The Lasting Effects of Chronic Stress in Adolescence

Research assesses the impact of stress experienced in adolescent mice during adulthood.

March 27, 2014—Exposure to hostile environments during adolescents has significant emotional and behavioral consequences in adult life, according to a research team led by Grigori Enikolopov of Cold Spring Harbor Laboratory (CSHL).

Adolescent mice were first exposed to an aggressive adult male with the only separation being a transparent, punctured divider. Then, the adolescents experienced chronic social defeat stress by lifting the divider for a short increment to allow minor attacks by the aggressive adult mice. After measuring the impact of these different stress tests, the research indicates that a “hostile environment in adolescence disturbs psychoemotional state and social behaviors of animals in adult life,” the team states.

Adolescent mice exposed to hostile environments experience notable emotional and behavioral consequences in adult life.

This research confirms that adolescents are at a greater risk than other age groups to develop psychoemotional disorders, including anxiety or depression. The Cold Spring Harbor Laboratory scientists have indicated a link between certain kinds of early stress and dysfunction in the neuroendocrine system. The neuroendocrine system is made up of the nervous system and the endocrine system, which work together to control body functions such as growth, metabolism, reproduction, and response to stress or injury.

The tests began with 1-month-old male mice, which, in terms of human age, would be considered the adolescent stage. Each of these mice was put in a cage separated by a transparent, perforated division between them and the aggressive male and were daily exposed to short attacks. Then, these mice were examined in a range of behavioral tests to determine the impact of the chronic, adolescent stress. According to the lead scientists, Dr. Enikolopov, “the tests assessed levels of anxiety, depression, and capacity to socialize and communicate with an unfamiliar partner.”

It was found that in young mice, induced stress augmented levels of anxiety, helplessness, diminished social interaction, and an inability to communicate with other young animals. Furthermore, mice exposed to the hostile environment in adolescents had less new nerve-cell growth in a part of the hippocampus that is known to be involved in depression.

Another group of adolescent male mice was exposed to similar social stress, but was then placed in a stress-free environment for several weeks. After the rest period, most of the behaviors that resulted from the hostile environment went away. Furthermore, nerve-cell growth rate returned to normal. Dr. Enikolopov asserts, “This shows that young mice, exposed to adult aggressors, were largely resilient biologically and behaviorally.”

However, some of these resilient mice still showed abnormal levels of anxiety and were observed to be more aggressive in their social interactions. Ultimately, as observed by Dr. Enikolopov, “the exposure to a hostile environment during adolescence had profound consequences in terms of emotional state and the ability to interact with peers.”

Kayleigh Makoid

Dickinson College

Sources:

Irina L. Kovalenko, Anna G. Galyamina, Dmitry A. Smagin, Tatyana V. Michurina, Natalia N. Kudryavtseva, Grigori Enikolopov. Extended Effect of Chronic Social Defeat Stress in Childhood on Behaviors in Adulthood. PLoS ONE, 2014; 9 (3): e91762 DOI: 10.1371/journal.pone.0091762

Cold Spring Harbor Laboratory. (2014, March 27). Chronic stress in early life causes anxiety, aggression in adulthood, neurobiologists find. ScienceDaily. Retrieved March 30, 2014 from www.sciencedaily.com/releases/2014/03/140327123654.htm

About Kayleigh Makoid