Cannabis and Alcohol: Understanding the Risks of Mixing

Cannabis and alcohol are the two most widely used recreational substances in the world, and it is extremely common for people to use them together — whether at a party, a concert, or simply during a relaxed evening at home. The combination is so prevalent that it has its own slang term: getting "crossfaded." But despite how common this practice is, most people have a limited understanding of how these two substances actually interact in the body, and why combining them — especially when edibles are involved — carries risks that neither substance presents on its own.

This article is not here to tell you never to mix cannabis and alcohol. For many adults, moderate and informed use of both substances is a personal choice. But understanding the pharmacology behind their interaction, the specific risks involved, and the harm reduction strategies that can minimize those risks is essential for anyone who chooses to combine them. Knowledge is the best form of harm reduction.

How cannabis and alcohol interact in the body

Cannabis and alcohol affect the brain and body through different mechanisms, but their effects overlap and stack, so the combination impairs you more than either substance alone. Alcohol is a central nervous system depressant that works primarily by enhancing the effects of GABA (an inhibitory neurotransmitter) and inhibiting glutamate (an excitatory neurotransmitter). This is what produces the characteristic effects of alcohol: relaxation, lowered inhibitions, impaired coordination, and at higher doses, sedation.

THC, the primary psychoactive compound in cannabis, works through the endocannabinoid system by binding to CB1 receptors in the brain. Its effects include altered perception, euphoria, impaired short-term memory, and changes in motor coordination. When THC is consumed as an edible, it is metabolized by the liver into 11-hydroxy-THC, a compound that crosses the blood-brain barrier more efficiently than THC itself, producing stronger and longer-lasting effects.

A key finding from research is that alcohol can raise blood levels of THC. In a 2015 controlled study published in Clinical Chemistry, participants drank alcohol and then vaporized cannabis. Their peak blood levels of THC, and of its active metabolite 11-hydroxy-THC, were higher than when they took the same cannabis without alcohol; at the higher cannabis dose, median peak THC rose from 42.2 to 67.5 μg/L. A companion analysis found that alcohol also extended how long the cannabis effects lasted. That research used inhaled cannabis. No controlled study has measured how alcohol changes THC levels from edibles, so the size of the effect with edibles is unknown.

In practical terms, assume that a few drinks can make an edible feel stronger than it would on its own, by an amount you can't predict. That uncertainty adds to the edible's already variable absorption and delayed onset, and it is a common reason people end up with more than they bargained for when mixing the two.

The order matters: drinking then edibles vs edibles then drinking

One of the most important factors in how cannabis and alcohol interact is the order in which they are consumed. This is not a minor detail — the sequence can significantly change the nature and intensity of the combined experience, and understanding it is crucial for harm reduction.

Drinking alcohol first, then consuming edibles is generally considered the riskier order. As discussed above, drinking before using cannabis has been shown to raise peak blood THC levels, at least with inhaled cannabis. With an edible, that could mean a more intense experience than the same edible would give on its own. Alcohol also lowers your judgment about whether to take more. Many people describe this sequence as the one that leads to "greening out" — the cannabis overconsumption syndrome characterized by extreme nausea, dizziness, sweating, and sometimes vomiting.

Consuming edibles first, then drinking alcohol presents different risks. Some research suggests that cannabis may slow gastric motility — the rate at which substances move through the digestive system — which could theoretically slow the absorption of subsequently consumed alcohol. Some users report that being mildly high reduces their desire to drink heavily, which could serve as an unintentional form of moderation. However, the opposite can also occur: cannabis can mask the subjective feeling of being drunk, leading people to drink more than they normally would because they do not feel as intoxicated as they actually are. This disconnect between perceived and actual impairment is dangerous, particularly when it comes to decision-making around driving or other risky activities.

The timing gap between consumption also matters. The longer the interval between consuming alcohol and consuming an edible (or vice versa), the less pronounced the interaction tends to be. If you had two beers at dinner and take a low-dose edible three hours later, the interaction will be much milder than if you take the edible while actively drinking. This spacing principle is one of the most practical harm reduction strategies available to people who choose to use both substances.

Short-term risks of combining cannabis and alcohol

The most common short-term risk of combining cannabis edibles and alcohol is the intensification of unpleasant side effects from both substances. The combination frequently produces severe dizziness and a spinning sensation (colloquially known as "the spins"), which can be extremely uncomfortable and disorienting. Nausea and vomiting are also much more common with the combination than with either substance alone, particularly when alcohol is consumed before the edible.

Cognitive impairment is dramatically amplified when cannabis and alcohol are combined. Both substances independently impair reaction time, attention, memory, and decision-making, and together their impairments add up. In a 2015 driving-simulator study, cannabis and alcohol effects on lane weaving were additive. A blood THC level of 5 μg/L combined with a 0.05% blood alcohol level produced about the same weaving as a 0.08% blood alcohol level alone, the legal driving limit in most US states. In other words, two "moderate" levels can add up to legally drunk-level impairment. This is perhaps the most serious short-term risk. In a US national alcohol survey, people who used alcohol and cannabis at the same time had about twice the odds of drunk driving, social consequences, and harm to themselves compared with people who only drank.

Greening out — a term for the intense nausea, dizziness, pale skin, and sometimes loss of consciousness that occurs with cannabis overconsumption — is significantly more likely when alcohol is involved. Higher THC levels and alcohol's effect on judgment can push someone past their tolerance threshold even with a dose they would normally handle well. Greening out is rarely dangerous in a medical sense (unlike alcohol poisoning, which can be fatal), but it is an extremely unpleasant experience that can last for hours and may require medical attention if the person is unable to keep fluids down or becomes severely disoriented.

Anxiety and paranoia are also more common with the combination. THC can produce anxiety at higher doses, and alcohol can lower the psychological defenses that normally help people manage that anxiety. The result can be a feedback loop of escalating discomfort — the person feels anxious from the THC, drinks more to calm down, which further amplifies the THC effects, which increases the anxiety. Breaking this cycle usually requires simply stopping consumption of both substances, finding a calm environment, and waiting for the effects to subside.

Long-term health considerations

While occasional combined use of cannabis and alcohol is unlikely to cause lasting health problems for most adults, regular heavy use of both substances together raises several long-term concerns. Research in this area is still developing, but the available evidence suggests that chronic combined use may carry risks beyond what either substance presents individually.

From a liver health perspective, alcohol is well-established as a hepatotoxin — meaning it is directly toxic to liver cells. THC is also metabolized by the liver, but how combined cannabis and alcohol use affects long-term liver health in people is not well understood, and the research so far is mixed.

Mental health is another area of concern. Both alcohol and cannabis can independently affect mood, anxiety, and cognitive function with chronic heavy use. The combination may exacerbate these effects, particularly in individuals who are predisposed to mental health conditions. Some longitudinal studies have found that people who regularly use both substances report higher rates of depression and anxiety than those who use either one alone, though it is difficult to determine whether this reflects a direct causal relationship or a correlation driven by other factors.

Dependence and tolerance are also worth considering. Regular combined use can accelerate the development of tolerance to both substances, meaning you need more of each to achieve the same effects over time. This can lead to escalating consumption patterns that increase both the short-term and long-term risks. Cannabis is generally considered to have a lower dependence potential than alcohol, but psychological dependence on the combination — particularly as a coping mechanism for stress or social anxiety — can develop with regular use.

Harm reduction tips for mixing

If you choose to combine cannabis edibles and alcohol, there are several practical strategies that can significantly reduce your risk of a negative experience. The most important principle is to reduce the dose of both substances. If you normally take 10 mg of THC in an edible, reduce it to 2.5 or 5 mg when you plan to drink. If you normally have three drinks over an evening, limit yourself to one or two when edibles are involved. Both substances amplify each other, so moderating both simultaneously is essential.

Timing and spacing your consumption can make a meaningful difference. Rather than drinking and consuming an edible at the same time, separate them by at least two to three hours. This gives your body time to process one substance before the other begins to take effect, reducing the intensity of the interaction. If you must use both in the same session, many experienced users recommend consuming the edible first and allowing its effects to fully onset before introducing any alcohol, as this gives you a clearer sense of your baseline level of intoxication before adding a second variable.

Stay hydrated and eat food. Both alcohol and cannabis can cause dehydration, and alcohol in particular is more dangerous on an empty stomach. Having a substantial meal before consuming either substance slows absorption and provides a buffer against nausea. Keep water easily accessible throughout the experience, and make a conscious effort to drink it regularly — it is easy to forget about hydration when you are focused on socializing or relaxing.

Have a plan for transportation that does not involve driving. This cannot be emphasized strongly enough. The combined impairment from cannabis and alcohol is far greater than either substance alone, and it persists for many hours — particularly with edibles, whose effects can last four to eight hours. Arrange a designated driver, use ride-sharing services, or plan to stay where you are until you are fully sober. No social event or convenience is worth the risk of driving impaired.

Finally, know your limits and communicate with the people around you. If you start to feel dizzy, nauseous, or uncomfortably intoxicated, stop consuming both substances immediately. Find a comfortable, safe place to sit or lie down, drink water, and tell someone you trust how you are feeling. Most negative experiences from combining cannabis and alcohol resolve on their own with time, rest, and hydration, but having a supportive person nearby can make the experience much less frightening.

When to avoid combining them entirely

There are certain situations and populations where combining cannabis and alcohol should be avoided entirely, regardless of dose or experience level. If you are taking prescription medications — particularly antidepressants, anti-anxiety medications, blood thinners, or any medication that carries a warning about alcohol interaction — adding cannabis to the mix introduces a third variable that your doctor likely has not accounted for. The potential for unpredictable drug interactions increases significantly with each substance you add.

People with a history of substance use disorder should approach the combination with extreme caution, or avoid it altogether. The amplified effects of combining cannabis and alcohol can be particularly appealing to individuals with addictive tendencies, and the combination may accelerate the development of problematic use patterns. If you find that you consistently need both substances to enjoy social situations or relax, that pattern itself may be worth examining, ideally with the support of a healthcare professional.

Individuals with heart conditions should be particularly cautious. Both alcohol and THC can increase heart rate, and the combination can produce a more pronounced cardiovascular response than either substance alone. While this is generally manageable for healthy individuals, it can be dangerous for people with pre-existing heart conditions, arrhythmias, or high blood pressure. If you have any cardiovascular concerns, consult your doctor before combining these substances.

Pregnant or breastfeeding individuals should avoid both substances, and certainly should not combine them. Both alcohol and THC can cross the placental barrier and are present in breast milk. The developing brain is particularly vulnerable to these substances, and no amount of either has been established as safe during pregnancy or breastfeeding. This is one area where the harm reduction advice is unambiguous: abstain from both.

Ultimately, the safest approach is to choose one substance per session rather than combining them. Many people find that cannabis edibles can serve as a satisfying alternative to alcohol in social settings — they provide relaxation and mood enhancement without the calories, hangover, or liver damage associated with drinking. If you do choose to combine them, do so rarely, at low doses, with careful attention to timing, and always with a plan for getting home safely.

Sources

1. Hartman RL, et al. "Controlled Cannabis Vaporizer Administration: Blood and Plasma Cannabinoids with and without Alcohol." Clinical Chemistry, 2015. PMID 26019183.
2. Hartman RL, et al. "Controlled vaporized cannabis, with and without alcohol: subjective effects and oral fluid-blood cannabinoid relationships." Drug Testing and Analysis, 2016. PMID 26257143.
3. Hartman RL, et al. "Cannabis effects on driving lateral control with and without alcohol." Drug and Alcohol Dependence, 2015. PMID 26144593.
4. Subbaraman MS, Kerr WC. "Simultaneous vs. concurrent use of alcohol and cannabis in the National Alcohol Survey." Alcoholism: Clinical and Experimental Research, 2015;39(5):872–879. PMC4399000