When you’re high on cannabis, THC triggers a cascade of changes across your brain and body. Your heart rate climbs, your eyes redden, time feels distorted, and your mood shifts anywhere from deep relaxation to intense anxiety. These effects can start within seconds of inhaling or take up to two hours with edibles, and the experience varies widely depending on how much you consume and how you consume it.
How THC Changes Your Brain
THC works by binding to receptors spread throughout your brain, including areas responsible for memory, learning, motor skills, and emotional responses. Once locked in, THC increases dopamine activity in your brain’s reward circuits, which is what produces the euphoria and heightened pleasure most people associate with being high.
This receptor system also influences the parts of your brain that process fear and anxiety. At low doses, THC tends to activate pathways that calm you down. At higher doses, it flips, activating different circuits that can trigger anxiety and paranoia instead. This biphasic effect is one reason the same substance can make one person giggly and relaxed while leaving another person panicked on the couch.
What You Actually Feel
The classic high includes euphoria, relaxation, heightened sensory experiences, and a general sense that everything is more interesting or funny than usual. Music can sound richer, food tastes more intense, and colors may seem more vivid. These sensory changes are tied to THC’s influence on higher brain function and the way it alters how your brain processes incoming information.
Time distortion is one of the most consistent effects. Minutes can feel like hours. Researchers believe this happens because THC disrupts two separate timing systems in the brain: one that tracks very short intervals (under a second, managed by deeper brain structures) and another that handles longer stretches of time (governed by circuits connecting the outer brain to deeper relay centers). The result is that your internal clock genuinely runs differently while you’re high.
Not everyone gets the pleasant version. Higher doses are linked to increased reports of panic, paranoia, and anxiety. If you’ve ever felt like your heart was beating too fast or that something was deeply wrong while high, that’s the dose-dependent flip at work.
Physical Effects on Your Body
Red eyes are probably the most visible sign someone is high, and they have nothing to do with smoke irritation. THC causes blood vessels throughout your body to widen, increasing blood flow and lowering blood pressure. The tiny blood vessels in your eyes dilate too, flooding them with blood and creating that telltale redness. This same blood vessel widening is why some people feel lightheaded or dizzy when they stand up quickly while high.
Dry mouth is another near-universal effect. Your heart rate also increases, sometimes noticeably. Some people experience sudden sweating, hot flashes, or cold chills, particularly at higher doses.
Why You Get So Hungry
The “munchies” are real and measurable. In a 2025 study published in PNAS, vaporized cannabis acutely and significantly increased the amount of food people ate, with the effect kicking in within the first 30 minutes of having food available, regardless of dose or gender. In animal models, cannabis reduced the delay before eating began and increased the number of feeding episodes.
Interestingly, the study found that cannabis did not change levels of ghrelin (the hunger hormone) or any other appetite-related hormones in the blood. The hunger signal isn’t coming from your gut. Instead, it originates from receptors in the brain itself, including in areas that process smell. THC appears to dampen certain signals in your brain’s smell-processing region, which may make food aromas more rewarding and harder to resist. The hunger feels intense because your brain is telling you food is more valuable than it normally is, increasing both your motivation to eat and the reward you get from eating.
Motor Skills and Coordination
THC measurably impairs your ability to move quickly and maintain balance. In a controlled study, arm speed dropped by about 15% immediately after using cannabis concentrates and stayed impaired an hour later, declining 16% from baseline. Leg speed decreased by 7% within an hour. Balance worsened immediately after use, with increased postural sway whether participants’ eyes were open or closed, though this particular effect faded within the hour.
Fine motor control tells a more nuanced story. Finger tapping speed wasn’t affected at all in the same study, suggesting that THC primarily impacts larger, whole-body movements rather than small, repetitive ones. One surprising finding: the amount of THC in participants’ blood didn’t correlate well with how impaired they actually were. Two people with similar blood levels could have very different levels of motor impairment, which is part of why measuring cannabis intoxication is so much harder than measuring alcohol intoxication.
How Long It Lasts
The timeline depends entirely on how you consume cannabis. When you smoke or vape, effects begin within seconds to a few minutes. They peak within about 30 minutes and can last up to 6 hours, with some residual effects lingering up to 24 hours.
Edibles follow a completely different curve. You won’t feel anything for 30 minutes to 2 hours after eating. Effects peak around 4 hours in, and the whole experience can stretch to 12 hours, with residual effects also lasting up to 24 hours. This slow onset is the main reason people accidentally overconsume edibles. They eat a dose, feel nothing after an hour, take more, and then both doses hit at once.
When It Goes Wrong: Greening Out
Consuming too much THC leads to what’s commonly called “greening out.” This isn’t dangerous in the way an alcohol overdose can be, but it feels terrible. Symptoms include nausea and vomiting, rapid or pounding heartbeat, excessive sweating, intense anxiety or paranoia, abdominal pain, and a feeling of being physically locked in place, unable to move.
If this happens to you, the approach is simple: hydrate, lie down somewhere safe, and focus on slow, deep breathing. The experience is self-limiting and will pass as THC is metabolized. No medical intervention is typically needed unless symptoms are severe enough to cause genuine distress, in which case the focus is on hydration, comfort, and calming the anxiety until it subsides.
Greening out is more common with edibles because of that delayed onset. It’s also more likely if you mix cannabis with alcohol, if you haven’t eaten, or if you’re using a product with a THC concentration higher than what you’re used to.