The exact way that horny goat weed works remains unclear. Animal studies have shown that it may influence levels of neurotransmitters such as norepinephrine, serotonin, and dopamine and reduce cortisol levels.
It is interesting to note that although at least 15 fifteen active compounds have been identified in epimedium extracts, (luteolin, icariin, quercetin, and various epimedins), many supplement companies currently use alcohol extracts standardized only for high levels of icariin.
Because all of the existing scientific evidence for the anti-stress and cortisol-controlling effect of epimedium has been demonstrated for water-extracted epimedium (that is, as a tea), and because this form of extraction may result in a safer form of epimedium (compared to the high-icariin alcohol extract), it may be prudent to select supplements that specifically use a more traditional formulation.
There have been no reports of adverse side effects associated with the traditional preparation of epimedium (water-extracted) at the suggested dosage (250-1,000mg/day in 2-3 divided doses).