Catnip: why some cats lose their minds, and others shrug

A third of cats are genetically immune to catnip, and the other two-thirds are helpless against it. The difference is a single inherited switch.

Give a responding cat a pinch of dried catnip and watch the sequence: the deep sniff, the cheek-rubbing, the rolling, the frantic licking, and ten minutes of behaviour that looks like pure euphoria. Offer the same pinch to a non-responder and you get a polite sniff and a walk-off. Both reactions are normal, and neither says anything about your cat's quality of life.

What is going on is one of the neatest pieces of chemistry in cat behaviour, and one of the most useful tools you can keep in a jar, if you know what it can and cannot do.

The chemistry of the madness

Catnip, Nepeta cataria, is a mint relative whose leaves and stems produce an oil called nepetalactone. The plant makes it to repel insects; cats detect it through the vomeronasal organ, a scent analyser in the roof of the mouth, which is why responders often open their mouths slightly in that odd, lip-curled grimace called the flehmen response.

Nepetalactone binds to receptors that plug straight into the brain's emotional circuitry. The resulting behaviour, rolling, rubbing, zoning, darting, looks like intoxication but is better understood as a brief, self-limiting behavioural programme. It runs for five to fifteen minutes, then switches off. The cat then becomes temporarily immune for an hour or two, which is why a second pinch straight after does nothing.

Catnip does not make cats happy so much as it presses a button they were born with, once, briefly, and then the circuit locks for an hour.

The genetic lottery

The response is inherited as a simple dominant trait. Roughly 50 to 70 per cent of cats carry it; the rest never will, no matter the dose or the quality. Several things follow:

Age matters as much as genetics. Kittens show no response before three months and often not until six, so a kitten ignoring catnip tells you nothing. Seniors usually keep the response for life, though it may soften.

The finder: is yours a responder?

If you have never tested your cat, or got a shrug and wondered why, the finder below reads age and past reactions and tells you what to expect, plus the best jobs for catnip in your particular home.

For non-responders, the worthwhile experiment is silver vine, a climbing plant from east Asia whose actinidine triggers the same circuitry through a different compound. Studies find that the majority of catnip-immune cats respond to silver vine, and valerian root works for a smaller share again. Between the three, very few adult cats are truly immune to everything.

Putting it to work

Catnip earns its cupboard space as a tool, not a treat. The jobs it does well:

• Scratching training: rub a pinch into the post or pad you want used, weekly. It is the most reliable way to redirect scratching onto furniture you chose, a trick we lean on in choosing a scratching post.
• Carrier and vet prep: a light sprinkle in the carrier thirty minutes before a trip settles many cats. Test at home first; a minority get more wound up, not less.
• Exercise for the reluctant: a catnip session gets a sedentary or older cat moving, useful support alongside the ideal-weight tool.
• Toy resurrection: store cloth toys in a sealed bag with a pinch of catnip overnight, and yesterday's ignored mouse becomes tomorrow's obsession.

Dosing, safety and storage

A serving is a pinch, about half a teaspoon of dried leaf. More does not extend or deepen the effect; the circuit simply locks after fifteen minutes regardless. Offer it once or twice a week at most, because cats exposed daily habituate and the response dulls.

On safety, the evidence is reassuring: catnip is non-addictive, causes no hangover, and cats self-regulate. Eating a large quantity can cause mild vomiting or diarrhoea, which is a reason to serve pinches rather than piles, and to store the jar out of reach. There is one caution: because it can briefly lower inhibition, give multi-cat sessions some space, and skip it entirely for a cat whose play tips into genuine aggression.

Verdict by household

Responder, single cat: a weekly pinch on the scratcher and a refilled toy in rotation. The simplest enrichment money cannot quite buy; expect to spend 5 to 10 EUR every few months.

Non-responder adult: try silver vine before giving up. If that fails too, valerian root is the last stop, and then wand play does the same job without chemistry.

Kitten household: wait until six months before judging. Meanwhile, the scratcher-training trick works on older housemates only.

Multi-cat home: offer catnip in separate zones or separate sessions. The communal pile is where mild squabbles start.

When to call your vet

Catnip itself almost never warrants a call. The exceptions: vomiting or diarrhoea that persists past a few hours after a session, which suggests your cat ate rather than inhaled a large amount; a session that reliably triggers real aggression toward housemates, which is a behaviour conversation; and any reaction that looks like tremors, disorientation or distress rather than the usual rolling, which is not catnip's profile and deserves a look. And if the jar went over and a quarter of it vanished into the cat, ring for advice and expect an upset stomach rather than a crisis.