Nicotine is the only drug that eclipses alcohol and marijuana as the most commonly used drugs in the U.S., according to the National Institute on Drug Abuse. So, it makes sense that the latter two are also the most common drugs to be used together. Although most people probably have a preference of which drug they prefer, you most likely wouldn’t have to go very far to get a firsthand account of what it’s like to be high on alcohol and marijuana at the same time. What many don’t understand is the biology behind the side effects that follow using these drugs concurrently.

Why Cross Fade?

Using alcohol and marijuana at the same time is often referred to as "cross fading." Some people will mix the two because they enjoy the unique high it gives them. For others, they are already so intoxicated with alcohol that they are no longer making rational decisions. To them, taking a toke of a joint seems like a good idea at the time, although some may regret it later. Although a college student may not be able to tell you what the main subject on their senior thesis is, they most probably can tell you that smoking grass before beer, you’re in the clear, while beer before grass, well... isn’t as advisable. Is there any science behind this coming of age mantra passed down through generations? Turns out, there actually is.

Greening Out

Greening out is a term used to describe a situation where a person may feel sick after smoking marijuana. The individuals may go pale and sweaty, feel dizzy with “the spins,” nauseous, and may even start vomiting. This is most commonly followed by the immediate desire to lie down. Greening out is not a very common side effect of smoking marijuana, but it is much more likely to occur if a person has been drinking alcohol before they start smoking. However, when an individual smokes marijuana before they drink alcohol, the effect is not the same.

Overdoing It

Using alcohol and marijuana in combination is more likely to make the individual overuse both substances. It is common for an individual to experience the effects of marijuana more severely when they have already have alcohol in their system. Although “greening out” is not life-threatening, the effect of overdoing alcohol — alcohol poisoning — surely can kill you. Using both substances can make the individual drink beyond their tolerance and therefore be more likely to experience alcohol poisoning. According to Northeastern University, marijuana has an antiemetic effect, meaning that it makes it more difficult for the body to vomit. Normally this side effect is non-consequential, and it can even be beneficial in cancer patients who use medical marijuana because they have trouble keeping food down. However, in the case of alcohol poisoning, vomiting is the body’s way of expelling the excess alcohol. If a person is unable to properly vomit, they are more likely to choke on their vomit or succumb to the effects of alcohol poisoning.

Intensified Highs are Not Always a Good Thing

Alcohol is a depressant and slows down the central nervous system. Marijuana also slows the body down. Using them concurrently will magnify the effects of both, but how is highly unpredictable. Having alcohol in your blood can also potentially cause your body to absorb the THC faster. Based on information from Australia's National Cannabis Prevention and Information Centre (NCPIC), in vulnerable people, the combination can produce psychotic symptoms such as panic, anxiety, or paranoia. Alcohol is known to have a very unpleasant side effect of making you "black out." New studies are just beginning to show the detrimental effects of marijuana use on memory. It can disrupt the activity in the hippocampus, the area of the brain that controls memory. When used together, it can seriously fog an individual’s mind, making them more susceptible to dangerous situations such as being less able to look after their belongings and more likely to be unable to negotiate safe sex.

Unknown Effects

The separate effects of alcohol and marijuana use on the body are pretty much fully documented. Not as much is known about the combined effects. According to data from Northeastern University, these can vary from person to person. Some people can get sick and pass out, and others will say they had the time of their life and can’t wait to do it again next weekend. When used together, the likelihood of having a bad reaction increases significantly, according to the NCPIC. Mixing alcohol with any substance, legal or not, can intensify the side effects and create negative interactions.