An investigation into the acute nootropic effects of Hypericum perforatum L. (St. John's Wort) in healthy human volunteers

Hypericum perforatum L, (St, John's Wort) is a complex herb that has been u sed for centuries for its putative medicinal properties, and has current th erapeutic relevance as a treatment of mild to moderate depression. Recently , two studies in rodents have suggested that hypericum may also have memory -enhancing effects. It has a complex pharmacology, in that acute administra tion modulates numerous neurotransmitter systems that have previously been observed to either augment or impair a variety of memory processes in human s. This study aimed to examine whether acute administration of standardized hypericum extract could exert a nootropic effect in normal human subjects. The study employed a double-blind, crossover, repeated-measures design. Tw elve healthy young subjects completed the Cognitive Drug Research (CDR) mem ory battery, following administration of placebo, 900 mg and 1800 mg hyperi cum (Blackmore's Hyperiforte), The findings suggested that hypericum does n ot have an acute nootropic effect in healthy humans at these doses. However , there was some evidence for an impairing effect on accuracy of numeric wo rking memory and delayed picture recognition at the higher dose. This obser ved impairment could be due to a sensitivity of these specific tasks to mod ulation by neurotransmitters that have been noted to have memory-impairing effects (e.g. gamma -aminobutyric acid (GABA), serotonin), (C) 2001 Lippinc ott Williams & Wilkins.