Ashwagandha eases stress in 22 pooled trials; by how much is unclear
The broadest pooling found stress, anxiety and depression scores falling on ashwagandha, and more at higher doses. The size it reports is several times what earlier trials found.
What the study found
Pooled over 22 trials, the stress drop is several times any trial's
Direction and size are two different questions. The broadest pooling of ashwagandha trials found stress, anxiety and depression falling against placebo, more so at higher doses. The size it reports is several times what earlier trials found, a reason to trust the direction over the number.
The caveat · A size no single trial supports
A pooled stress effect of nearly six standard deviations would mean almost nobody on placebo scored as low as anyone on ashwagandha, while earlier trials of the herb measured effects of 0.63 to 0.74 standard deviations. The authors themselves note the trials differed widely, and pooling very different trials can produce a size no single trial supports. The dose-response finding is read off the same pooling.
What we don't know
How much ashwagandha eases stress is unsettled. The poolings agree that it helps, but the largest reports an effect several times what single trials measured, and nothing yet explains the gap.