Rates of heavy alcohol use and alcohol use disorder peak in young adulthood around ages 18-25 years [1]. In 2023, an estimated 27% of young adults reported binge drinking (5+ drinks in a row) in the past 2 weeks, and 9% reported past 2-week extreme binge drinking or high-intensity drinking (10+ drinks in a row) [2]. An estimated 5.1 million young adults met criteria for a past-year alcohol use disorder in 2023 [1]. Even more common are acute negative outcomes of heavy drinking (eg, social-interpersonal consequences and adverse physical effects) [3]. A key negative consequence of heavy alcohol use is blackout drinking, or alcohol-induced memory loss during a drinking episode. Blackouts are common among young adults who consume alcohol, with approximately 50% reporting a lifetime history of a blackout [4]. Blackout drinking is particularly concerning given its associations with further harms from drinking, including physical injury, sexual assault, and overdose [5].

Controlled lab experiments have established the effects of alcohol use on postintoxication cognition in young adults [6,7]. Alcohol-related deficits have been identified in working memory [8], attention [9,10], psychomotor functioning [11,12], processing [13], and executive functioning [14]. Further, recent experimental evidence identified decreased volume in the posterior and central corpus callosum several days after one’s 21st birthday (ie, a single heavy drinking event), even after adjusting for lifetime alcohol and cannabis use, and these effects were more pronounced among individuals who experienced a blackout during the event [15]. While this evidence suggests a link between heavy drinking and structural brain damage postintoxication, it is unclear whether heavy alcohol use also impacts daily cognitive functioning, such as working memory and attention, among young adults. Given that changes to the corpus callosum impact communication between hemispheres, heavy drinking potentially reduces functional adaptation across regions, particularly under cognitive load [16]. Cognitive and brain reserve capacities describe the potential for individuals to compensate for changes in brain structure with learned strategies to avoid experiencing declines in cognitive functioning [17,18]. Hence, this initial evidence supports early theorizing on the role of substance use in altering cognitive and brain reserve capacity [19], suggesting that alcohol and other substance use may disrupt the development of this compensatory mechanism in young adults, ultimately leading to greater functional impairment.

As noted in Pearlson [20], a critical area of further exploration is whether young adults actually experience functional cognitive consequences or disruptions in general everyday cognitive functioning as a result of heavy drinking. Particularly for young adults whose brain can typically accommodate structural changes [21,22], structural brain alterations may be reversed in the long term due to the plasticity of their brain [22,23]. A more salient indicator may be younger individuals’ experiences of changes in everyday cognitive functioning [24]. Young adults who notice deficits in daily cognitive functioning may reduce engagement in cognitively stimulating activities (eg, social activities), establishing lifelong patterns of lower cognitive functioning.

Ecological momentary assessment (EMA), or collecting self-reported and behavioral data in real time and context via mobile devices, is ideal for studying functional changes in cognition. Disruptions in cognitive functioning can be small and are best captured via granular, sensitive measures in natural environments [25]. Functional changes can be observed in both objective measures (eg, executive functioning and memory) and subjective measures (eg, attentional lapses and difficulties concentrating). Beyond cognitive assessment, EMA has also been widely used for assessing alcohol use and its consequences among young adults [26,27]. Reporting on alcohol use in real time or the next morning can maximize recall of the amount of alcohol consumed [28]. Accurately identifying the number of drinks consumed in a drinking episode has important implications for identifying high-intensity drinking (8+ or 10+ drinks consumed in a day for female or male individuals, respectively) [29], which is associated with heightened risks for acute same- or next-day harms (eg, passing out or losing control) [30].

Analytically, EMA is ideal for examining the dynamic associations between alcohol use and cognition in daily life and for identifying contextual and person-level risk factors that may moderate such associations. EMA can be used to tease apart between- and within-person effects and thus isolate day-level effects of alcohol use on cognitive functioning on days with varying alcohol use intensity or experiences of blackout drinking. To date, very limited EMA or diary work has examined the role of alcohol use on cognitive functioning. In one study, higher intensity drinking was associated with difficulties in next-day self-reported attention and concentration [31], but performance-based measures of cognitive functioning were not assessed. Another EMA study examined the specific role of substance use on working memory across 7 days in a sample of young adults, finding that working memory was lower when using alcohol relative to not [32], but participants did not self-report experiences with their cognition. Among a sample of middle-aged and older adults who completed 8 days of surveys, participants self-reported their experiences with memory lapses and were more likely to have memory lapses if they drank more alcohol than the average amount they consumed [33].

As noted in prior EMA work, there is likely an acute impact of alcohol use on cognitive functioning that warrants further investigation, though several gaps in our understanding remain. First, with a more comprehensive assessment of cognitive functioning, we can determine whether the impacts of different levels of alcohol use are specific to a particular type of cognitive process (eg, working memory), global across cognitive processes (eg, fluid intelligence), or particular to an individual’s perceptions of their ability to recruit those processes to complete daily tasks (eg, self-reported cognitive functioning). Second, through multiple assessments throughout the day, we can explore the duration of the effect of alcohol use intensity on next-day cognitive functioning (eg, do effects occur only upon waking or persist throughout the day?). Third, given the unique risks of blacking out [5,34] and the more profound structural impairments linked to blackout episodes relative to heavy drinking without blacking out [15], research exploring blackout drinking and cognitive functioning is warranted.

Following informed consent, interested participants completed a brief web-based screener to determine eligibility. Eligible participants were automatically routed to complete a web-based baseline survey and cognitive assessments, which took approximately 30 minutes to complete. Participants completed a demographics survey; self-reported cognitive functioning items; performance-based cognitive assessments of episodic memory, executive functioning, and working memory; and self-reported typical alcohol use behavior (see Table 1 for the assessment battery). These measures represent key cognitive processes likely to impact daily functioning [43,44]. For episodic memory, participants completed a paired associates task: here, a list of 10-word pairs is presented, then participants are shown the first word of each pair and asked to recall the second. For executive functioning, participants completed a task-switching exercise categorizing objects by color (blue or green) or shape (square or rectangle) as quickly as possible based on a cue. For working memory, participants viewed 4 boxes that changed color in a random sequence and had to indicate when the same box changed colors twice in a row. Screening and baseline survey data were collected and managed with Research Electronic Data Capture (REDCap).

Follow-up surveys for the EMA portion of the study were collected online across 21 consecutive days (see Table 1 for a list of measures). Participants were sent email and text message prompts with the associated survey link daily at 11 AM, 1 PM, 3 PM, and 5 PM. The first prompt that participants completed each day included survey items about the prior day (“prompt 1”), including previous-day alcohol and other substance use, blackout drinking experiences, sleep, hangover symptoms, current mood, and cognitive functioning, plus objective (performance-based) assessments of cognition. At each subsequent assessment that day, participants reported on current substance use and mood and cognitive functioning was evaluated via both self-reported and objective cognitive measures. At the time of each prompt, participants were advised that they had 60 minutes to complete the survey questions and brief objective cognitive tasks. Average completion time per survey was approximately 3 (SD 6.12) minutes, and 90% of surveys were completed in less than 5 minutes. The EMA protocol was collected via Qualtrics. All objective cognitive assessments were collected and managed in the Gorilla Experiment Builder [64].

Participants received up to $193 for full study participation. Specifically, participants received $10 for completing the baseline survey, $2 per prompt completed, and $5 per week bonus for completing at least 20 out of 28 surveys each week.

We used simulations of planned multilevel models to account for dependencies in the data (SAS 9.4). For our primary objective (day- or moment-level associations between alcohol use and cognitive functioning outcomes), with n=300 and up to 84 surveys (21 days × 4 surveys per day), we have >80% power to detect relations between alcohol use and cognitive functioning accounting for 1% of variance. As some participants will not complete all surveys, we examined power for 80% and 50% compliance. These additional simulations resulted in power of >80% to detect the same relationship, indicating sufficient power in the presence of missing data. For secondary objectives, we are interested in differences due to day- and person-level moderators. To be conservative, we examined only scenarios with incomplete data (50% and 80%). Assuming these conditions, we can detect differences across moderators accounting for 1.7% and 1.6% of the variance, respectively.

The institutional review board at the Pennsylvania State University approved all study procedures (#STUDY00022639). Participants provided informed consent before enrolling in the study. Study data are deidentified.

Identifying the acute associations between alcohol use and blackout drinking behavior on next-day cognitive functioning, as well as the day- and person-level characteristics that moderate these associations, will provide critical information about the role of alcohol use on everyday cognitive functioning and highlight subgroups most in need of monitoring and early intervention. Findings will guide prevention and intervention programming in several key ways. Identifying whether and at what levels alcohol use impacts cognitive functioning can be used as an intervention tool: momentary interventions could incorporate timely feedback on young adults’ self-reported prior-day alcohol use and objective, current cognitive functioning. Day-level moderators, such as hangover symptoms, mood, sleep, and prior-day cannabis and other substance use [35,37-40,42] may affect associations, and momentary intervention content can be tailored to participants’ own risk factors and delivered in moments of greatest risk. Similarly, intervention content on typical drinking patterns and personal risk for cognitive concerns may be incorporated in existing brief motivational interventions tailored to young adults. Person-level variables that independently and synergistically impact alcohol use and cognition (eg, sex, alcohol use severity, and general cognitive functioning) [36,41] will identify higher-risk groups in need of targeted interventions.

Specific to examining blackout drinking, there have been several recent calls to include blackout-specific content in preventive interventions [4], as personalized information on typical drinking patterns, including blackout drinking, could maximize intervention impact. For some young adults, blackout drinking is associated with later drinking-related consequences [65]; thus, incorporating objective, deleterious outcomes of blackout drinking may help detect and intervene on problematic alcohol use patterns earlier. Given that brief alcohol interventions are more effective among individuals who have experienced a blackout [66], and interventions incorporating blackouts are estimated to save approximately $500,000 per year in emergency department visits [67], investigating within-person risks of blackouts and other problematic alcohol use behaviors (eg, high-intensity drinking) within this age group appears promising and impactful.

It should be noted that future findings from this exploratory and developmental study should be interpreted with several caveats. First, generalizability to young adults who are not attending college or are attending a 2-year program may be limited as the data were from individuals aged 18 to 25 years currently attending a 4-year institution. Second, participants predominately identified as non-Hispanic White and female sex assigned at birth, which may limit the generalizability of findings to minoritized racial-ethnic groups and to men. Finally, although some of our cognitive assessments are objective performance-based, the majority of our data are based on participants’ self-reports and may be impacted by social desirability or recall bias.

Overall, the findings will provide critical insight on the impact of alcohol use on daily cognitive functioning and will highlight subgroups and days at highest risk as targets for intervention. Results will position us to expand upon this work to (1) study young adults for a longer duration to determine whether cognitive functioning concerns accumulate over time and predict longer-term alcohol-related and cognitive problems; (2) study mechanisms underlying the link between alcohol use and cognitive functioning, including concurrent structural and functional brain changes; and (3) examine the role of day- (eg, cannabis) and person-level (eg, use severity) on the alcohol–cognitive functioning link.