Uncertainty exists regarding the ability of catnip (Nepeta cataria) to affect human consciousness. We report a case of a toddler exhibiting central nervous system depression after consuming a large quantity of catnip. His obtundation was not attributable to another cause. We review the published literature describing the alleged psychoactive capabilities of catnip and present our case as further information for use in this ongoing controversy.
– Vet Hum Toxicol 1997 Dec;39(6):373-5 — Catnip and the alteration of human consciousness. — Osterhoudt KC, Lee SK, Callahan JM, Henretig FM.

Acute exposure to catnip increased stereotyped behavior and susceptibility to seizures, did not interfere with haloperidol-induced catalepsy, and decreased sleeping time after sodium pentobarbital administration. Long-term exposure induced tolerance to stereotypic behavior, catalepsy and sleeping time, and increased the susceptibility to seizures induced by picrotoxin and strychnine. An amphetamine-like effect of catnip was suggested to explain the acute effects, while dispositional and functional adaptative changes were considered involved with the long-term effects.
– Vet Hum Toxicol 1995 Dec;37(6):530-3 — Behavioral effects of acute and long-term administration of catnip (Nepeta cataria) in mice. — Massoco CO, Silva MR, Gorniak SL, Spinosa MS, Bernardi MM.

Not recommended if you are pregnant or nursing.