Study tests whether a simple memory quiz while drinking can spot alcohol blackouts in real time

Hidden harms

While alcohol-induced blackouts used to be viewed by some as a marker of dependence on alcohol, they can actually happen to almost anyone who drinks either too much or too quickly or both, said Jennifer E. Merrill, a professor of behavioral and social sciences at the Brown University School of Public Health and a co-author of the study published in the journal Addiction.

“When a person is in the midst of a blackout, they are not aware of that, and typically, it is difficult for anyone around them to know that they aren't forming long-term memories,” Merrill said. “If we were able to identify that someone was blacked out — or imminently at risk for blacking out — in real-time, others could intervene or intervention content could be sent digitally, to disrupt further consumption placing them at even greater risk.”

The study was led by former Center for Alcohol and Addiction Studies postdoctoral researcher Mary Beth Miller, who is now at the University of Missouri-Columbia, and included Merrill and colleagues from several institutions. The researchers want to better understand blackouts and to detect them because they are a common but often hidden form of alcohol-related harm.

Testing memory

The theory behind the new study was simple. If alcohol is disrupting the brain's ability to form new memories, then people experiencing a blackout should have difficulty remembering something they saw just minutes earlier.

To test that idea, researchers recruited 63 people ages 18 to 30 who reported frequent alcohol-related memory loss. Over a 30-day period, participants completed memory tests on a smartphone while drinking. They were shown an image on their phone and, 15 minutes later, asked to recall what they had seen.

The next day, participants reported whether they had experienced alcohol-related memory loss, ranging from fuzzy or incomplete memories to a complete inability to remember what happened while drinking.

Findings

One of the study's key findings was that the approach was feasible in real-world settings. Participants completed about 85% of the memory tests they were prompted to take, with similar participation rates on blackout and non-blackout nights.

The researchers also found that passing the test was more informative than failing it. Most of the time when people failed a memory test, they did not report a blackout. In fact, only about 39% of failed recall tests were followed by a reported blackout.

The test was especially effective at ruling out the most severe forms of alcohol-related memory loss. Among participants who passed all recall tests, 99% did not later report a complete blackout.

That distinction matters, they said, because a failed memory test could result from distraction, inattention or other factors. Successfully recalling information suggests the brain is still encoding new memories despite alcohol consumption.

Of all the blackouts reported by participants during the study, the memory test showed moderate ability to flag drinking episodes that would later be associated with memory loss. About 60% of blackout episodes were associated with at least one failed recall test.

The test also correctly identified most drinking occasions that did not result in memory loss and performed especially well when it came to the most severe blackouts. The findings suggest the approach may be more useful for ruling out major memory impairment than for definitively identifying it.

The findings come with an important caveat. Researchers had to rely on participants' reports of whether they experienced a blackout the following day. As a result, some blackout episodes may have been missed or incorrectly reported. It’s part of why blackouts are so tricky to study, Merrill said. “We are asking people to remember what they forgot.” 

The new study is only a first step. Merrill said the research team next hopes to improve the test's ability to predict blackouts and explore how memory performance changes alongside levels of intoxication over the course of a night, a line of research that could have implications for a far broader group of people who drink than many people realize.

“If we can continue to refine methods for identifying blackouts in real-time, when they occur, opportunities for both research and interventions could really open up,” she said.