If you’ve ever woken up from a night of drinking, realizing you have very little memory of the events that took place, you know how scary a blackout can be. But even more worrisome is what goes on in your body and brain during that period.
According to George Koob, the director of the National Institute on Alcohol Abuse and Alcoholism, blackouts are “a gap in the tape” of your memory, so to speak. “At roughly twice the legal limit, a blood alcohol content of .16, you become vulnerable for a blackout ― although this varies,” Koob said. “In a blackout, alcohol shuts down the ability of the brain to consolidate memories.”
Scary, right? Experts describe exactly how alcohol works in your system when you’re drinking heavily ― and how to tell when you’re getting to the point where you’re at risk of blacking out:
The primary ingredient driving your alcohol-related symptoms is ethanol, a compound found in the alcoholic beverages you drink. As you drink one to four drinks or more in a short span of time, the effects of the substance become more pronounced. This is especially true if you have not eaten much.
“When the stomach is empty, peak blood ethanol levels are reached between 30 and 90 minutes after ingestion.” In other words, as you drink, your blood ethanol level, which is what helps determine what most people know as their blood alcohol concentration, or BAC, will inch higher and higher for around an hour. This also means you may not realize how drunk you’re getting until you’ve already tipped back one too many.
A couple of hours into drinking, the ethanol “can freely diffuse across the blood-brain barrier,” Kaplan said. The alcohol can then target receptors in the brain’s hippocampus (the part of the mind that controls functions like emotions and recollection), including one receptor known as the gamma-aminobutyric acid, or GABA, receptor. When GABA receptors are affected by alcohol, the transmission of signals in the brain stops ― including signals that will solidify memory ― which then results in a blackout, Koob said.
Additionally, alcohol inhibits a neurotransmitter in the brain called glutamate, which results in you feeling calmer. Drinking also “releases other inhibitors, such as dopamine and serotonin,” Kaplan said, which are chemicals that prompt those happy emotions.
Koob added that as the alcohol in your blood is increasing, you may also be compelled to act out of character, thanks to the chemical changes in your brain.
“In the blackout zone, you could be dancing on a table in front of your boss, but the next day you’re not going to remember a thing,” he explained. But, and this is important to know, he said a blackout is “not permanent damage to the brain, but rather a gap in time” where the brain is not producing any memory.
Subscribe to HuffPost’s wellness email
How To Recognize The Blackout Point
Consuming alcohol to a degree where you’re at risk of blacking out is problematic ― and you may notice someone who is getting to an unsafe point (or maybe it’s been you in the past). As alcohol is cascading through the brain, the person drinking may not seem like themselves, but Kaplan said specific symptoms will likely vary.
“It is not always obvious when someone is close to blackout,” he said. “There may even be delayed effects between symptoms of ‘coherence’ and what they do and don’t remember. And remember, different parts of the brain may be reacting differently, causing these different effects.”
“Slurred speech is also common, and people are sensitive to that; it’s why police use it as a test,” Koob added. “Also, same with motor coordination. They might be bumping into things. It’s hard to walk in a straight line when you’re that intoxicated.”
Koob said there’s usually a tipping point where it becomes apparent in a person’s behavior, as well.
“One marker I use is dramatic and rapid swings in emotionality,” Koob said. “One moment, your friend might be praising you and telling you how much they care. The next, they turn, and it’s the complete opposite emotion, like anger directed at you.”
In this case, short-term risks range from “electrolytes and system dysfunction to bodily harm from trauma after a fall,” Kaplan said. “We all have heard of stories of intoxicated people falling down the stairs, or having head and brain trauma, possibly death.” If a person’s BAC inches toward 0.3, they can also enter a coma or it can be lethal.
Koob stressed that the key to drinking is moderation. If you’re interested in finding out how alcohol affects you personally based on your height, weight and number of drinks you consume, there are calculators that can estimate these factors and give you more information. But, bottom line, drinking to the point of blackout ― especially repeatedly ― is always an issue for your long-term health.
“You set the stage for cancer, heart problems, liver problems, even permanent brain deficits,” Koob said. “Something everyone has to learn if they want to drink is their own limits.”