http://www.sciencedirect.com/science/article/pii/S0944711300800550

Rhodiola rosea in stress induced fatigue — A double blind cross-over study of a standardized extract SHR-5 with a repeated low-dose regimen on the mental performance of healthy physicians during night duty

• V. Darbinyan^1, *, ,
• A. Kteyan¹,
• A. Panossian²,
• E. Gabrielian²,
• G. Wikman³,
• H. Wagner⁴

Study Summarise:
56 healthy young men who worked night shifts as physicians, consumed a low dose of Rhodiola rosea.
Fatigue Index was used to calculate the effects of the herb. The Index reflected overall level of mental fatigue, involving complex perceptive and cognitive cerebral functions, such as associative thinking, short-term memory, calculation and ability of concentration, and speed of audio-visual perception.
The scientists measured fatigue index during a period two weeks, before and after night duty.
The first two weeks the subjects consumed either Rhodiola Rosea or a placebo.
The second two weeks nothing was consumed (other than there normal diets etc.)
The third week the subjects consumed either Rhodiola Rosea or a placebo again.

A statistically significant improvement in the Fatigue Index tests was observed in the treatment group (Those consuming Rhodiola Rosea) during the first two weeks period. No side-effects were reported for either treatment noted.