Smoking catnip cannot get humans high; at most, it can cause headaches and vomiting, notes Francie Diep for Popular Science. There is a theory that humans are unable to feel the effects of catnip because they lack the same nepetalactone receptors in the brain that make cats sensitive to the substance. Thorough medical research has not been conducted on this topic, therefore scientists are uncertain why humans are not affected.
Catnip is a flowering plant used to make certain types of medicine, according to WebMD. Humans consume catnip in various forms, including teas and tonics. Catnip is sometimes applied directly to the skin to treat arthritis, hemorrhoids and swelling. It is also used to treat anxiety; insomnia; migraines; colds and other upper respiratory infections; flu; swine flu; fever; hives; worms; and gastrointestinal upset, such as indigestion, colic, cramping and gas. The tonic is used for increasing urination and for starting menstrual periods in girls with delayed onset of menstruation.
WebMD says that more evidence is needed to support the accuracy of these claims. Children and women who are pregnant or breastfeeding should not take catnip in any form. Women with pelvic inflammatory disease should not take catnip because it may induce menstruation.