Updated clinical evidence of Chinese herbal medicine for insomnia: A systematic review and meta-analysis of randomized controlled trials

Abstract

This systematic review is to evaluate the efficacy and safety of Chinese herbal medicine (CHM) for people with insomnia. Randomized controlled trials (RCTs) investigating oral CHM alone or in combination with conventional therapies for primary insomnia were identified by searching English and Chinese publications and databases of clinical trial registration. Risk of bias was assessed according to the Cochrane Handbook 5.1. Meta-analysis was conducted using RevMan 5.2.4. Seventy-nine trials (7886 participants) were finally included in the review, and 76 were included in the meta-analysis. Twenty-seven trials reported the methods of random sequence generation, and five of them used the allocation concealment. Blinding of participants and personnel were used in 10 studies. The main meta-analysis showed that CHM alone was more effective than placebo by reducing scores of Pittsburgh Sleep Quality Index (mean difference, MD: -3.06, 95% confidence interval, CI: -5.14 to -0.98, I2 = 97%) and benzodiazepine drugs (BZDs) (MD: -1.94, 95% CI: -2.45 to -1.43, I2 = 96%). The effect was also seen when CHM was combined with BZDs compared with placebo plus BZDs (MD: -1.88, 95% CI: -2.78 to -0.97, I2 = 0%) or cognitive and behavioral therapy (MD: -3.80, 95% CI: -4.91 to -2.68, I2 = 68%) alone. There was no significant difference between CHM and placebo regarding the frequency of adverse events (relative risk, RR: 1.65, 95% CI: 0.67-4.10, I2 = 0). Overall, oral CHM used as a monotherapy or as an adjunct to conventional therapies appears safe, and it may improve subjective sleep in people with insomnia. However, the typical effect of CHM for insomnia cannot be determined due to heterogeneity. Further study focusing on individual CHM formula for insomnia is needed. The development of a comparable placebo is also needed to improve the successful blinding in RCTs.