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Limited evidenceStress & mood

Xiao Yao San

A classical Chinese formula prescribed for stress-related complaints. Meta-analyses report benefit in functional gut disorders and some mood outcomes, but nearly all trials are small, Chinese and at high risk of bias.

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What the science says

  • Benefit in functional gastrointestinal disorders Limited evidence

    A meta-analysis with trial sequential analysis of randomized trials found Xiao Yao San improved symptoms in functional gastrointestinal disorders compared with conventional treatment. The authors flagged low study quality and possible publication bias as limits on confidence.

  • Insomnia with anxiety Limited evidence

    A pooled analysis of randomized trials reported improvement in insomnia accompanied by anxiety, mostly compared against or added to standard drugs. Blinding was rare and follow-up short.

  • Blood pressure effects are uncertain Limited evidence

    A systematic review and meta-analysis in hypertension found reductions in blood pressure when the formula was added to antihypertensive drugs, but the evidence was rated low quality. It should not replace antihypertensive treatment.

Dosage & safety

Studied doseTrials typically used standard decoction or granule preparations two to three times daily for 4–8 weeks. Commercial granules generally follow the classical eight-herb ratio; follow the product label.
SafetyContains licorice, which in prolonged use can raise blood pressure and lower potassium. Herb quality and composition vary between manufacturers, and interactions with sedatives, anticoagulants and antihypertensives are plausible. Avoid in pregnancy and do not use in place of treatment for diagnosed depression or anxiety.

How to take it

TimingTaken two to three times daily, traditionally before meals.
With food?Take it with warm water before food; move it to after food if it upsets your stomach.
Worth knowingComposition varies a lot between manufacturers, so if a product seems to help, stay with that brand rather than switching.

Interactions

With medications

  • diuretics and corticosteroids

    The liquorice component causes potassium loss that these drugs compound. Avoid prolonged use together and have potassium checked

  • blood pressure medication

    Liquorice raises blood pressure and works against treatment. Limit to short courses and monitor blood pressure

  • antidepressants and sedatives

    Interactions are plausible but uncharacterised, and adding an unstudied herbal formula muddies whether the prescription is working. Tell your prescriber before starting and do not stop prescribed treatment

With other supplements

  • other liquorice-containing herbal formulas

    Liquorice effects on potassium and blood pressure add up across products. Do not run two liquorice-containing formulas at once

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

What is xiao yao san used for?

Xiao Yao San is a classical Chinese formula prescribed for stress-related complaints, with trials in functional gut disorders, insomnia with anxiety and hypertension. The evidence grade is limited because nearly all trials are small, Chinese and at high risk of bias.

Does xiao yao san help IBS or functional gut problems?

A meta-analysis found Xiao Yao San improved symptoms of functional gastrointestinal disorders compared with conventional treatment, but the authors flagged low study quality and possible publication bias. The evidence is limited.

Does xiao yao san help with anxiety and insomnia?

Pooled trials reported improvement with Xiao Yao San in insomnia accompanied by anxiety, mostly alongside or against standard drugs, with rare blinding and short follow-up (limited evidence). Do not use it in place of treatment for diagnosed depression or anxiety, and tell your prescriber before combining it with antidepressants or sedatives.

Is xiao yao san safe with blood pressure medication?

Xiao Yao San contains licorice, which in prolonged use can raise blood pressure and lower potassium, working against antihypertensives and compounding diuretics or corticosteroids. Limit it to short courses, monitor blood pressure, and avoid it in pregnancy.

Scientific references

Related in Stress & mood

Herbal medicines: what the evidence says (335)