Somewhere in Siberia around 23,000 years ago, a particularly brave wolf or wolves wandered into a human campsite in search of food and the humans and said animal were apparently like “Did we just become best friends?!?!?!?” 23 millennia of selective breeding later, and we have succeeded in turning a once wild and fearsome beast into chihuahuas… And also such a good boy! Yes you are, yes you are!

…and then there’s cats, who probably took one look at what happened to dogs like the chihuahua, said “f***k that noise”, and decided to domesticate us instead. Now, we do absolutely everything for our feline friends – keep them in a nice warm house, feed them delicious wet food, and scoop their litter box – while expecting very little in return aside from the occasional round of pest control or a grudgingly-given cuddle so long as we hold completely still and don’t move a freaking muscle. We even buy them recreational drugs. Known as “the nip” on the streets, this illicit substance is so ubiquitous used by our feline friends that its full street name also includes theirs- catnip– that magical herb that sends sweet Mittens rolling, flipping, and occasionally drooling on the floor in a haze of pure bliss. But what even is catnip anyway, and does it actually get cats high? Well, grab your favourite furry middle manager as we dive into the fascinating science of catnip.

Napeta cataria, also known as catmint, catwort, and of course catnip, is a small perennial shrub with elliptical saw-edged leaves and white-purple orchid-shaped flowers. Originally native to large areas of Europe, Asia, and Africa, catnip was introduced to North America by European settlers and is now widespread across the continent, often found growing in roadside ditches. Catnip belongs to the family Lamiaceae, which also includes most of the common culinary herbs like basil, peppermint, rosemary, sage, and oregano. Like those herbs, catnip produces aromatic essential oils, which are stored on the surface of the leaves, stems, and seedpods in microscopic bulbs called trichomes, which naturally burst and release the oil when they mature. However, they can also be ruptured by insects feeding or larger animals – like cats – rubbing up against the plant.

Catnip oil contains a variety of aromatic compounds including nepetalactone, which is believed to be what makes our furry friends trip out like they’re rocking out at feline Woodstock. Unfortunately, much of what we currently know about the effect of catnip on cats’ brains is heavily based on theory; after all, getting a bunch of cats hopped up on the nip to sit still in an MRI is not exactly a practical proposition. Nonetheless, there are many compelling clues as to what might be going on inside Felix’s little noggin. For one thing, the most common behaviours induced by catnip – sniffing, licking, chewing, body and head rubbing, shaking, loudly vocalizing – and flipping or rolling around on the floor – are very similar to those exhibited by female cats in heat. Furthermore kittens don’t become susceptible to catnip until approximately six months of age – around the time they start reaching sexual maturity. This suggests that nepetalactone mimics the action of one or more feline sex pheromones. Originally, scientists believed that nepetalactone directly stimulated the vomeronasal or Jacobson’s organ – an olfactory or smell organ found in many animals but not humans which is involved in the detection of sex pheromones. However, a 1985 study published in the Journal of Behavioural and Neural Biology determined that removing the vomeronasal organ has no effect on cats’ sensitivity and reaction to catnip. Nepetalactone, the study concluded, must thus be detected by the regular olfactory receptors, stimulating various regions of the brain including the olfactory bulb, amygdala, hypothalamus, and pituitary gland to produce a sexual – and euphoric – response. In most cats, this response lasts for about ten minutes before suddenly ceasing, whereupon the cat enters a state of passive relaxation or stupor. At this point it can take up to 30 minutes for the cat’s system to reset and become re-sensitized to the catnip.

But while cats on catnip might look like they’re seconds away from driving to White Castle with a major case of the munchies, there was originally no evidence that catnip effects feline brains like marijuana, opium, cocaine and other drugs affect human brains – that is, by triggering the release of dopamine or stimulating natural opioid receptors. Indeed, cats appear to be fully aware while supposedly “tripping” on catnip, and if disturbed will resume their normal behaviours with no impairment of cognition or motor function. Furthermore, the reaction is exactly the same every time, with no evidence that cats can overdose on – or develop a tolerance to – catnip, though ingesting too much can irritate the digestive tract, leading to dizziness, vomiting and diarrhea. And the editor of this piece once had a cat get into a bulk giant bag of catnip and tear it open, only to be discovered later that day laying on his back covered in catnip with drool all over his face and otherwise relatively catatonic (the cat, not the editor) on his makeshift catnip bed for a little while after, only fully back to normal a few hours later. In any event, on this note, a 2021 study led by Professor Masao Miyazaki of Iwate University in Japan revealed that naloxone – an antagonist drug used to reverse the effects of opiate overdose – can completely eliminate cats’ reaction to catnip. Miyazaki and his colleagues also measured elevated levels of beta-endorphins – the body’s natural painkilling chemicals – in the cats’ bloodstream immediately following exposure to catnip, suggesting that the opioid system may in fact play some role in the herb’s physiological effects.

While inhaled catnip usually produces an energetic response, when ingested the herb has the opposite effect, making cats relaxed and mellow. This is unsurprising, since the herb has been used by humans for centuries as a mild sedative, with catnip infusion having similar calming properties to chamomile tea. It was also traditionally used to treat all manner of ailments including infant colic, migraines, cramps, gas, indigestion, and arthritis. Indeed, the medicinal properties of catnip are the reason it was imported to North America in the first place. In the 1960s, catnip was even touted as a cheaper and legal alternative to marijuana. However, its purported psychoactive properties were almost certainly a case of wishful thinking, for later scientific studies revealed that it has no such effects on the human brain.

Interestingly, not all cats appear susceptible to catnip, with sensitivity being strongly hereditary; that is, a kitten with one catnip-sensitive parent will have a 50% chance of being sensitive, while one with two sensitive parents will have a 75% chance. Breed, colour, and sex appears to have no effect on catnip sensitivity, while many wild cats including jaguar, lynx, leopards and cheetahs are just as sensitive to the herb as their domestic cousins; indeed, North American hunters traditionally used catnip to lure mountain lions. Strangely, however, tigers appear to be immune… perhaps they simply prefer frosted flakes. Originally, it was thought that around 70-80% of cats were sensitive to catnip, but a recent study by Dr. Bruce Kornreich of the Cornell University College of Veterinary Medicine suggests that many cats previously thought to be insensitive to catnip in fact simply exhibit a less active response:

“They assume what’s called a kind of sphinx position, and they vocalize less. The results of this study suggest that a much higher percentage of cats — if not all cats — are somehow affected by catnip.”

But whatever the actual percentage, the fact that not all cats respond to catnip suggests that the genes for catnip sensitivity were acquired relatively recently in feline evolution. And the rapid spread of these genes further suggests that catnip sensitivity confers some manner of evolutionary advantage. But what possible advantage can cats possibly get from a plant that induces euphoria?

One answer suggested by Professor Masao Miyazaki – who also discovered the effects of catnip on cats’ opioid receptor systems – is that catnip exposure protects cats from insect bites. In the 1960s, Cornell University naturalist Thomas Eisner discovered that catnip oil was 10 times more effective than N,N-diethyl-meta-toluamide – AKA DEET – the synthetic active ingredient in most insect repellents. Indeed, catnip-based sprays are still available today as a natural alternative to DEET-based repellents, though they break down more quickly than DEET and must be reapplied more regularly. But we’re also assuming have the side effect of making it so your cats pretend to like you for a little bit outside of feeding time.

To test the natural repellent properties of catnip and silver vine – an unrelated plant native to China and Japan that produces similar compounds – Miyazaki and his colleagues placed the heads of sedated cats into chambers full of mosquitos and counted how many insects landed on them. Some of the cats were treated with catnip and silver vine extract, while others were treated with a neutral substance. The experiment, published in the January 2021 issue of the journal Science Advances, revealed that only around half the number of mosquitoes landed on the treated versus the non-treated heads. The evolutionary advantage, Miyazaki argues, is obvious:

“Anyone who has ever sat in the field to observe animals ambushing prey knows just how difficult it is for them to keep still when there are many biting mosquitoes around. “It does not seem unreasonable, therefore, to argue that there is a strong selection pressure [to keep these insects at bay].”

Whatever the case there, the psychoactive effects of catnip are thus likely a happy side-effect – one that helped reinforce the even more beneficial insect-repellent properties of the plant.

Today, of course, the pampered indoor lives of our feline friends makes the practical advantages of catnip irrelevant, turning the herb into a purely recreational substance we gladly supply our feline masters.

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