain fog, poor memory or sleep disturbance.
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Athletes and those doing high-intensity training, where exercise-induced cortisol spikes are a known driver of impaired recovery, mood and performance. The evidence for PS in this context is the most robust.
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Women in perimenopause, where HPA axis dysregulation often compounds the cognitive and mood effects of oestrogen decline. Phosphatidylserine’s dual role in cortisol regulation and cognitive support makes it particularly relevant during this transition.
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Those with age-related cognitive concerns, where the decline in brain PS levels contributes to reduced membrane function and neurotransmitter efficiency.
It is less likely to produce a dramatic cortisol-lowering effect in someone with already low cortisol, which is common in Stage 3 HPA axis exhaustion. In that context, the priority is rebuilding adrenal reserve rather than blunting further output.
Conclusion
So, can phosphatidylserine lower cortisol? Yes, and it does so intelligently, by helping the brain and adrenal glands communicate more appropriately rather than by force. That is precisely the kind of intervention I am drawn to as a practitioner: one that supports the body’s own regulatory capacity rather than overriding it.
What I value most about phosphatidylserine, though, is something the cortisol conversation tends to miss entirely. It works at the level of the neuronal membrane itself, supporting the physical structure your brain depends on to think clearly, regulate mood and hold a thought. Stress and brain fog almost always arrive together in the people I work with, and they are rarely two separate problems. They are the same problem expressed in two ways. A supplement that addresses both at once, upstream of the symptoms, is a genuinely useful tool. Phosphatidylserine is one of the few that does.
“The future of medicine will depend less on intervention, and more on how well we support the body’s own systems.” Marie Guerlain BSc NT, ND
Explore Rain Wellbeing
Sleep State by Rain Wellbeing contains phosphatidylserine alongside magnesium bisglycinate, Lion’s Mane, Reishi and NAC, formulated for deep, restorative sleep and overnight neurological recovery. Explore Sleep State. For stress resilience and cortisol support, Social State features ashwagandha KSM-66, Rhodiola rosea, L-Theanine and other adaptogens.
For more expert insights on stress, cortisol and functional wellbeing, visit the RAIN LAB and explore the Rain Wellbeing articles. [NOTE FOR UPLOAD: add internal blog link here]
Disclaimer
This article is intended for informational purposes only and does not constitute medical advice. The content reflects the author’s professional knowledge and the current state of published research, but should not be used as a substitute for consultation with a qualified healthcare professional. If you have a health condition or are taking medication, please seek guidance from your doctor or a registered practitioner before introducing any new supplement into your routine.
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