The short version
- A 2017 systematic review of 18 magnesium studies found positive effects on subjective anxiety in four of eight trials in anxious samples, four of seven in premenstrual syndrome samples, one of two in hypertensive samples, and none in postpartum women.
- That review found no study had administered a validated measure of subjective stress as an outcome, and concluded the existing evidence is poor quality and that well-designed randomised controlled trials are required.
- A separate 2017 review of supplements and stress in women found magnesium reduced premenstrual anxiety only in combination with vitamin B6, with no effect used in isolation.
- The largest magnesium-for-stress trial randomised 264 stressed adults with low serum magnesium to magnesium plus B6 or magnesium alone for eight weeks; stress scores fell 44.9% and 42.4% respectively, but the trial had no placebo arm at all.
- The widely cited magnesium-and-stress vicious circle review was written in part by employees of and consultants to the pharmaceutical company that sponsored that trial and markets the product used in it.
We sell a magnesium glycinate. Here is the review literature on magnesium and anxiety, in the order it was published, with nothing removed.
2017: suggestive, and poor quality
Boyle, Lawton and Dye at the University of Leeds systematically reviewed interventions using magnesium alone or in combination. Eighteen studies met criteria. Every one of them recruited samples with an existing vulnerability to anxiety: mildly anxious people, women with premenstrual syndrome, postpartum women, people with hypertension.
The tally: four of eight studies in anxious samples reported positive effects on subjective anxiety. Four of seven in PMS samples. One of two in hypertensive samples. Magnesium had no effect on postpartum anxiety.
And then the finding that should end most magnesium-for-stress marketing on the spot. No study administered a validated measure of subjective stress as an outcome. Not one, in a review specifically searching for magnesium's effect on anxiety and stress. The reviewers' conclusion was that the existing evidence is suggestive of a beneficial effect in anxiety-vulnerable samples, that its quality is poor, and that well-designed randomised controlled trials are required.
2017 again, from a different institute
The Joanna Briggs Institute in Adelaide reviewed supplements and stress in women the same year. Fourteen studies. On magnesium specifically: combined magnesium and vitamin B6 reduced premenstrual anxiety, but magnesium had no effect when used in isolation, and did not affect stress in women with dysmenorrhoea either combined or alone.
Two independent teams, same year, same cautious landing.
2018: the biggest trial, and the missing arm
Pouteau and colleagues published the largest study of magnesium for stress in PLoS One. Two hundred and sixty-four healthy adults with a DASS-42 stress subscale score above 18 and serum magnesium between 0.45 and 0.85 mmol/L, randomised 1:1 to magnesium plus vitamin B6 (300mg and 30mg) or magnesium alone (300mg), for eight weeks.
Both arms improved substantially: stress scores fell 44.9% on the combination and 42.4% on magnesium alone, with no statistical difference between them. A pre-specified subgroup with severe or extremely severe stress (score ≥25, n = 162) did 24% better on the combination — 3.16 points, 95% CI 0.50 to 5.82, p = 0.0203.
Now the structural problem. There was no placebo arm. Everyone in this trial received magnesium. So a 44% improvement over eight weeks is uninterpretable as evidence that magnesium did anything, because there is no group who did not take it. Given that the properly controlled stress literature routinely shows large placebo responses, that 44% figure — which does circulate on its own — should not be treated as a magnesium effect. Several of the authors were employees of the company that markets the combination product.
2020: the mechanism, and who wrote it
The story you will hear is the vicious circle: stress increases magnesium loss, magnesium deficiency increases susceptibility to stress, round and round. A 2020 review in Nutrients revisited that concept, first proposed in the early 1990s, and it is the paper most often cited for it.
The mechanism is plausible and the review is a legitimate piece of work. It is also worth knowing that several of its authors are employees of, or consultants to, the same pharmaceutical company that sponsored the trial above and sells the magnesium product used in it. That does not make the hypothesis wrong. It makes it a hypothesis being advanced by a party with an interest in it, and you should weight it accordingly — as we would want you to weight anything we publish about our own products.
What we'd actually tell you
Buy magnesium if your intake is likely low. That is a defensible reason on its own and it has nothing to do with anxiety — plenty of people do not hit the recommended intake from food, glycinate is well tolerated, and correcting a shortfall is worth doing for reasons unrelated to how you feel.
Do not buy it as an anxiety product. The strongest honest sentence the literature supports is: suggestive, in people who were already anxious, on measures that in most cases were not validated for stress, from trials the reviewers themselves called poor quality. Nine years and several reviews later, the well-designed trial they all asked for still has not been run.
If anxiety is the actual problem, two things are worth more than a capsule. The first is a doctor, because persistent anxiety is treatable and a mineral is not the treatment. The second is slow breathing, which has pooled randomised data with control groups and costs nothing — and which we would rather you tried before our shelf. If you want something in a bottle with a tighter evidence story for an acute moment, l-theanine is honest about being an attention effect measured in hours, which is at least a claim someone has tested properly.
Good questions
Does magnesium help with anxiety?
The honest answer is that the evidence is suggestive and poor quality. Systematic reviews found roughly half the trials in already-anxious samples positive, none using a validated stress measure, and every review since 2017 has called for the well-designed trial that still has not been run. If a brand tells you magnesium fixes anxiety, they are describing marketing.
How much magnesium is used in the stress research?
300mg a day of elemental magnesium is the dose in the largest trial, taken for eight weeks. That trial gave magnesium to everyone and had no placebo group, so the dose is well documented while the effect is not. Recommended daily intakes for adults sit in a similar range, which is one reason correcting a dietary shortfall is a more defensible purchase.
Should I take magnesium with vitamin B6 for stress?
The evidence for the combination beating magnesium alone is limited to one pre-specified subgroup. In the full trial population there was no statistical difference between the two arms. Only among participants with severe or extremely severe stress did the combination do 24% better. That is a subgroup finding from an unblinded, placebo-free trial.
Is there any reason to take magnesium at all?
Yes, and it is not about anxiety. Many people do not reach recommended magnesium intake from food, glycinate is well tolerated compared with cheaper forms, and correcting a genuine dietary shortfall is worth doing on its own terms. Buy it for that reason and any effect on how you feel is a bonus rather than the premise.
Why does every article say magnesium is calming if the trials are weak?
Because the mechanism story is elegant and heavily promoted. Magnesium does have real roles in the regulation of the stress response, and the vicious circle hypothesis is plausible. But a plausible mechanism is not a demonstrated outcome, and the review most often cited for that mechanism was written partly by people employed by a company selling the product.
Sources
- Boyle NB, Lawton C, Dye L. The Effects of Magnesium Supplementation on Subjective Anxiety and Stress-A Systematic Review. Nutrients, 2017. View study
- McCabe D, Lisy K, Lockwood C, Colbeck M. The impact of essential fatty acid, B vitamins, vitamin C, magnesium and zinc supplementation on stress levels in women: a systematic review. JBI Database System Rev Implement Rep, 2017. View study
- Pouteau E, Kabir-Ahmadi M, Noah L, et al. Superiority of magnesium and vitamin B6 over magnesium alone on severe stress in healthy adults with low magnesemia: A randomized, single-blind clinical trial. PLoS One, 2018. View study
- Pickering G, Mazur A, Trousselard M, et al. Magnesium Status and Stress: The Vicious Circle Concept Revisited. Nutrients, 2020. View study
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
