This preclinical study in C57BL/6J mice tested how adolescent social context influences ethanol consumption. Major observations were that social isolation during adolescence increased ethanol intake in a binge-like Drinking in the Dark (DID) model in both sexes, whereas group housing with concurrent ethanol access reduced consumption. Neighbor-cage housing — allowing proximity but not full shared housing — produced only small reductions in intake compared with full isolation. Increasing the number of ethanol bottles per cage raised total ethanol volume consumed but did not alter the relative difference between group- and single-housed animals. A history of adolescent binge drinking increased adult intake and preference on select days, but this carryover effect was limited to mice that had been group housed during adolescence.
Adolescence is a developmental window characterized by heightened sensation seeking, impulsivity, and evolving social behavior. In humans adolescence spans roughly ages 12–20; in rodents it approximates postnatal day (P) 21–60. Alcohol is the most commonly misused intoxicant among adolescents: the source reports 7.1 million underage youth (ages 12–20) reported drinking in the past month and 4.3 million reporting binge drinking (four or more drinks for women, five or more for men) in a single occasion. Alcohol exposure during adolescence can disrupt synaptic pruning and myelination and is associated with accelerated grey matter reductions in frontal, cingulate, and subcortical regions. In rodents, adolescents show greater sensitivity to alcohol’s rewarding effects and reduced sensitivity to aversive effects compared with adults, which may contribute to higher voluntary ethanol consumption during adolescence.
Social interactions are crucial for normal adolescent development. Prior rodent studies typically report that post-weaning social isolation increases adolescent ethanol consumption, though results have been mixed and sometimes sex dependent. Few studies have simultaneously manipulated adolescent social context and ethanol access during adolescence to determine combined effects on both adolescent and later adult drinking; this study addressed that gap.
Male and female C57BL/6J mice arrived at postnatal day 21–22 and were initially housed 4 per same-sex cage for about one week. Mice were then randomly assigned to one of several housing conditions maintained through the experimental intervals: single housing (one mouse per standard shoebox cage), group housing (multiple same-sex mice sharing a cage), or neighbor-housed complexes (four standard cages connected by ports fitted with wire mesh that allow sensory contact without full cohabitation). Bedding and husbandry followed standard facility conditions under a 12-hour light/dark cycle. Food and water were available ad libitum except during four-hour DID sessions when diluted ethanol was the only liquid offered.
Ethanol intake was assessed using two commonly used paradigms. The intermittent two-bottle choice allowed access to ethanol alongside water across selected sessions. The Drinking in the Dark (DID) model provided a limited four-hour access period to diluted ethanol as the only available fluid, modeling binge-like consumption. The experiments varied social context at the time of drinking (single, neighbor, or group housed) and manipulated the number of ethanol bottles per cage to determine effects on absolute and relative consumption.
When ethanol access occurred in the presence of a conspecific within the same cage (group housing), mice consumed significantly less ethanol compared with single-housed (isolated) mice, indicating that the presence of cage-mates reduced the motivation to drink. Single housing increased adolescent ethanol intake in the DID model for both sexes. Neighbor housing — cages in proximity with mesh ports permitting interaction without shared cage space — resulted in only modest decreases in ethanol intake compared with full isolation, and overall ethanol intake from adolescence into early adulthood was largely unaffected when comparing neighbor housing to single housing in some measures. Manipulating the number of ethanol bottles per cage increased absolute ethanol volume consumed but did not change the relative pattern: group-housed mice still drank less than isolated mice.
The investigators examined whether adolescent drinking and social context influenced later adult ethanol consumption. They report that adolescent binge drinking increased adult intake and preference on selected days, but this effect occurred only in mice that had been group housed and drank socially during adolescence. The study therefore found that the lasting impact of adolescent binge exposure on adult drinking was context dependent.
The results indicate that social context during adolescence modulates ethanol consumption in mice: isolation tends to increase binge-like drinking, while drinking in the presence of conspecifics reduces intake. The findings suggest that social facilitation or suppression of drinking is an important determinant of adolescent ethanol intake in rodent models and that proximity alone (neighbor housing) is not equivalent to shared social housing. The observation that adolescent binge exposure increased adult intake only in group-housed mice highlights complex interactions between social environment and the long-term consequences of adolescent alcohol use.
These preclinical observations align with human data associating solitary drinking and perceived social isolation with elevated risk for subsequent alcohol use problems. The study supports the importance of considering social context when modeling adolescent alcohol use and in developing interventions aimed at preventing problematic adolescent drinking.
The authors state that all relevant data are within the paper and additional files are available at OSF (doi: 10.17605/OSF.IO/9NB37). Funding was provided by the National Institute on Alcohol Abuse and Alcoholism (NIH grants R01AA026347 and P50AA022537). The authors declared no competing interests.