Speed, the street name for amphetamine, produces an intense rush of energy, confidence, and euphoria that typically lasts three to six hours. The drug floods the brain with feel-good chemicals, creating a high that affects nearly every system in your body, from your mood and focus to your heart rate and appetite. What follows that high, though, is often the opposite: deep fatigue, irritability, and low mood that can persist for days.
The Initial Rush
When speed hits, the first thing most people notice is a surge of euphoria and alertness. The world feels sharper. Thoughts come faster. There’s a sense of confidence and social openness that can feel almost invincible. Many users describe feeling hyper-focused, extremely talkative, and physically energized, as though they could take on anything. The mood shift resembles a hypomanic state: elevated, goal-driven, and impulsive.
How quickly this kicks in depends on how it’s taken. Snorting produces effects within a few minutes. Swallowing it takes anywhere from 20 minutes to an hour. Either way, the peak high lasts roughly three to six hours, though residual stimulation can linger much longer.
What Happens in the Brain
Speed works by forcing nerve cells to release large amounts of stored chemical messengers, primarily dopamine and norepinephrine. Normally, these chemicals are released in small, controlled bursts and then recycled back into the cell. Amphetamine disrupts that recycling process and simultaneously pushes stored reserves out into the gap between neurons, where they amplify signals related to pleasure, motivation, alertness, and physical arousal.
The dopamine flood is what drives the euphoria and the feeling that everything is rewarding and interesting. The norepinephrine surge is responsible for the physical side: the racing heart, the jittery energy, the sense that your body is running at full throttle. It also suppresses hunger by interfering with appetite-regulating signals in the brain’s feeding centers, reducing both the chemical triggers for hunger and the motivation to eat.
Physical Sensations
Speed doesn’t just change your mood. It puts your body into a pronounced fight-or-flight state. Common physical effects include:
- Rapid heartbeat, often exceeding 100 beats per minute, sometimes with palpitations or a pounding sensation in the chest
- Dilated pupils and heightened sensitivity to light
- Elevated body temperature, which can progress to dangerous overheating at high doses
- Jaw clenching and teeth grinding
- Dry mouth and reduced appetite, sometimes to the point of going an entire day without eating
- Tremors or restlessness, particularly in the hands
These effects intensify with higher doses. At lower amounts, you might just feel alert and slightly wired. At higher doses, the heart pounding becomes uncomfortable, breathing quickens, and the line between energized and anxious starts to blur.
The Comedown
The crash after speed is one of its most defining features. Once the drug wears off, your brain has depleted its reserves of dopamine and norepinephrine, and it takes time to rebuild them. The result is essentially the mirror image of the high.
In the first one to three days, most people experience exhaustion, depressed mood, and excessive sleep (often of poor quality). Irritability and agitation are common, and many people report a strong craving to take more of the drug just to feel normal again. Appetite comes roaring back.
Over the following week to ten days, symptoms broaden. Headaches, body aches, mood swings, difficulty concentrating, and trouble sleeping are typical. Some people experience paranoia during this window, feeling judged or watched by others. Vivid, unpleasant dreams are also frequently reported. For heavy or regular users, lingering fatigue, cravings, and emotional instability can stretch on for several weeks to a month after stopping.
When the High Turns Dark
Not everyone experiences speed as purely pleasant, even during the high itself. Anxiety and paranoia are common side effects, particularly at higher doses or after being awake for extended periods. Some people feel agitated rather than euphoric, or find their racing thoughts become overwhelming rather than exciting.
With sustained or heavy use, the psychological risks escalate sharply. Prolonged exposure to high doses can trigger a paranoid, delusional psychotic state that includes auditory and tactile hallucinations. This condition has occasionally been misdiagnosed as schizophrenia. It typically emerges during binge patterns, where someone takes the drug repeatedly over several days without sleeping. The paranoia often comes with intense fear and anxiety, which can drive aggressive or reckless behavior.
One particularly concerning pattern: once someone has experienced stimulant psychosis, it tends to appear earlier and more easily during future binges. The brain becomes sensitized to it. The good news is that these symptoms usually resolve within days of stopping the drug, though that window can feel extremely distressing.
What Chronic Use Does to the Brain
Over time, regular speed use physically changes brain structure. Brain imaging studies of chronic methamphetamine users have found an average 11.3% reduction in gray matter in regions responsible for emotional regulation, decision-making, and impulse control. Hippocampal volume, critical for memory, was nearly 8% smaller than in people who had never used the drug.
At the chemical level, the brain’s dopamine recycling system gets damaged. Chronic users show significantly lower levels of dopamine transporters in key brain regions, meaning the system responsible for normal motivation, pleasure, and reward becomes less efficient. This is why long-term users often describe feeling flat, unmotivated, and unable to enjoy things that used to bring them pleasure. Some recovery occurs with sustained abstinence, but the timeline varies and full restoration isn’t guaranteed.
White matter, the brain’s communication wiring, also changes. Studies have found roughly 7% increases in white matter volume among chronic users, likely reflecting inflammation and the brain’s attempt to repair damage to surrounding neurons. These structural shifts help explain why quitting after heavy, long-term use involves not just willpower but genuine neurological recovery.