Health Reference Library

Which supplements for anxiety have evidence?

This entry is part of the Nutri Tailor Health Reference Library — cited research on supplements, nutrients and adjacent areas of health.

Summary

Three options carry evidence for anxiety symptoms. Ashwagandha comes first, at 240 to 600 mg a day for eight weeks, with lower anxiety and stress scores and morning cortisol in two placebo-controlled trials. L-theanine at 200 mg lowered trait anxiety and improved sleep over four weeks. Magnesium showed benefit for subjective anxiety in a 2017 systematic review of low-quality trials, with the largest effect in people who are low. CBD, 5-HTP, kava and GABA capsules have weak, absent or unsafe evidence. Breathing practice and exercise have better evidence than any of these and cost nothing. Persistent anxiety, panic attacks or anxiety that stops ordinary functioning is a GP or talking-therapy matter, with supplements alongside rather than instead.

How it works

Ashwagandha acts on the stress axis, lowering cortisol and modulating GABA, which is why its trials measure both mood scores and a hormone and why it takes weeks. Theanine raises alpha-wave activity within an hour and takes the edge off the physiological stress response, so it suits the wired, racing-mind presentation and the poor sleep that comes with it. Magnesium is consumed by the stress response and low intake worsens the reactivity, which is the vicious-circle model described in the 2020 review; replacing it in someone who is low calms the loop, in someone replete it does little. None of these addresses the thoughts themselves, which is what therapy does, and which is why the evidence for breathing, exercise and CBT is stronger than for any capsule.

Timing

Theanine within an hour and over the first week; magnesium over two to four weeks where low; ashwagandha over six to eight weeks. Judge at eight weeks, one at a time.

Safety profile

Ashwagandha is avoided in pregnancy and breastfeeding, thyroid overactivity and liver disease, and reviewed with the GP on sedatives, thyroid or immunosuppressant prescriptions; rare liver reactions are reported. Kava carries liver toxicity warnings. 5-HTP is not combined with antidepressants. CBD products are unregulated in dose. Magnesium above 400 mg loosens bowels. Chest pain, breathlessness or panic attacks that are new, thoughts of self-harm, or anxiety that stops you working or leaving the house are GP or urgent matters, and 111 or 999 apply where there is risk. Nutri365 checks for interactions and contraindications before suggesting any of these and refers persistent anxiety to the GP.

Special populations

Anyone on an antidepressant, anxiolytic or sleeping tablet checks with the prescriber before any of these. Pregnancy excludes ashwagandha. Perimenopausal anxiety is often hormonal and is addressed on the [perimenopause page](/apps/learn/perimenopause-symptoms-and-what-actually-helps). Teenagers are a GP matter, not a supplement matter.

Guideline positions

Lopresti 2019, 60 adults, ashwagandha 240 mg for 60 days: reduced Hamilton Anxiety and DASS-21 scores and morning cortisol versus placebo. Salve 2019, 250 and 600 mg for eight weeks: reduced perceived stress and cortisol, better sleep. Hidese 2019, 200 mg L-theanine for four weeks, 30 adults, crossover: reduced trait anxiety, depression scale and sleep-quality scores. Boyle 2017, systematic review of magnesium and subjective anxiety: suggestive benefit, low-quality evidence. Pickering 2020 on the magnesium-stress vicious circle. Rawji 2024, magnesium and self-reported anxiety and depression: supportive, heterogeneous. NICE CG113 on generalised anxiety disorder puts psychological therapy and, where needed, prescription first; supplements are not part of the pathway.

Practical framework

The option is matched to the pattern. Where the pattern is chronic stress, wired-and-tired and poor sleep for months, ashwagandha runs at 300 to 600 mg a day for eight weeks, per the [ashwagandha page](/apps/learn/does-ashwagandha-work-for-stress-and-sleep-what-dose). Where it is acute, with a racing mind, difficulty switching off and sleep onset the problem, theanine runs at 200 mg, daily or before a known trigger, for four weeks, per the [theanine page](/apps/learn/does-theanine-help-with-stress-and-sleep-what-dose-did-the-trials-use). Where it is muscle tension, cramps, a low-fibre diet, heavy training and poor sleep depth, magnesium bisglycinate runs at 200 to 400 mg elemental in the evening, with the expected timeline on [magnesium for anxiety](/apps/learn/magnesium-for-anxiety-and-stress-what-timeline-to-expect). One runs at a time, and the free levers run underneath all of them, meaning the [breathing exercises with evidence](/apps/learn/breathing-exercises-for-anxiety-which-ones-have-evidence), daily movement, caffeine and alcohol down, and the fuller method on [how to reduce anxiety naturally](/apps/learn/how-to-reduce-anxiety-naturally-what-the-evidence-supports). Where anxiety is persistent or stops ordinary functioning, the GP and NHS talking therapies are the route, and the supplements sit alongside. Nutri365 reads whether the chosen option is moving sleep, resting heart rate and reported mood over eight weeks, checks for interactions and contraindications, and refers questions outside scope to a health specialist.

Common misconceptions

GABA capsules do not cross into the brain in meaningful amounts. CBD gummies at the doses sold are far below anything trialled. Magnesium helps people who are low, not everyone. And a supplement that helps anxiety symptoms is not addressing an anxiety disorder, which needs therapy or the GP.

Sources

  1. Lopresti AL, Smith SJ, Malvi H, Kodgule R 2019. An investigation into the stress-relieving and pharmacological actions of an ashwagandha extract. Medicine (Baltimore). PMID: 31517876
  2. Salve J, Pate S, Debnath K, Langade D 2019. Adaptogenic and Anxiolytic Effects of Ashwagandha Root Extract in Healthy Adults. Cureus. PMID: 32021735
  3. Hidese S, Ogawa S, Ota M, Ishida I, Yasukawa Z, Ozeki M, Kunugi H 2019. Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial. Nutrients. PMID: 31623400
  4. Boyle NB, Lawton C, Dye L 2017. The Effects of Magnesium Supplementation on Subjective Anxiety and Stress: A Systematic Review. Nutrients. PMID: 28445426
  5. Pickering G, Mazur A, Trousselard M, et al 2020. Magnesium Status and Stress: The Vicious Circle Concept Revisited. Nutrients. PMID: 33260549
  6. Rawji A, Peltier MR, Mourtzanakis K, et al 2024. Examining the Effects of Supplemental Magnesium on Self-Reported Anxiety and Sleep Quality. Cureus. PMID: 38817505

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