Xiao Yao San (XYS) is a traditional Chinese medicine (TCM) formula documented in Tai Ping Hui Min He Ji Ju Fang, a collection of prescriptions written during the Song Dynasty around 1078-1085 AD. It consists of eight herbs: Bupleuri radix (Chai Hu), Angelicae radix (Dang Gui or Dong Quai), Paeoniae radix alba (Bai Shao), Atractylodis rhizome macrocephalae (Bai Zhu), Poria cocos (Fu Ling), Zingiberis siccatum rhizome (Sheng Jiang), Menthae haplocalycis (Bo He), and Glycyrrhizae radix (Gan Cao or Licorice). Xiao Yao San has a long history of use as a treatment for depression, anxiety and stress. Accumulating evidence also suggests its potential as a treatment for functional gastrointestinal disorders ⁽²⁴⁾.

A modified version known as Dan Zhi XYS or Jia Wei XYS was developed with two additional herbs with cooling properties: Cortex Moutan (Mu Dan Pi) and Fructus Gardeniae (Zhi Zi). This formulation is used both in China and Japan to manage symptoms such as mood, anxiety, fatigue, and insomnia associated with climacteric syndrome. Jia Wei XYS is also the most prescribed product for breast cancer patients according to the Taiwan health insurance research database ⁽¹⁾. In addition, a large retrospective study found that Jia Wei XYS was frequently utilized (nearly a third of all herbal prescriptions) by breast cancer patients treated with tamoxifen. The authors reported notable reductions in the risk of endometrial cancer along with statistically non-significant improvements in tamoxifen-induced side effects ⁽²⁾. Another study of cervical cancer patients in Taiwan reported reduction in mortality rate and improvement in survival probability with adjunctive use of Jia Wei XYS ⁽²⁵⁾. This formula has also been positively correlated with reduced risk of dementia ⁽²⁶⁾.

Below are the major symptoms for which XYS and Jia Wei XYS are prescribed along with current clinical evidence.

Depression

A systematic review of 26 RCTs involving 1,837 depressive patients found that XYS and its modified forms combined with antidepressants (selective serotonin re-uptake inhibitors (SSRIs), tricyclics and tetracyclics) were superior to antidepressants alone. The formulae also improved HAMD scores without increasing the number of adverse events ⁽³⁾.

Another review of 5 XYS studies with 1,260 participants concluded that despite some positive findings, the use of Chinese herbal medicine (CHM) for depression cannot be fully substantiated ⁽⁴⁾. But growing evidence since then suggests otherwise. A meta-analysis of 40 trials, which included 11 XYS studies, with 3,549 participants reported better clinical outcomes with CHM based on HAMD scores. Furthermore, adding CHM to conventional treatments reduced the adverse effects associated with their use; CHM alone also caused fewer adverse events compared with antidepressants ⁽⁵⁾. An additional review of 55 studies, which included 12 XYS trials, with 5,572 participants yielded similar findings: CHM with or without SSRIs (fluoxetine, paroxetine and sertraline) was associated with statistically significant improvements in HAMD scores causing fewer, less severe adverse effects ⁽⁷⁾.

XYS may also be relevant in cancer settings. In a review of 18 trials, which included 4 XYS studies, and 1,441 gastric, lung, esophageal, breast and liver cancer patients, CHM users had fewer side effects compared to conventional antidepressants. Adverse events included functional gastrointestinal disorders, sleep disturbances, blurred vision, and fatigue. However, the authors did not perform subgroup analysis for the different cancer types or disease stage ⁽⁶⁾.

Anxiety

Both XYS and Jia Wei XYS have been studied for their potential anxiolytic effects. A systematic review and meta-analysis of 9 trials with 681 patients reported that XYS, alone or in combination with conventional medicine, helped improve sleep quality and relieve anxiety ⁽²³⁾.

In an 8-week, multi-center trial of 192 patients with mild to moderate depression and anxiety, Jia Wei XYS was comparable to sertraline in improving HAMD, HAMA, and Clinical Global Impression Scale scores with sustained benefits at the 12-week follow-up. Jia Wei XYS was also associated with lower adverse event rate ⁽⁸⁾.

Insomnia

Data show that 40-60% of patients with mood disorders develop insomnia before developing symptoms associated with mood disorders ⁽⁹⁾. In the trial described above ⁽⁸⁾, the authors reported that in addition to improving anxiety, Jia Wei XYS also affected reductions in symptoms of sleep disorder at the 12-week follow up. Additionally, in patients with psychological stress insomnia, Jia Wei XYS, used alone or in combination with the benzodiazepene estazolam, led to subjective improvements in sleep quality ⁽¹⁰⁾.

Although current evidence suggests benefits of both XYS and Jia Wei XYS, majority of the above mentioned studies are limited by small sample size, risk of bias, variations in treatment duration and dosage, and medication compliance. Larger, methodologically-robust trials are needed to generate more definitive data.