Short answer: Cannabis is a plant whose main psychoactive compound is THC. Adult-use (recreational) cannabis remains Schedule I under federal law, but in April 2026 marijuana in state-licensed medical programs and FDA-approved cannabis products moved to Schedule III. Most states allow medical use and about half allow adult use. Cannabis can cause dependence, psychosis in some users, and a severe vomiting syndrome.
Key takeaways
- What it is: Cannabis is a cannabinoid (plant) and a Schedule I controlled substance in the US.
- Medical use: State medical programs; FDA-approved cannabinoids.
- Timing: effects start in minutes (inhaled); 30 minutes to 2 hours (edibles) and last 2 to 8 hours.
- Most dangerous mix: Alcohol, which can cause stronger impairment; more vomiting and dizziness.
- Naloxone: it does not reverse this drug, but give it whenever opioids could be involved.
- Dependence risk: Moderate.
- Legal route: none. Schedule I substances cannot be prescribed.
What is cannabis?
Cannabis refers to the dried flowers, leaves, and extracts of the Cannabis sativa plant. THC activates cannabinoid receptors in the brain, producing a high. CBD does not cause a high and has different effects.
Cannabis can cause relaxation, euphoria, altered perception of time, increased appetite, red eyes, dry mouth, and a faster heartbeat. It also impairs short-term memory, coordination, and reaction time.
Quick facts
| Fact | Cannabis |
|---|---|
| Main compounds | THC (psychoactive), CBD (not intoxicating) |
| Common names | Marijuana, weed, pot, bud; concentrates: wax, shatter, dabs |
| Drug class | Cannabinoid |
| US legal status | Adult-use: Schedule I; state-licensed medical and FDA-approved products: Schedule III (since April 2026) |
| FDA-approved products | Epidiolex (CBD, not controlled); dronabinol and nabilone (synthetic THC and analog) |
| How it is used | Smoked, vaped, eaten, or drunk |
| Onset | Minutes (inhaled); 30 minutes to 2 hours (edibles) |
| Duration | 2 to 4 hours (inhaled); 6 to 8 hours or more (edibles) |
| Half-life | THC: about 1 to 3 days in occasional users; longer in daily users |
How long does cannabis last?
- Starts working: Minutes (inhaled); 30 minutes to 2 hours (edibles)
- Effects last: 2 to 8 hours
- Half-life: THC: about 1 to 3 days in occasional users; longer in daily users
Occasional users usually test positive for 3 to 7 days; daily users can test positive for 30 days or more.
Timing varies with the dose, the form, how it is taken, liver and kidney function, age, and other drugs taken at the same time.
What are the biggest risks of cannabis?
Cannabis use disorder: about 3 in 10 people who use cannabis have some degree of cannabis use disorder. The risk is higher with daily use, high-potency products, and use that starts before age 18.
Mental health: high-potency cannabis is linked to a higher risk of psychosis and schizophrenia, especially with heavy use in teens and young adults and in people with a family history.
Cannabinoid hyperemesis syndrome: some long-term heavy users develop repeated bouts of severe vomiting and abdominal pain, often relieved by hot showers. It only resolves by stopping cannabis.
Warning: Edibles that look like candy or snacks have caused many emergency visits in young children. Store them locked away and call Poison Help at 1-800-222-1222 if a child eats one.
What should you never mix with cannabis?
| Combined with | What happens | Risk level |
|---|---|---|
| Alcohol | Stronger impairment; more vomiting and dizziness | Higher risk of accidents |
| Sedatives, opioids, sleep medicines | Additive drowsiness | Use caution |
| Psychedelics | More intense or frightening experiences | Use caution |
| Warfarin | THC and CBD can raise warfarin levels | Monitor INR |
| Clobazam, valproate (with CBD) | CBD raises levels; liver effects | Medical supervision |
Check any combination with the DoseUses combination checker or ask a pharmacist.
What are the signs of a cannabis overdose, and what should you do?
Fatal overdose from cannabis alone is extremely rare in adults, but taking too much can cause severe anxiety and panic, paranoia, vomiting, a racing heart, confusion, and, rarely, psychosis. Children who eat edibles can become very drowsy, have trouble breathing, or have seizures and need emergency care.
If someone has taken too much
- Call 911 for chest pain, a seizure, trouble breathing, unresponsiveness, or if a child may have eaten a cannabis product.
- For an adult who is awake but anxious or sick, move them to a calm place and stay with them. Symptoms usually ease over several hours.
- Call Poison Help at 1-800-222-1222 for advice, including for any child or pet exposure.
- Do not drive. Edibles can keep building for hours after they are eaten.
Is cannabis addictive, and what is withdrawal like?
Regular use can cause dependence. People who use daily often feel withdrawal when they stop.
- Days 1 to 3Symptoms beginIrritability, anxiety, trouble sleeping, reduced appetite.
- Days 2 to 6PeakVivid dreams, restlessness, low mood, cravings, sweating.
- 1 to 2 weeksResolvesMost symptoms fade; sleep can take longer to normalize.
See the withdrawal timelines and the full cannabis withdrawal guide.
Is cannabis legal?
Federal law (2026): on April 22, 2026, the Justice Department moved FDA-approved products containing marijuana, and marijuana produced and sold under state-licensed medical marijuana programs, from Schedule I to Schedule III. Adult-use (recreational) marijuana remains Schedule I. A separate DEA hearing on rescheduling all marijuana ended in July 2026, and a decision was pending as of October 2026.
- Possession: under federal law, a first conviction for possessing any controlled substance without a valid prescription can bring up to one year in prison and a minimum fine of $1,000. Penalties rise with prior convictions.
- Selling or sharing: distribution carries much heavier federal penalties, which increase with the amount involved and are higher still if the drug causes death or serious injury.
- State law: states set their own penalties, and most drug cases are prosecuted under state law. Penalties range from a civil fine to long prison terms depending on the state, the amount, and prior record.
Outside the United States
| Country | Status |
|---|---|
| Canada | Legal for adults since 2018 under the Cannabis Act |
| Uruguay | Legal for adults since 2013 |
| Germany | Legal for adults to possess and grow limited amounts since 2024 |
| United Kingdom | Class B; medical cannabis by specialist prescription since 2018 |
| International | Schedule I of the 1961 Single Convention (removed from Schedule IV in 2020) |
Frequently asked questions about cannabis
Is marijuana Schedule III now?
Partly. Since April 2026, marijuana in state-licensed medical programs and FDA-approved products are Schedule III. Adult-use marijuana is still Schedule I while a broader decision is pending.
Is cannabis addictive?
It can be. About 3 in 10 people who use cannabis have some degree of cannabis use disorder, and daily users often have withdrawal when they stop.
How long does THC stay in your system?
Occasional users usually test positive for 3 to 7 days; daily users can test positive for 30 days or more.
What is cannabinoid hyperemesis syndrome?
Repeated severe vomiting in heavy long-term users, often eased by hot showers. It goes away only after stopping cannabis.
Is delta-8 THC legal?
Under a 2025 federal law, intoxicating hemp products such as delta-8 THC become federally illegal on November 12, 2026, and many states already ban them.
Can you drive after using cannabis?
No. Cannabis slows reaction time and impairs coordination. Driving under its influence is illegal in every state.
Sources
- Cannabis (Marijuana), National Institute on Drug Abuse.
- Cannabis and Public Health, Centers for Disease Control and Prevention.
- Rescheduling of FDA-approved products containing marijuana and state-licensed medical marijuana to Schedule III, Federal Register, April 28, 2026.
- New federal restrictions on hemp and hemp-derived products, DLA Piper, November 2025.
- 21 U.S.C. 844, Penalties for simple possession, Legal Information Institute, Cornell Law School.
- 21 U.S.C. 841, Prohibited acts A (trafficking penalties), Legal Information Institute, Cornell Law School.
- National Helpline, Substance Abuse and Mental Health Services Administration.
- FindTreatment.gov, Substance Abuse and Mental Health Services Administration.
This guide summarizes the sourced DoseUses Cannabis profile, written from FDA labels, DEA rules, and federal health agencies. It is educational and is not medical advice. Last updated October 5, 2026.
