Rhodiola rosea has been studied extensively and has been categorized as an adaptogen because of its ability to increase resistance to a variety of chemical, biological and physical stressors.  It is a popular plant native to Asia and Europe, with a reputation for supporting the nervous system by inhibiting the depletion of important brain neurotransmitters such as serotonin, dopamine and norepinephrine during times of stress.  Studies in Russia suggest that Rhodiola has great benefit in conditions where there is a decline in work performance, poor appetite, sleep disturbances, irritability and fatigue.  Some studies have found that medical students given Rhodiola during exams report improved concentration and performance, as well as enhanced well-being, improved sleep and greater mood stability.  In addition to enhancing mood and better sleep, Rhodiola can also help decrease episodes of worry and nervousness supporting the body to function more efficiently under stressful situations.