How someone acts while high depends almost entirely on what substance they’ve used. Cannabis makes people slow and giggly, stimulants make them wired and restless, opioids make them drowsy and disconnected, and hallucinogens can make them emotionally unpredictable. But within each category, there are specific behavioral patterns that are surprisingly consistent from person to person.
Cannabis: Slow, Giggly, and Hungry
A person high on cannabis typically seems relaxed and a little out of it. The classic signs are red eyes, dry mouth, uncontrollable laughter (often at things that aren’t particularly funny), and a sudden intense interest in food. They may seem inattentive or forgetful mid-conversation, losing their train of thought or repeating themselves. Time feels distorted to them, usually slower, so they may seem unhurried or spacey.
Motor coordination drops noticeably. Movements become slightly clumsy, reaction times slow down, and judgment gets impaired. Some people become very talkative and social, while others withdraw and get quiet. At higher doses, cannabis can trigger anxiety or paranoia, and you might notice someone becoming visibly uncomfortable, restless, or suspicious of their surroundings for no clear reason. Their pupils tend to dilate, though the bloodshot eyes are usually the more obvious giveaway.
Stimulants: Wired, Fast, and Restless
Cocaine and methamphetamine produce a dramatically different picture. Someone on stimulants often talks rapidly, sometimes jumping between topics or interrupting others. They seem unusually alert, energetic, and confident. Their appetite disappears, they may not sleep for long stretches, and their sex drive can spike. Physically, you’ll notice dilated pupils, brisk or jerky movements, and a slightly quivering voice in some cases.
The behavior shifts as a high wears off or during extended use. Irritability, anxiety, and agitation become more prominent. Methamphetamine in particular is strongly linked to paranoia, with users sometimes developing suspicions that feel completely real to them. Auditory and tactile hallucinations (hearing things or feeling sensations like bugs under the skin) can develop during binges. Violent behavior sometimes accompanies these paranoid states. Someone deep in a stimulant binge, sometimes called “tweaking,” may appear outwardly normal at first glance, with clear eyes and coherent speech, but closer observation reveals restless gestures and an inability to stay still.
Opioids: Drowsy, Slow, and Detached
Opioids like heroin, fentanyl, and prescription painkillers produce a sedated, dreamy state. The person feels euphoric but looks sleepy. The hallmark physical sign is pinpoint pupils, tiny even in dim lighting, which is the opposite of what most other drugs cause. Speech becomes slow and slurred. They may “nod off” repeatedly, drifting in and out of consciousness mid-sentence or while sitting upright.
Their movements are sluggish and their emotional responses feel muted or delayed. They often seem content but disconnected from their surroundings. The line between a high and an overdose can be dangerously thin with opioids. If someone becomes impossible to wake, their breathing drops below about 8 breaths per minute, their skin turns bluish or clammy, or they stop responding entirely, that’s no longer just being high. That’s a medical emergency.
Hallucinogens: Emotional, Distracted, Unpredictable
LSD, psilocybin mushrooms, and similar substances create a state that’s hard to predict from the outside. Someone tripping may stare at ordinary objects for long periods, seemingly fascinated. They might describe colors they can “hear” or sounds they can “see,” a phenomenon called synesthesia where the senses blend together. Emotions swing rapidly and intensely: profound joy, deep sadness, awe, or fear can cycle within minutes.
Their pupils are usually very dilated. They may seem deeply introspective or spiritually preoccupied, talking about meaning or connection in ways that feel intense and unusual for them. During a difficult experience (a “bad trip”), paranoia, panic, and a disturbing sense of losing their identity can take over. They might become aggressive or deeply withdrawn. Time distortion is extreme, and minutes can feel like hours to them, which makes reassurance tricky.
Alcohol: Loud, Uncoordinated, and Disinhibited
Alcohol is the most familiar intoxicant, but its effects on behavior are worth spelling out because they follow a predictable progression. At lower levels, people become more talkative, socially confident, and emotionally expressive. Inhibitions drop, leading to louder speech, more physical contact, and riskier decisions. Pupils dilate slightly.
As blood alcohol rises above roughly 0.05 g/dL, motor coordination deteriorates measurably. Fine motor skills suffer first: fumbling with phones, knocking over glasses, struggling with keys. Balance and gait become unsteady. Reaction time slows. Studies using dexterity tests show that even heavy drinkers experience the same degree of motor impairment as light drinkers at equivalent doses, about four to five standard drinks. The feeling of being “fine” doesn’t match reality. At dangerous levels, alcohol overdose symptoms include mental confusion, vomiting, seizures, irregular breathing (10 seconds or more between breaths), clammy skin, and inability to stay conscious.
How Intoxication Changes Social Behavior
Across substances, being high tends to impair the ability to read other people accurately. Research on people with substance use problems found that over 70% showed measurable difficulty recognizing emotions like fear, sadness, anger, and disgust in others’ faces. Interestingly, the ability to understand hints or infer what someone means in conversation stayed relatively intact. So a person who is high might follow the words you’re saying but completely miss your emotional tone or body language.
There’s also a consistent shift toward interpreting neutral social situations as hostile. People under the influence, especially of stimulants, score higher on measures of hostility bias, meaning they’re more likely to assume someone is being aggressive or intentionally disrespectful when that’s not the case. This helps explain why minor misunderstandings can escalate quickly when drugs or alcohol are involved.
Physical Signs at a Glance
The eyes are one of the most reliable indicators of what someone has taken. Stimulants, hallucinogens, and cannabis all cause dilated pupils. Opioids do the opposite, constricting pupils to tiny pinpoints. Alcohol causes mild dilation. One exception worth noting: PCP (angel dust) doesn’t change pupil size but often causes a distinctive rapid eye movement called nystagmus, where the eyes bounce horizontally or vertically.
Beyond the eyes, body temperature and movement patterns tell a story. Stimulant users run hot and can’t sit still. Opioid users run cool and barely move. Cannabis users move slowly but normally. Hallucinogen users may alternate between frozen stillness and sudden bursts of activity. These physical patterns, combined with behavioral changes, make it possible to get a reasonable sense of what substance is involved even without being told.