Catnip (Nepeta cataria) is a perennial herb in the mint family, native to Europe and Asia but now grown across North America. The plant itself is unremarkable — a weedy, grey-green shrub that smells faintly herbal to humans. But hidden in microscopic bulbs on its leaves and stems is a compound called nepetalactone, and to roughly 60–70% of domestic cats, it is profoundly intoxicating.

Nepetalactone is a bicyclic monoterpenoid — a small, volatile organic molecule that evaporates quickly at room temperature, which is why crushed or bruised catnip smells stronger than intact leaves. When a cat sniffs catnip, nepetalactone binds to receptors in the nasal tissue and triggers a cascade of activity in the olfactory bulb and hypothalamus — the brain regions governing mood, pleasure, and sexual behavior.

The behavioral response — rolling, rubbing, vocalizing, drooling, and apparent euphoria — closely mimics a female cat in heat, which led early researchers to classify nepetalactone as a pheromone mimic. More recent work suggests it's more accurately described as a superstimulus: it doesn't replicate any single natural compound, but instead triggers the same neural pathways at a much higher intensity than anything cats encounter in nature.

The response is entirely olfactory. Eating catnip produces a mild sedative effect — almost the opposite reaction — because nepetalactone is metabolized differently when ingested. The classic catnip "high" only happens through smell. It lasts around 5–15 minutes, after which a refractory period of 30 minutes or more sets in, during which the cat becomes temporarily immune to catnip's effects. The brain simply stops responding until nepetalactone clears the receptors.

Sensitivity to catnip is hereditary, controlled by an autosomal dominant gene. A cat needs only one copy of the relevant allele to respond — but roughly 30–40% of cats are born without it entirely and will show zero interest no matter how much catnip you wave in their face. Kittens under 6 months old typically don't respond either, as the sensitivity appears to develop with sexual maturity.

Big cats are not exempt. Lions, tigers, leopards, and jaguars all show catnip responses at similar rates to domestic cats. Interestingly, nepetalactone has also been found to repel insects — particularly mosquitoes and aphids — leading some researchers to speculate that the cat response evolved as a way for cats to spread the compound across their fur as a natural insect deterrent, not just for recreation.

Catnip isn't the only plant that affects cats this way. Silvervine (Actinidia polygama), common in East Asian mountainous regions, produces two active compounds — actinidine and dihydroactinidiolide — and triggers a response in a broader range of cats than catnip, including many that don't respond to nepetalactone. Studies suggest up to 80% of cats respond to silvervine, making it particularly useful for cats that catnip leaves cold.

Valerian root (Valeriana officinalis) contains actinidine as well, producing a similar but generally mellower effect — more sedative than euphoric. Honeysuckle (Lonicera tatarica) wood shavings affect some cats through a different mechanism entirely, likely through a compound called neomatatabiol. And cat thyme (Teucrium marum), despite the name, is a completely different plant from regular thyme — it's a member of the germander family and produces a strong rolling-and-rubbing response through compounds that aren't yet fully characterized.

The practical upshot: if your cat doesn't respond to catnip, they're not broken — they're just missing one gene. Try silvervine first. It works on most of the holdouts.