Cannabis

What it feels like

The high, stage by stage — smoked and eaten — and what makes it tip one way or the other.

No two highs are quite the same. Across 30 studies, relaxation was what people reported most, but the effects varied widely between people and between occasions — sometimes in opposite directions.

Smoked or vaped

• Seconds to minutes, Arriving: THC reaches the brain almost at once, and the heart speeds up.
• 15–30 minutes, The peak: Relaxed and loose; things feel more intense and time starts to stretch.
• 1–3 hours, Settling: The high fades gradually over two to three hours.

Eaten

• 30–90 minutes, Nothing — then it creeps in: Eaten THC is absorbed slowly, so it takes a while to arrive.
• 2–3 hours, The peak: Later than smoking, and different: the liver turns much of the THC into 11-OH-THC, another active form, at levels close to the THC itself.
• 4–12 hours, A long tail: It can be felt for most of a day.

What it can feel like

• Relaxed: The most commonly reported effect.
• Slow time: You think far more time has passed than really has.
• Hungry: Food smells and tastes better; appetite switches on.
• Lost words: Sentences slip away halfway; stories get told twice.
• Big ideas: Ideas feel brilliant — though in a test, high doses made creative thinking worse.
• Music: It feels deeper — though in a scanner, the brain's reward response to music actually dropped.

And the same drug can turn. In a lab study, a low dose made a stressful task feel easier, and a higher one made mood worse and the task more threatening. Too much brings anxiety, panic and a racing heart, and paranoia rises with the anxiety and with things starting to look and sound strange. Time crawling makes it feel endless — but it passes.

Regular users feel some of this less: tolerance is strongest for the effects on thinking, and only partial for the high itself. CBD, the other main compound in cannabis, softens THC's paranoia and its hit to memory.

What's happening in the brain

Every part of the high, traced to where it happens. The model lights each one as you read.

Where THC lands

Your brain runs on its own cannabinoids. THC hijacks their CB1 receptors, which are densest in the cerebellum, the basal ganglia and the hippocampus. That map is the high: timing, movement, reward and memory are where it shows.

Why it feels good

Inhaled THC releases dopamine in the ventral striatum, around the nucleus accumbens — the brain's reward hub.

Why time stretches

There's no single clock in the brain: seconds to minutes are timed by circuits in the basal ganglia and cerebellum. On THC, people overestimate how long has passed — as if the internal clock were running fast. When your clock ticks faster than the world, the world seems slow. In a brain-scan study, the people whose cerebellum went quieter on THC were the ones whose sense of time was thrown off. Frequent users' timing barely moved.

Why you lose the thread

The hippocampus saves what's happening now as memories you can get back later. THC disrupts that saving step and leaves older memories alone — so the last thirty seconds go, and your childhood doesn't.

The munchies

In mice that had already eaten, cannabinoids switched on the hypothalamic neurons that normally signal fullness, but made them release a chemical that drives eating instead, and in hungry mice they made the smell pathway more sensitive, so food smelled stronger. In people living in a lab, smoking cannabis raised daily calories by 40%, all of it from extra snacks, mostly sweet ones.

Tolerance

In daily smokers, CB1 receptors across the cortex were reduced, more so the longer they'd smoked — and back to normal after about four weeks off. Fewer receptors, less effect from the same amount.

Does it last?

Across 69 studies of young people, frequent use went with a small dip in thinking and memory, and in studies that waited more than three days after last use, the dip was gone. Decades of heavy use are different: in a group followed from birth to 45, long-term users lost about 5.5 IQ points from childhood and had more memory problems, while people who'd quit showed little or none of it. It was worst in those who started as teenagers, and for them quitting didn't fully undo it. These studies follow people rather than test them, so they show a link more than a cause: in twin studies, a twin who used didn't lose more IQ than the twin who didn't.

Why breathing is spared

The brainstem, which runs breathing, has very few CB1 receptors — which is why cannabis on its own doesn't stop someone breathing.

Questions people ask

The things people wonder about while they're high — answered.

Risks and staying safe

The risks, plainly — and what to do if it turns.

The real risks

• Dependence: About 1 in 5 people who use cannabis develop a use disorder; about 1 in 3 young people who use weekly or more become dependent.
• Psychosis: Daily use of high-strength cannabis is linked to nearly five times the odds of a psychotic disorder, most of all in people with a genetic vulnerability.
• Driving: Crash risk roughly doubles.
• Starting young: About 1 in 6 people who start as teenagers become addicted, against about 1 in 11 overall.
• Hyperemesis: Some regular users develop cycles of severe vomiting; stopping is what fixes it.
• Edibles and kids: Keep edibles locked away — they look like sweets, and children who eat them can get very sick.

Keeping it good

• With edibles, start small and wait at least two hours before taking more.
• Lower-THC or THC-plus-CBD products are less likely to tip into paranoia.
• Avoid daily use, and don't drive.
• Skip it if psychosis runs in your family.

If someone's too high

1. Stay with them, somewhere calm: Paranoia is driven by anxiety, so quiet and a familiar face help.
2. Nothing more: No more cannabis, and no alcohol on top.
3. Remind them it ends: It wears off — hours for a smoke, longer for an edible.
4. Get help if…: There's chest pain, collapse or trouble breathing, or a child has eaten some.

Check what you know

Five questions about what's going on in a high.

• You're telling a story, and halfway through you realise you have no idea where it was going. What's THC doing? Stopping the hippocampus from saving what just happened — while older memories stay intact. THC reliably disrupts encoding new memories and leaves consolidated ones alone.
• You're sure you've been sitting on the sofa for an hour. The clock says nine minutes. Why? THC speeds up the timing circuits, so more seems to have passed than has. Interval timing runs through basal ganglia and cerebellar circuits, and on THC people overestimate elapsed time, consistent with a clock running fast.
• A friend ate a gummy 45 minutes ago and says it isn't working. What's going on? Edibles are absorbed slowly — it can take up to 90 minutes to arrive, then peak at 2–3 hours. Eaten THC starts in 30–90 minutes and peaks at 2–3 hours. Taking more now is how people overdo it.
• The first time you smoked a little, you felt great. The next time you had a lot more, and spent an hour convinced everyone was watching you. Why the difference? Dose: a little THC can calm, more can bring anxiety — and paranoia rides on the anxiety. A low dose eased stress and a higher one made mood worse, and THC's paranoia is driven by anxiety and strange perceptions.
• Someone who smokes every day says weed barely does anything for them any more. What's changed in their brain? They have fewer CB1 receptors in the cortex — which recover after about four weeks off. Daily smokers had fewer cortical CB1 receptors, back to normal after about four weeks without cannabis.