Social separation increases alcohol consumption in rhesus monkeys.

This study used 16 socially reared juvenile rhesus monkeys as subjects to test the hypothesis that social separation promotes alcohol consumption in this species. In the first part of the study, 12 monkeys were intermittently separated from their social groups, while 4 were separated before the beginning of the study and remained continuously separated. Refrigerated water or aspartame-sweetened water (vehicle) containing 6% alcohol (w/v) were presented after 4.5 h of fluid deprivation. Intermittently separated monkeys drank more alcohol during separation than when they were socially housed, and more than the continuously separated monkeys. Stable individual differences in consumption rate developed over repeated separations. These differences were not correlated with consumption of refrigerated water or vehicle, or with differential behavioral (locomotor) responses to social separation. This suggested that some monkeys were predisposed to drink more alcohol than others. The second part of the study determined whether established alcohol/vehicle consumption rates for all 16 monkeys were altered when the monkeys were not water deprived, and then when water and the vehicle were available at the same time as alcohol/vehicle. Among monkeys that drank the most (mean of 2.4 g/kg/h) and the least (mean of 0.8 g/kg/h), alcohol consumption was not affected. These results, combined with previous reports, suggest a neurobiological linkage between genetically based social attachment mechanisms, social stressors, and vulnerability to alcohol abuse and addiction in primates.