Chronic Stress in Early Life Causes Anxiety Later

In experiments to assess the impacts of social stress upon adolescent mice, both at the time they are experienced and during adulthood, a Cold Spring Harbor Laboratory team conducted many different kinds of stress tests and means of measuring their impacts. The research indicates that a 'hostile environment in adolescence disturbs psychoemotional state and social behaviors of animals in adult life,' the team says.

The tests began with 1-month-old male mice -- the equivalent, in human terms of adolescents -- each placed for 2 weeks in a cage shared with an aggressive adult male. The animals were separated by a transparent perforated partition, but the young males were exposed daily to short attacks by the adult males. This kind of chronic activity produces what neurobiologists call social-defeat stress in the young mice. These mice were then studied in a range of behavioral tests.

"The tests assessed levels of anxiety, depression, and capacity to socialize and communicate with an unfamiliar partner," explains Enikolopov. These experiments showed that in young mice chronic social defeat induced high levels of anxiety helplessness, diminished social interaction, and diminished ability to communicate with other young animals. Stressed mice also had less new nerve-cell growth (neurogenesis) in a portion of the hippocampus known to be affected in depression: the subgranular zone of the dentate gyrus.

http://www.sciencedaily.com/releases/2014/03/140327123654.htm
Full text at PLoS ONE: Extended Effect of Chronic Social Defeat Stress in Childhood on Behaviors in Adulthood