Eleutherococcus senticosus, sometimes called "siberian ginsing" (though there is question as to whether or not these are the same substance) is an adaptogen. An adaptogen is a substance that helps the body adapt to stresses of various kinds, whether heat, cold, exertion, trauma, sleep deprivation, toxic exposure, radiation, infection, or psychological... They do this by "normalizing" the body's processes - sometimes they act by calming the activity of systems that are exaggerated in the body, and sometimes they strengthen systems that are sluggish.
A fairly substantial (96-participant) double-blind, placebo-controlled study failed to find Eleutherococcus senticosus("Siberian ginseng") helpful for people with CFS.28 Over the 2-month study period, both eleutherococcus and placebo reduced fatigue symptoms, but there was no statistically significant difference. (The researchers managed to find some benefit by resorting to statistically questionable after-the-fact procedures.)
