The impact of social isolation on the development of alcohol use and alcohol addiction-related processes in animals: a systematic review.

Social isolation significantly shapes drinking behaviour, acting as both a risk and protective factor. Animal models provide controlled causal examination of how social isolation shapes alcohol-related behaviours and underlying mechanisms. This systematic review examined how social isolation shapes the subsequent development of alcohol consumption and addiction-related processes in mammals from an alcohol-naïve baseline, evaluating the moderating roles of sex and age of isolation onset. Systematic searches of Embase, PubMed, and PsycInfo up to April 2026 identified 66 studies comparing alcohol consumption or addiction-related processes between isolated and socially housed mammals. Social isolation was associated with higher alcohol consumption and enhanced motivation across behavioural paradigms, though these effects were highly dependent on age of isolation onset and other moderating factors. Isolation at weaning age produced stronger effects than isolation in adulthood. Evidence for sex as a moderator remained inconsistent. Across fourteen studies of neurobiological outcomes, the clearest pattern was elevated dopaminergic and noradrenergic signalling in isolated animals following alcohol exposure, particularly at higher doses, while GABAergic, opioidergic, and serotonergic systems showed more region- and subunit-specific effects. In conclusion, social isolation shapes alcohol consumption in a manner that is highly dependent on moderating factors, alongside corresponding alterations in reward processing and stress reactivity that may underlie these behavioural patterns. Age of isolation onset emerged as a consistent moderator. These findings provide a preliminary mechanistic explanation of how social isolation shapes the development of alcohol use and alcohol use disorder, while also highlighting how methodological decisions in preclinical addiction research shape outcomes.