These questions were answered by more than 50 individual scientists and science writers with expertise in addiction. To get as many answered as possible, responses were written quickly based on the personal background and knowledge of each expert. Please note that there was not a secondary review or proofreading of each fact, and if readers have questions or comments about any response, they can ask further questions.

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How can you tell if someone is doing drugs? What are the effects that we will see?

-Toribio, California

Hi Toribio. Sometimes it's really obvious when someone has been drinking or smoking--they may smell or show obvious intoxication. But sometimes people hide their behavior and it's hard to detect. More subtle signs are being absent from events with family and friends, changes in emotions (like anger or surprising giddiness), changes in school performance, or changes in friends. Here's a link to information about drug use in teens:

-Wilson Compton

how can you tell if someone is high

-#externalharddr, Illinois

It depends on what drug the person has taken. Stimulants like cocaine or meth might cause someone to be very twitchy and talkative, while opioids may cause a person to be unusually relaxed. Slurred speech, lack of coordination, and especially big or small pupils are other signs of recent drug use.

-Tisha Wiley

How can you tell if someone is overdosing?

-DW, Washington

Hi, dwatkins@masd20! Symptoms of drug overdose include nausea, vomiting, abdominal cramps, dizziness, loss of balance, and seizures. If you see any of these symptoms and you believe that the person has been taking drugs, please seek help as soon as possible. Call 911 and let an adult know.

-Roger Sorensen

how can you tell someone has been using weed? are the signs you can see in order to avoid getting in a car with a high driver?

-eloise, Illinois

Good question! It's not always easy to tell if someone is using marijuana. Marijuana use speeds up a person's heart rate, enlarges the bronchial passages (the pipes that let air in and out of your lungs), and expands blood vessels in the eyes, making the eyes look red. While these and other effects seem harmless, they can take a toll on the body. Marijuana use can also impact a person's ability to make good decisions as well as impact their coordination and driving, so if you are concerned about someone's ability to drive safely, definitely pass on that ride!

-Michele Rankin

how can you tell someone has taken drugs in school

-LA, New Hampshire

Hi, Lily. You might not be able to always tell, but if someone has taken enough of a drug it can affect their behavior. Marijuana use can sometimes be discerned by red eyes, stimulant use (even caffeine) can be indicated by jittery behavior. Withdrawal from drugs can also generate changes in behavior and emotions.

-Ruben Baler

how can you tell someone is depressed

-what the nugget, Illinois

Hi Nugget,
There are a few common symptoms of depression that you can look out for. Some of these include not getting happy from things that usually make you happy, not being motivated to do anything, and feeling unusually sad for extended periods of time (over 2 weeks). However, it can be difficult to tell if someone feeling like this is depressed or is just responding to the normal stress in their life. If you aren't sure if you or someone you know might be depressed, it could be worth you or them talking to a school counselor or trusted adult who might be able to give more personalized advice. You can also check out our Teen Depression brochure, here:

-Eric Murphy

how can you treat an addiction that is not related to substance use?


Hi Ic
great questions
There are many so caled "behavioral" addictions, from obesity, to gambling, to sex addicts. In some instances we have identified significant overlaps in the brain circuits impacted by drug and behavioral addictions, so treatment modalities may also overlap in some cases. But these conditions have to be first diagnosed and then treated by a mental health doctor specialized in the specific condition we are talkig about. Talk to your primary care doctor if you know someone suffering from any of these conditions. or call SAMHSA 1 800 273 8255

Best of luck

-Ruben Baler

How come it's legal for weed to be in california now?

-Messi, Illinois

Hi Messi, good question. Some states do allow medical and recreational use of marijuana, but it is still illegal according to the federal goverment. It is important to remember that it is not safe for teens to use marijuana, since the brain is not fully developed until you are in your mid-20s. Check out more info here: Marijuana: Facts for Teens booklet:

-Emily Jones

How come people see it's a great idea to snort cocaine?

-DJ, New Hampshire

Hi Darcie Jackson! Cocaine gives people a burst of energy and euphoria. Unfortunately, when that wears off they feel bad and want to use the drug again. It definitely is not a good idea to snort cocaine!

-Michelle Leff

how come people take these drugs if they know it can kill them? What is so addicting about these drugs even though they taste bad?

-Skye, Illinois

People do drugs for lots of different reasons. Some people do it to impress people. Some people do it to feel good in the moment, kind of like eating junk food, without thinking about the consequences. But the effect of using drugs - any drugs - on your brain and body can be severe, especially if you start using drugs when you are a kid or in your teens. There is a lot of information about the health effects of drugs on NIDA's teen site here: Addiction is complex and often driven by changes in your brain. This video is a good resource for helping to understand: Why Do Some People Get Addicted? See the Swiss Cheese Model of Drug Addiction:

-Tisha Wiley

How come weed is legal in Canada but not in the u.s

-Smoke Weed, Illinois

Because the Prime minister who was elected in Canada ran on a platform that included marijuana legalization. The US is abiding by an International Treaty that keeps it illegal, but allows research to determine its potential medical benefits.

-Susan Weiss

How damaging is weed to underage people

-Pajamadunes, California

Good question. Check out this website for a lot of good info on this topic:

-Steve Gust

how dangerous are opiods, they get prescribed by doctors, right

-not el chapo, Illinois

Great question! All drugs can be dangerous - it depends on several things, including how you take them and how much you take. Opioids attach to receptors in your brain, causing a large amount of a neurochemical called dopamine to be released. The release of dopamine into your body can make you feel relaxed and pain-free. This is why opioids are important in the treatment of intense pain, for example. Doctors prescribe opioids when it is appropriate for the treatment of the problem their patient is experiencing. However, misuse or overuse of opioids can cause harmful effects like extreme sleepiness, confusion, nausea, vomiting, and constipation. Over time, opioid use can lead to insomnia, muscle pain, heart infections, pneumonia, and addiction. It is important to take medications like opioids only under the direction of health care provider and in the way they prescribe them. For more, visit:

-Michelle Jobes

how dangerous are the hard drugs like Xanax Cocaine and aderal

-Big Daddy , Illinois

Hi Big Daddy,
Using drugs, any drugs, is really a bad idea in general, but an especially bad one for young people, whose brains are still developing, so that the negative effects can last a very long time. So much smarter to stay away...
B smart!

-Ruben Baler

how dangerous are tobacco cigarretes?


Hi there. Thanks for your great question. Cigarette smoking is the most preventable cause of cancer in the United States. Smoking cigarettes has been linked to cancer of the mouth, neck, stomach, and lungs, among others. Nonsmoking people exposed to secondhand cigarette smoke increase their chances of developing lung cancer in addition to other health problems. For more information see:

-Jacqueline Lloyd

How dangerous is getting drunk?

-wmsboi101, Illinois

Hi wmsboi101,
Alcohol is like other drugs in that its effects are proportional to the amount consumed. There is a lot of variability between people in how their body and brain respond to alcohol. Remember in the U.S., it's not legal for anyone under the age of 21 to drink alcohol.
Alcohol results in people feeling high or drunk, and can also cause impairment - slowing your reflexes, performance and judgement. Drinking alcohol in large amounts can also cause alcohol overdose and lead to death. For more information click here: Alcohol Overdose
Hope this helps!
- Vijay

-Vijay Ramchandani

How dangerous is Ketamine?

-Mateo ,

Hi Mateo- thanks for asking about Ketamine! Ketamine (also known as cat valium, k-hole, and purple) is a dissociative anesthetic. That means it distorts perceptions of sight and sound, and makes a person feel detached from their environment and themselves. It also reduces pain and overall feeling. Like other anesthetic drugs, it's used during surgical procedures in both humans and animals. Carefully monitored, under a medical doctor's care, it is safe. Be safe and don't use Ketamine as a recreational drug. For more informations see:

-Mary Kautz

How dangerous is marijuana?

-Jimmy John Jr, Illinois

Hi Jimmy John. Thanks for your question. Because teens brains are still developing any drug use poses dangers for teen. Marijuana can cause problems with learning and memory leading to problems in school; it can have an effect on how well you are able to drive a car, and the effects are heigtened when you pair that with drinking. Chronic use of marijuana is also linked to increased chance for mental illness and increase your risk to abuse other drugs. Want more info on the effecs of marijuana? Click here -

-Marsha Lopez

how dangerous is xanax

-not el chapo, Illinois

When prescribed by a doctor, Xanax can be safe. But there are side effects (like sleepiness and motor impairments) that need to be monitored. There is also a risk of addiction if Xanax is used for longer periods of time. Also, Xanax can be very dangerous when taken with other drugs, especially alcohol -- it can raise the risk of overdoses and other harms. So it is dangerous to use on your own.

-Joshua Gordon

how did drugs become considered "cool"

-mtiemann20, Oregon

hi mtiemann20
I am not sure i can give you a scientific answer for your question. I can speculate though that sometimes young people tend to follow their peers, and something that is objectively and categorically stupid or silly (think about the Tide pod challenge!!!) becomes a popular fad. Maybe it has to do with the tendency of young people to take risks combined with a strong urge to belong. That combination sometimes makes us do stupid things and call something cool just to fit in, even if we know deep down that's just no so.
hope this is helpful

be smart. b cool.

-Ruben Baler

how did weed come into the world

-RS, New Hampshire

Hi Riley
Such a good question,
It's not just weed, ther are many natural products in the world that just happen to have the ability to affect our mind and body. These effects are likely the unintended consequence of another (mostly unknown) biological property, like repelling insect or managing stress. Some such compounds are actually good and have helped us develop potent medications (e.g., penicillin), some are double edge swords (think how opium can help manage pain but also cause addiction and death). There are many toxic and poisonous things out there, we just need to identify them and protect ourselves. In the case of weed, arm yourself with information and respect your brain, keeping its development free from marijuana or any other drug.

-Ruben Baler

HOW did you get in STEM Field


I met a rat stimulating its reward system with an electrode in 1969 and wanted to know what was the brain neurocircuitry of reward ( feeling good). Subsequently, I have spent the latter half of my career trying to understand the neurocircuitry of feeling bad :-)

-George Koob

how did you get in the STEM Field?

-Aybrian-FVSU4H, Georgia

Hi Aybrian,
I always liked science (and baseball). And one day, in a bowling alley, a friend that was starting college, told me about what he was learning about the brain in class. I found it amazing how the brain works. I knew I wanted to learn more about how brains work and studied it in college and beyond. I followed that dream, and now, here I am at Chat Day writing about drugs and the brain!

-Dave Thomas

how did you learn about background of drugs and many causes from them

-whitney-FVSU4H, Georgia

I learned about drugs and their effects on the brain and body when I went to school to get my PhD in neuroscience.

-Emily Einstein

HOW did you learn about the background of drugs and many cause form them

-Angela-FVSU4H, Georgia

Hi Angela
I am glad you asked that.
we have different ways for investigating the effects of drugs. Some studies are done on single cells (this are called basic research). Other studies (preclinical) use animals; these allow us to test the effects of drugs on behavior and physiology in highly controlled environments and ask questions that would be impossible to ask in humans. Other studies (so called clinical) studies can be done directly in humans. These are more constrained because of safety and ethical considerations and because there are so many variables that we cannot control, but these are closer to reality and extremely useful, particularly for the development of effective addiction treatments.
hope this helps.

-Ruben Baler

How do "addiction" and "dependence" relate to each other?

-Brendan, Illinois

Hi Brendan! Addiction happens when a person feels compelled to take a drug, despite bad things happening physically, emotionally, or socially to them when they use it. Dependence refers to when a person experiences withdrawal when they stop taking a drug. It is possible to be dependent on a drug, but not be addicted. (If one is addicted, they are most likely dependent as well.) For example, a person may be treated with the opiate morphine long-term if they have terminal cancer. They may become dependent on it even when taking it as prescribed. However, when it's time to stop, they would feel withdrawal symptoms, but not feel compelled to take the drug. They are dependent, not addicted. Finally, people treated with morphine in the hospital for pain after surgery may feel some euphoria, but pain relief and sedating effects prevail - no compulsive use and prescribed use is short-lived.

-Michelle Jobes

How do criminals obtain such dangerous substances without being caught by our Nation's Justice system?

-Jac, Maryland

Great question! Our country's law enforcement professionals all work very hard to try to catch people who produce and distribute drugs in this country. But their job is really hard! Some very dangerous drugs like fentanyl are very potent and thus come in very small packages that can be hard to find. People who buy and sell drugs are very motivated to keep these activities concealed from law enforcement.

-Susan Weiss

How do dealers get access to large amounts of drugs like fentanyl and or other prescription drugs if they are only available by prescription or at the hospital?

-Kat, Maryland

Hello Kat,

Great question!
Most of the illegal fentanyl that is distributed by drug dealers are not pharmaceutical grade (i.e., they are not made by pharmaceutical companies). They make this fentanyl in their own labs and it can be mixed with heroin or cocaine, which markedly amplifies its potency and potential dangers. For more information, check out

-Aaron White

How do different drugs affect you when mixed with alcohol.

-alewine01, Oregon

Alcohol interacts with a wide range of drugs. It is particualrly dangerous to combine alcohol with other drugs that are sedating, or make people feel sleepy. Such drugs include the opioids and the benzodiazepines, like valium or xanax. Combining alcohol with these drugs can suppress the brainstem and cause death. Other drugs, like stimulants, can allow people to stay awake and drink more, reaching potentially deadly levels of consumption.

-Steve Gust

How do different drugs effect pregnant women?

-alewine01, Oregon

Hello alewine01,
This is a very complicated question. Drugs can powerfully affect the development of a fetus and they can also affect the woman that is taking them. They can either interfere with natural signaling that is telling the baby how to grow and develop or have toxic effects that harm the baby. Even some prescription drugs can have negative effects on a baby during development. There are more details in at this link:

-Ruben Baler