A blackout is a temporary condition that prevents short-term experiences from becoming logged into long-term memory.
A person who experiences a blackout may lose time. They may be unconscious for hours, or they may appear conscious and take action, then suddenly “return” to reality as their brains begin to store long-term memories again.
Women appear to be at higher risk of blackouts than men, but anyone with lower body weight, lower body mass index (BMI), lower water-to-fat ratio, slower metabolism, and certain hormonal factors may be at greater risk for blackouts regardless of gender.
Blackouts may be caused by the following:
The most infamous drug associated with blackouts is alcohol.
Drinking too much can put people in a state where they continue to interact and make decisions — including to continue drinking, drive themselves home, engage in risky sexual activities, or perform other dangerous behaviors — but they do not recall these events.
The extent of a blackout can vary from person to person, and it can begin at slightly different levels of blood-alcohol concentration (BAC). Most people begin to black out when their BAC reaches 14 percent.
There are two types of blackouts: complete and partial.
If you completely black out due to intoxication, you will not remember events when your brain was too intoxicated to retain those memories.
A partial blackout means you may have stored some of the memories while you were very intoxicated, but you do not recall them until someone or something reminds you.
Once the brain returns to normal memory productions, the individual will “wake up” from this state and resume normal activity.
Some drugs, including benzodiazepines ranging from Xanax and Klonopin to Rohypnol, can lead to blackouts.
The mechanism in the brain that triggers a blackout may be similar to alcohol since benzodiazepines and alcohol both work on the gamma-Aminobutyric acid (GABA) receptors. Both alcohol and benzodiazepines, such as Xanax, increase the bioavailability of the GABA neurotransmitter by binding to the GABA receptor sites, so more natural GABA is present to slow down communication between neurons. Slowed communication, at high levels, can mean that memories simply do not make it from short-term memory to long-term storage.
People who binge drink regularly are at greater risk of having blackouts, so people who take large doses of Xanax routinely to get high or feel relaxed may also be at greater risk of blacking out. However, with a prescription drug like Xanax, the experience of blacking out is not colloquially called a blackout. Instead, it is called anterograde amnesia.
Simply put, anterograde amnesia is a condition affecting the brain when the organ cannot retain new information very well or at all. It is a subset of amnesia in general, which involves memory loss.
A 2010 study published in Neurobiology found that seven out of 10 people with anterograde amnesia could learn enough to temporarily retain new information; however, with repetition, this information did not move into long-term memory due to “retroactive interference.” This may occur when new information interferes with the storage of old information, like when learning a new number changes one you just learned; however, it can also be caused by chemical interference, such as being intoxicated with a sedative drug like Xanax.
While alcohol broadly impacts the GABA receptors in the brain, benzodiazepines like Xanax are more targeted. They impact GABA-A receptors in particular. There are two subtypes of GABA-A receptors:
Most studies involving the impact of benzodiazepines on GABA-A receptors have focused on BZ-2. Benzodiazepines with more hypnotic properties, which impact memory and allow the brain to slow enough to fall asleep, are not as frequently prescribed for anxiety. Xanax is believed to have fewer hypnotic properties compared to anxiolytic, or anxiety-reducing, properties, but this may not be true.
Memory is typically defined by:
Previous medical studies have shown that benzodiazepines, including anti-anxiety ones like Xanax, have a greater impact on episodic memory, leading to long-term issues. However, more recent surveys have found that all benzodiazepines have a broader impact on retaining information of all kinds than previously believed. This may mean that acute intoxication from taking too much Xanax can lead to blackouts.
Some of the broader memory problems associated with taking Xanax or other benzodiazepine is that a mild level of stimulation, including feeling anxious, can improve cognitive performance. Without enough neuronal firing, the brain simply does not keep information in short-term storage long enough to move it to long-term storage.
There is also some association between increasing tolerance for benzodiazepines, leading one to take more of the drug, which increases the experience of anterograde amnesia. In one study, anecdotal reports note that those surveyed remembered what they did when they were on large doses of a benzodiazepine, but their judgment and inhibitions were lowered, so they got involved in risky behaviors or embarrassing situations and later felt ashamed after the drug’s effects wore off.
The survey continued that, unlike alcohol, the exact level and effect that a short-acting benzodiazepine would have on memory were subjective and unpredictable. Participants reported episodes of blacking out that lasted for a few seconds, minutes, hours, or even days. It was more predictable that survey participants had little to no recollection of the day after they initiated taking the drug.
Abusing Xanax can be as risky for the brain as abusing alcohol, so it is important to get evidence-based treatment.
Withdrawal symptoms associated with Xanax can be dangerous, so working with medical professionals to taper or ease these symptoms is important. Then, entering a rehabilitation program focused on therapy will help to change behaviors around drugs and alcohol.
(December 22, 2016) Understanding Why Blackouts Happen. Healthline. from https://www.healthline.com/health/what-causes-blackouts.
The Forgotten Science of Blackouts. MEL Magazine. from https://melmagazine.com/en-us/story/the-forgotten-science-of-blackouts.
(March 21, 2018). This is Your Body on Xanax. Vice. from https://www.vice.com/en_au/article/9kzx8z/this-is-your-body-on-xanax.
(September 29, 2017). Anterograde Amnesia. Healthline. from https://www.healthline.com/health/amnesia/anterograde-amnesia.
(November 16, 2006). Anterograde and Retrograde Effects of Benzodiazepines on Memory. The Scientific World Journal. from http://neurologiauruguay.org/home/images/publicacion/benzodiazepines%20and%20memory.pdf.
(September 2016). High-Dose Benzodiazepine Users’ Perceptions and Experiences of Anterograde Amnesia. The Journal of the American Academy of Psychiatry and the Law. from http://jaapl.org/content/44/3/328.