Loneliness Drives Male Mice to Drink More, Female Mice to Drink Less

Social isolation may motivate men to drink more alcohol while suppressing the urge to drink in women, according to a study led by researchers from Northwestern University and the Salk Institute for Biological Studies in the US, published in Nature Neuroscience.

Roughly one in six people worldwide experience loneliness, a condition that affects both mental state and physical health. Studies in both animals and people have consistently shown that heavy drinking is strongly linked to social isolation, suggesting a connection between loneliness and the urge to drink, though the underlying brain mechanism was unclear.

To find that mechanism, the researchers separated mice from their community and then offered each mouse a choice between water and a 15% alcoholic drink. Using electrophysiology and calcium imaging, they monitored brain regions associated with stress responses, emotional processing and socializing, and found a circuit between the basolateral amygdala and the medial prefrontal cortex that correlated with alcohol consumption. Triggering this pathway with light, a technique called optogenetics, confirmed its role in causing the mice to drink.

While activity across these brain regions tracked with alcohol consumption in both sexes, only male mice were encouraged to drink more when isolated; separated female mice actually drank less. There were also variations among individual mice, with lower-ranked mice in the social hierarchy showing higher baseline excitability in the circuit.

"This is the first study to identify a specific brain circuit that explains how social isolation can drive increased alcohol use in males, marking a major advance for the field," said Reesha Patel, a neuroscientist at Northwestern University and one of the study's researchers.