Social isolation during adolescence causes increased generalised anxiety-like behaviour in male rats and increased sociability in male and female rats.

As one of the main characteristics of adolescence is the increased desire for social interaction and formation of meaningful relationships, it represents a particularly vulnerable period for social stressors. Moreover, social isolation during adolescence can significantly alter brain function and increase the likelihood of anxiety disorders in early adulthood. The aim of this retrospective meta-analysis and prospective behavioural experiment was to investigate whether chronic isolation stress during adolescence causes generalised and social anxiety-like behaviour in rodents. The meta-analysis of previously published data showed that social isolation during adolescence leads to an increase in generalised anxiety-like behaviour exclusively in male isolated rodents and has ambiguous effect on social anxiety-like behaviour. In the subsequent prospective experiment, Sprague-Dawley rats of both sexes were subjected to six weeks of social isolation and their behaviour was investigated in the open field, elevated plus maze, and three-chamber test. Consistent with the retrospective literature analysis, social isolation in adolescence increased generalised anxiety-like behaviour exclusively in males, as indicated by a decrease in time spent in the centre of the open field and open arms of the elevated plus maze, compared to controls. Both male and female isolated rats showed an increase in sociability in the three-chamber test, as indicated by the increase in the preference ratio for social versus neutral stimuli, compared to controls. Altogether, social isolation leads to an increase in generalised anxiety-like behaviour exclusively in males and to increased sociability in both males and females.