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- 🔀 1 in 5 adults aged 18–25 report mixing cannabis and alcohol during the same occasion.
- 🧠 Using substances at the same time can hide alcohol’s bad effects, causing people to drink more.
- ⚠️ People with Alcohol Use Disorder drink more often and in higher amounts when mixing with cannabis.
- 🚗 Mixing cannabis and alcohol makes blackouts, accidents, and bad decisions much more likely.
- 📊 Health campaigns rarely talk about the risks of using both at once, even though it’s happening more often.
Mixing cannabis with alcohol might seem like a way to feel the effects more or make drinking side effects easier. But recent studies show this mix might actually make people drink more, not less. Since cannabis is legal in many states and more accepted socially, using both substances at the same time is going up, especially among adults aged 18–25. But what happens when cannabis makes alcohol’s warning signs less clear? And how does this affect people already struggling with Alcohol Use Disorder (AUD)? Let’s see what science is finding about mixing these substances.
What Is Simultaneous Substance Use?
Simultaneous substance use (SSU) means using two or more substances that affect your mind close together in time, so their effects overlap. When we talk specifically about cannabis and alcohol, SSU usually means using both during the same event or time – for instance, smoking cannabis while drinking a cocktail, or using a cannabis vape between rounds of beer.
This is different from just using both at separate times, like in the same week or month. Using them separately doesn’t necessarily cause effects that work together, but SSU often causes chemicals to react in the body and brain.
Numbers from the 2022 National Survey on Drug Use and Health show that about 20% of adults aged 18–25 use alcohol and cannabis at the same time. This group is concerning. They are at a stage where they are still developing, and mixing substances could cause long-term problems with dependence and brain health.
SSU is not just something people do for fun. It’s a behavior that affects health and can have medical results.
Why Legalization Matters for How People Use Substances
As cannabis becomes legal and more normal across many states in the U.S., how people use it is changing fast. Before, cannabis was illegal, and this made it harder to mix substances. But now, dispensaries are everywhere, and the social situation is different.
Legalization has changed simultaneous use in these main ways:
- Easier to get: It’s easier than ever to get cannabis. This is true for things like edibles and vape pens, which you can use easily without others noticing in social places.
- Normal in social places: People don’t see cannabis as something outside the norm anymore. You often find it in places where people drink alcohol, like bars with cannabis areas, music festivals, college parties, or other social gatherings.
- Feeling safe when it’s not: Since it’s legal and sold as medicine or for well-being, some users think cannabis is safe. This is true even when they mix it with alcohol, which slows down the brain and body.
Young adults and college students are more likely to follow trends of using both. They might do it as part of binge drinking or to deal with problems. Because of legalization, it’s harder to tell the difference between just having fun and doing something risky when mixing cannabis and alcohol.
What Studies Show About Using Both at Once
Scientists are still studying simultaneous cannabis and alcohol use. But what they have found so far is clear: mixing these substances raises the risks right away and over time.
More studies show SSU affects behavior and the body in these ways:
- Drinking more: People who mix cannabis and alcohol often drink more when they do it.
- Feeling less drunk: Cannabis can make people feel less drunk. This causes them to keep drinking more than they normally would.
- More likely to get hurt: People who do SSU are much more likely to black out, do risky things, and face problems from alcohol like DUIs or getting injured.
One important study published in Addictive Behaviors in 2021 found that people who did SSU said they had more memory problems, missed responsibilities, and had legal issues. This was more than people who only drank alcohol. This shows how cannabis (which often makes you relaxed) and alcohol (which often makes you do things you wouldn’t normally) work against each other. It can make people think they are less impaired than they really are.
Simply put, SSU makes you ignore your body’s signals. This can lead to behaviors that could be dangerous.
How People Feel Less Harmed: Why?
When you only use alcohol, bad side effects usually tell you to stop. Things like feeling sick, dizzy, slow, or tired are warning signs. But cannabis makes these signs feel less strong.
This effect that hides the signs makes things worse for:
- Knowing how your body feels: Feeling less drunk makes people keep drinking even when they have a high amount of alcohol in their blood (BAC).
- Stopping yourself: Alcohol makes it harder to make good choices. Cannabis can quiet the worry or doubts that might normally protect you.
- Feeling able: Some users say they feel more “in control” or “less drunk” when they mix cannabis and alcohol. This makes them more willing to drive or take other risks.
The American Psychological Association showed in 2024 that people who think their substance use is not that bad are more likely to use more or more often. This feeling of safety that isn’t real makes SSU very dangerous.
It’s not just about how you feel—it’s about what’s happening in your bloodstream and your brain.
Alcohol Use Disorder (AUD) and Why Mixing Cannabis and Alcohol is More Dangerous
More than 14 million adults in the U.S. have Alcohol Use Disorder, or AUD (NIAAA, 2023). This is one of the biggest health problems the public faces. When people with AUD start adding cannabis to their drinking, it can make their disorder much worse.
Recent studies looked at how people with AUD use both cannabis and alcohol. They found:
- Drink more often: People with AUD who use cannabis tend to drink more days each week.
- Drink more in one go: When cannabis is used, people drink more alcohol during one drinking time.
- Treatment doesn’t work as well: People trying to stop drinking might have trouble if they keep using cannabis. This is especially true if they use cannabis at important social times.
Why does this happen? People with AUD might use cannabis thinking it will help them drink less or control their drinking. But this usually doesn’t work. Cannabis might not replace alcohol. Instead, it can make people drink for longer periods and stop them from holding back.
It’s very important to know this happens so that treatment plans for people with AUD can be made right for them.
What’s Happening in the Brain?
Both alcohol and cannabis change important parts of the brain. These parts handle reward, stopping yourself, controlling your mood, and making choices. These effects happen mostly because they change how brain chemicals, called neurotransmitters, work:
- Dopamine: Both make the brain’s reward center release more dopamine. This creates a good feeling the brain wants to have again.
- Endocannabinoids: The THC in cannabis acts like natural chemicals the brain makes. This changes mood and pushes down bad feelings.
- GABA and glutamate: Alcohol makes GABA work more (this brain chemical calms you). It also stops glutamate from working as much (this one excites you). This slows down how the brain works.
When used together, these effects create a strong cycle. Cannabis can make you less aware of how drunk you are. And alcohol makes it even harder to make good choices and control what you do. Over time, making these reward centers in the brain too active might lead to:
- Less drive to do things
- Problems with thinking clearly and planning
- A higher chance of becoming dependent on substances
Brain scans show changes in brain structure and how different parts work together in people who use both often. These changes are especially seen in brain areas that help control behavior.
Why People Mix Them in Social Settings
Being with others often makes people take more risks, especially young people. Being “cross-faded” (high and drunk at the same time) is often seen as cool by friends and on social media. When this becomes normal, people don’t see the total harm that builds up from using both.
Things that make friends influence SSU include:
- Social habits: Drinking and smoking together feels like a way to connect in many young people’s groups.
- Feeling safe because others are doing it: Being in a group makes people feel safe, even if everyone is impaired.
- What people expect: If others look okay mixing substances, people are more likely to do the same without thinking about the risks.
For teens and college students, whose brains are still growing, the risk is even bigger. Doing SSU often can mess up how their brains finish developing and how they handle emotions.
What Are the Risks?
The effects of cannabis and alcohol together make the risks much bigger:
- Binge Drinking: Cannabis use removes the “off-switch” queasiness that usually stops someone from bingeing.
- Blackouts: You are more likely to black out from alcohol when doing SSU.
- Bad Choices: A higher chance of having unsafe sex, starting fights, or driving while impaired.
- Getting Hurt: Slow reaction time and not moving well make you much more likely to fall or have accidents.
- Stomach Problems: Putting too many things that slow down your body into your system makes you more likely to feel sick, dizzy, and throw up. People call this “greening out.”
- Organ Damage Over Time: Using both often can make liver damage happen faster and cause problems with thinking.
These dangers don’t affect everyone the same way. People who already have mental health issues or substance use disorders are much more likely to have bad results.
Why This Can Be Hard to Treat
Treating AUD needs special help. This often includes talking therapy, medicine to help, and watching over the person for a long time. But many treatment places don’t check carefully for cannabis use. They might think it’s “less harmful.”
Having cannabis involved makes things harder for:
- Chance of going back: Cannabis might make people want alcohol again. This is because they might use both in social or stressful situations.
- Clear goals for treatment: People getting help might think just stopping alcohol is enough. They might not realize how much cannabis is also a problem.
- How medicines work: Cannabis can affect medicines for AUD, like naltrexone or disulfiram. This might make the medicines not work as well.
It’s key to check for everything and make treatment plans that deal with both substances at the same time. Doctors and therapists need training to spot patterns of using both substances together. They shouldn’t just look for alcohol abuse by itself.
Public Health and Policy Concerns
Even though it’s legal, cannabis still doesn’t have good rules around it in places where people drink alcohol. Few state or federal rules explain clearly the risks of SSU. So:
- Programs meant to stop substance use usually talk about alcohol or cannabis, but not both.
- Rules at work might have punishments for alcohol use. But the rules for cannabis are often unclear.
- Police and traffic laws find it hard to test if someone is impaired by cannabis right away. This makes it tough to make people follow DUI laws for mixing substances.
More people are using both, so public rules need to change. Campaigns should talk about what happens when cannabis and alcohol are mixed. And healthcare workers need clearer instructions on how to check for this and teach people about it.
What We Need to Study Next
We really need studies that follow people over a long time to see:
- How it affects the brain: What happens to brain development when people use both for a long time?
- Gene-based risks: Are some people more likely to get substance use disorders from SSU because of their genes?
- How well does treatment work for using both? What kinds of programs work well for people who depend on both alcohol and cannabis?
- Effect on society: What happens to public safety, healthcare costs, and young people when many people do SSU?
Focusing research can help us know what to do early on. It can also help make treatment plans better for people who use many substances.
What You Can Do: Advice for Doctors, Nurses, and Everyone Else
Whether you’re a healthcare provider, a parent, or someone who uses cannabis and alcohol, there are steps you can take to reduce harm:
- Regular checking: Ask simple questions about how and how often people use both alcohol and cannabis.
- Teach others: Give correct information about the risks, and do it in a way that doesn’t judge people.
- Spot problems: Look for people doing SSU often, especially when they are stressed or at parties.
- Send people to treatment that helps with both: Treatment works better when it deals with both substances at the same time.
- Talk about other ways to cope: Things like mindfulness, certain types of therapy (CBT), or support from others might help people rely less on SSU.
Knowing about this is the first step to being safe and doing well.
Proceed Carefully When Mixing Substances
Cannabis may make alcohol feel smoother, less nauseating, or more socially pleasant—but that doesn’t mean it’s safer. Actually, the things that make mixing cannabis and alcohol seem good are the same things that can lead to drinking a lot and causing harm over time. This is especially true for people who are already likely to become addicted.
As social settings change and legalization is common, knowing how these substances work together is very important. This is true for people themselves, their families, and the people who work with them.
Citations:
- American Psychological Association. (2024). Trends in high-risk drinking and cannabis use.
- MacKillop, J., & Murphy, J. G. (2021). Simultaneous cannabis and alcohol use elevates risk of substance-related harm. Addictive Behaviors, 122, 107009.
- National Institute on Alcohol Abuse and Alcoholism. (2023). Alcohol facts and statistics. https://www.niaaa.nih.gov/publications/brochures-and-fact-sheets/alcohol-facts-and-statistics
- Substance Abuse and Mental Health Services Administration. (2022). National Survey on Drug Use and Health.