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.

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 improvements in tamoxifen-induced side effects although improvements affected by Jia Wei XYS were statistically non-significant ⁽²⁾.

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

Depression

In a systematic review conducted in 2012, 26 randomized clinical trials involving 1,837 depressive patients were assessed. The interventions employed included XYS or its modified forms, XYS plus antidepressants such as selective serotonin re-uptake inhibitors (SSRIs), tricyclics and tetracyclics, with antidepressants as controls.  Primary outcomes included the Hamilton depression rating scale (HAMD) and self-rating depression scale (SDS) scores. Data showed that XYS and its modified forms combined with antidepressants were superior to antidepressants alone. The formulae also improved the HAMD scores without increasing the number of adverse events ⁽³⁾.

In another review (5 XYS studies, 1,260 participants), Butler et al., 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 (40 trials with 3,549 that included 11 XYS studies) showed that CHM led to better clinical outcomes 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 (4 XYS trials with 1,441 gastric, lung, esophageal, breast and liver cancer patients) yielded similar findings. Compared to conventional antidepressants, CHM users experienced fewer adverse events of 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⁾.

In the latest analysis, Yang et al., assessed 55 studies (that included 12 XYS trials) involving 5,572 participants. Of these, 30 trials compared CHM vs SSRIs (fluoxetine, paroxetine and sertraline) whereas 25 compared CHM + SSRIs vs SSRIs.  Although the studies were of poor quality, CHM (with or without SSRIs) was associated with statistically significant improvements in HAMD scores with fewer, less severe adverse events ⁽⁷⁾.

Anxiety

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

In an 8-week multi-center trial, Su et al., randomized 191 patients with mild to moderate depression and anxiety to receive Jia Wei XYS or sertraline. Primary outcomes included HAMD, Hamilton Anxiety Rating Scale (HAMA) and Clinical Global Impression Scale scores. Jia Wei XYS was comparable to sertraline in all outcomes at the 8-week assessment, with sustained benefits at the 12-week follow-up. This suggests that the anti-depressive and anti-anxiolytic effects of Jia Wei XYS are more durable than those of sertraline. Jia Wei XYS was also associated with lower adverse event rate at the 12-week follow-up ⁽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. Furthermore, in patients with psychological stress insomnia, Jia Wei XYS, used alone or in combination with the benzodiazepene estazolam, affected subjective improvements in sleep quality ⁽¹⁰⁾.

Although accumulating evidence suggests benefits of both XYS and Jia Wei XYS, majority of the above mentioned studies are limited by small sample sizes, risk of bias, variations in treatment duration and dosage, and medication compliance. Larger methodologically robust trials are needed to determine the therapeutic potential of these formulations.