The Legend: Catnip contains psychoactive oils and smoking it can get you high.
Catnip, Nepeta cataria L., is a very interesting plant. It is a flowering herb that grows in North America and is probably most well known for its effects on cats. Catnip's power comes from nepetalactone, a volatile oil.
Nepetalactone has been used medicinally for thousands of years as an antispasmodic, a sedative and a treatment for diarrhea, colic, the common cold, leprosy and even cancer. It can be brewed into a tea, powdered, or cooked into soups and stews. Some references on this plant say that smoking catnip can produce euphoria and visual hallucinations, others say just the opposite.
Perhaps the most talked about reference to smoking catnip was a 1969 article in the Journal of the American Medical Association that suggested that smoking catnip would get you high, (Jackson, 1969). A few hundred readers responded to this article, pointing out that the accompanying photograph was actually a marijuana plant. It seems the author had confused catnip with marijuana. Ooops.
It is now generally accepted that catnip has no hallucinogenic properties when smoked. Message boards are full of accounts of disappointed catnip smokers.
As for the other medicinal benefits, there is no harm in brewing yourself a cup of catnip tea and seeing if it settles your stomach.
Interesting factoid: Nepetalactone has shown itself to be an incredibly effective, non-toxic insect repellent, (Amer & Mehlhorn, 2006).