Cannabis changes your body through the endocannabinoid system, a receptor network that helps regulate mood, memory, appetite, pain, and sleep. THC, the main psychoactive compound, binds to CB1 receptors in the brain and nervous system, while CBD interacts with the same system in more indirect ways. The result is a recognizable set of short-term effects, plus longer-term risks that rise with dose, frequency, and age of first use.
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What does cannabis do to your body right after use?
Within minutes of inhaling, THC reaches the bloodstream and crosses into the brain. Heart rate climbs, blood vessels in the eyes widen, and saliva production drops, which is why red eyes and dry mouth are common. Many users report relaxed mood, sharper sensory experience, and a slowed sense of time.
Appetite usually increases and nausea can ease, which is why cannabis-derived medicines are prescribed for chemotherapy-related vomiting. Coordination and reaction time drop at the same time, so driving after use is unsafe.
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How does cannabis affect the brain and memory?
THC disrupts the hippocampus, the region that forms new memories. Short-term memory lapses, wandering attention, and trouble following a conversation are typical signs. These effects fade as the drug clears, but heavy daily use is tied to memory and attention problems that outlast the high.
Adolescent brains are still building reward and memory circuits, so early, frequent use carries a higher risk of lasting changes. CBD does not produce the same intoxication, and it may soften some of the cognitive effects of THC, though research is still developing.
What does cannabis do to the heart and blood pressure?
Cannabis can raise heart rate by 20 to 50 percent for up to three hours after use. Blood pressure often drops when standing, which causes dizziness or fainting. For people with existing heart disease, that extra strain can trigger chest pain or, in rare cases, a heart attack.
How does cannabis affect the lungs?
Smoking cannabis delivers many of the same combustion irritants as tobacco smoke, including tar and carbon monoxide. Chronic smokers report more coughing, wheezing, and bronchitis symptoms than nonsmokers. Vaping avoids combustion but is not risk-free, and vitamin E acetate in unregulated cartridges has been linked to severe lung injury.
What about the stomach, sleep, and hormones?
Long-term, high-dose use can cause cannabinoid hyperemesis syndrome, marked by repeated vomiting and abdominal pain that hot showers briefly relieve. Heavy use also suppresses REM sleep, leaving users feeling unrested even after a long night. Hormone shifts can include lower testosterone in some men and disrupted ovulation in some women.
How long do the effects last?
Inhaled cannabis peaks within 10 to 30 minutes and tapers over two to three hours. Edibles absorb slowly, so they peak at two to four hours and can last six to eight hours or more, which makes overconsumption easy. Effects on judgment and reaction time can outlast the felt high.
What changes how cannabis affects you?
- Dose and the THC-to-CBD ratio
- Method of use: inhaled, edible, or topical
- Tolerance and how often you use
- Age, body weight, and liver enzymes
- Alcohol, other drugs, or prescription medicines
- Genetics and prior experience
What are the risks of long-term use?
Daily use raises the odds of cannabis use disorder, tolerance, and withdrawal symptoms such as irritability, insomnia, and reduced appetite. Heavy use is linked to anxiety and paranoia, and in some people, psychosis, with the highest risk among those who have a family history. Cannabis smoke also carries cardiovascular and respiratory risk that grows with years of use.
When should you talk to a doctor?
Speak with a clinician about chest pain, fainting, ongoing vomiting, worsening anxiety or paranoia, or trouble cutting back. Legal cannabis in the US is not the same as risk-free cannabis, and a doctor can help you weigh effects against interactions with your medications. This guide is educational and not medical advice.