A study found that loneliness or social isolation can change how brain circuits work and may influence alcohol intake. In socially isolated male mice, a specific brain circuit became overactive, and this change led to an actual increase in alcohol consumption.
A joint team from Northwestern University and the Salk Institute for Biological Studies reported on the 25th in the international journal "Nature Neuroscience" that they identified a specific brain circuit involved in how social isolation leads to increased alcohol intake in male mice.
Lately, loneliness and social isolation have drawn attention as major public health issues. Previous studies have reported that social isolation is linked not only to depression and anxiety but also to the risk of substance misuse, including alcohol. But it has not been clearly revealed what changes an isolated environment causes in the brain and how those changes lead to drinking behavior.
To investigate this, the researchers ran experiments with adult male and female mice. At first, several mice lived together, and then some were housed one per cage to create an environment similar to social isolation. The others continued living in groups as a comparison group. The mice were then allowed for about two weeks to choose freely for one hour a day between water and a 15% alcohol solution.
As a result, male mice that lived alone gradually increased their alcohol intake over time. In contrast, socially isolated female mice actually decreased their alcohol intake.
The researchers examined whether this difference was related to the neural circuit connecting the basolateral amygdala and the medial prefrontal cortex. The basolateral amygdala is involved in processing emotional signals such as anxiety, fear, and stress, and the medial prefrontal cortex plays an important role in assessing situations, controlling impulses, and making decisions.
Using a miniature microscope, the team observed in real time the activity of neurons connecting the amygdala and the prefrontal cortex while the mice freely moved and chose water or alcohol. In socially isolated males, that neural circuit was excessively activated, and this change was closely associated with increased alcohol intake.
Next, the researchers tested whether activation of this circuit merely accompanied higher drinking or actually caused changes in drinking behavior. When they artificially activated the circuit in non-isolated male mice, the brain's response to alcohol became similar to that of isolated males; conversely, when they suppressed the circuit's activity in males that lived alone, alcohol intake decreased.
Reesha Patel of Northwestern University Feinberg School of Medicine, who led the study, said, "This is the first time we have identified a specific brain circuit that can explain how social isolation increases drinking in males," adding, "It can offer a more concrete biological target to understand isolation-related alcohol misuse and to develop future treatments."
However, this is a preclinical study in mice, and the results cannot be applied to people as they are. The researchers added, "Human drinking is simultaneously influenced by diverse factors such as social environment and culture, an individual's mental health, and economic factors," and "We plan to examine what keeps a specific brain circuit persistently overactive under social isolation and why males and females show different responses."
References
Nature Neuroscience (2026), DOI: https://doi.org/10.1038/s41593-026-02413-x