Excess alcohol and substance use can cause temporary and permanent memory loss

What are blackouts and brownouts?

Blackouts involve complete memory loss caused by your brain’s inability to record new memories for a period of time due to the effects of excessive alcohol, substance misuse or some other condition.

But sometimes, auditory or visual cues can help a person piece together memories of what happened during a blackout. These cues could come in the form of texts, pictures or conversations with people who were present while you were blacked out. The medical term for blackouts is called transient loss of consciousness (TLOC).

The difference between a brownout and a blackout is that brownouts involve partial memory loss. With a brownout, you may be able to remember certain details from the period of time you were affected, but other portions of time can’t be recalled.

“The hippocampus is a part of your brain that takes our experiences and the awareness of all our senses and processes those into memories,” explains Dr. Streem. “It’s sensitive, and it’s the same part of the brain that deteriorates in people with Alzheimer’s disease.”

Excessive alcohol use isn’t the only thing that can cause blackouts or brownouts. Substance misuse on its own or with alcohol can increase your likelihood of experiencing a blackout. Hypnotics or sedatives and benzodiazepines like flunitrazepam (also known as Rohypnol or roofies) can also lead to blackouts or brownouts.

There are other medical conditions that cause blackouts or brownouts, too, including:

• Chronic traumatic encephalopathy (CTE).
• Traumatic brain injury.
• Stroke.
• Psychogenic nonepileptic seizures (PNES).
• Post-traumatic stress disorder (PTSD).

“Anything that causes damage to the brain, whether temporary or permanent, can cause memory loss if the damage is in the right spot,” states Dr. Streem.

Is a blackout the same as passing out?

Blackouts are not the same as passing out. When you pass out or faint, you experience a temporary loss of consciousness.

“When you’re passed out, you’re not awake. A blackout happens to someone who’s still conscious but they’re not coding any new memories,” explains Dr. Streem. “A person who has a blackout is still awake and they have some ability to think, but other parts of their brain may not be working well enough. Often, this is because of intoxication.”

Understanding these definitions and the difference between blackouts and passing out is incredibly important, as it may be difficult for other people to recognize someone is having a blackout because of their seemingly aware state.

How much alcohol can cause a blackout?

How much alcohol or substance use is needed to cause a blackout varies based on a person’s height, weight, sensitivity and assigned sex at birth.

“We know females absorb more alcohol in their bloodstream than males,” says Dr. Streem. “But for most people, it’s going to involve more than the legal blood alcohol limit. In almost all states in the U.S., the blood alcohol limit for driving is .08. Blackouts usually appear at blood alcohol levels that are twice the legal limit or higher.”

Studies have shown that young adults under the age of 25 are particularly vulnerable to experiencing blackouts. Additionally, blackouts may occur at far lower thresholds among younger populations. That’s largely because the parts of your brain responsible for decision-making aren’t fully matured until around age 25. Despite this, intentional binge drinking has been a common practice among young adults.

Regardless of age, recent studies show more frequent blackout experiences are related to an increase in memory lapse and cognitive difficulties even after alcohol misuse is corrected. This means that even after a blackout occurs, you can continue to experience memory loss and other difficulties recalling memories.

Blackout effects on your body

If you’re experiencing a blackout or brownout, you’re at higher risk for falling, injury and unwanted or unsafe sexual experiences. A person who is blacked out may also throw up while sleeping, which could lead to an increased risk of choking or suffocating.

It can be hard to determine when you’re going to have a blackout or brownout. But some signs it may be happening to you in the moment include:

• Difficulty standing.
• Nausea.
• Lightheadedness.
• Loss of vision or shrinking of your field of view.

Other signs of substance-related blackouts, specifically blackouts caused by sedatives, hypnotics or benzodiazepines, include:

• Loss of bowel or bladder control.
• Difficulty breathing.
• Feeling drunk when you haven’t consumed alcohol or consumed less than your usual amount.
• Sudden body temperature changes.
• Sudden increase in dizziness, disorientation, loss of vision or difficulty speaking.

“Hypnotic drugs are prone to cause this kind of impairment and memory loss,” states Dr. Streem. “Sadly, people sometimes use them to take advantage of other people.”

Strategies for managing blackouts

A blackout ends when your body has absorbed the alcohol you consumed and your brain is able to make memories again. Sleep often helps this process along.

Alcohol is dehydrating by nature, so making sure you’re drinking plenty of water and staying hydrated is important. Being aware of potential signs of intoxication can also be helpful in understanding your limitations.

But what if you end up having a blackout anyway?

“The experience of a blackout can sometimes be an opportunity to learn about our bodies and our brains, and what we can and can’t handle,” says Dr. Streem. “But the most important thing to do when you have a blackout is to try and piece together as best we can what happened and whether we were injured. It also might be necessary to try to assess whether you’ve been taken advantage of in some way.”

If you think you’ve been injured, sexually or physically assaulted, it’s important that you get medical attention immediately and talk to the police about everything you can remember.

Other measures you can take to reduce the likelihood of blackouts and brownouts and increase your own safety include:

• Drinking with people you trust.
• Pairing up with a close friend or group of friends and leaving together.
• Not drinking on an empty stomach.
• Not taking drinks from other people.
• Opening containers yourself or watching your drink being poured.
• Taking your drink with you when leaving a room.
• Not drinking anything that tastes or smells odd.
• Asking for help when you start to feel drunk or intoxicated.

“There’s no way to prevent a blackout or brownout from happening other than to stop consuming so much alcohol or other substances that cause them,” says Dr. Streem. “Beyond that, safety and general physical care can be very helpful in making sure this doesn’t happen to you.”