Are teens uniquely susceptible to long-term effects of stress?
or technically,
Adolescent Chronic Unpredictable Stress Exposure Is a Sensitive Window for Long-Term Changes in Adult Behavior in Mice.
[See Original Abstract on Pubmed]
Authors of the study: Nicole L Yohn & Julie A Blendy
Stress happens. Whether it’s a dead car battery or a looming work deadline, stress is a fact of life. However, the types of stressors we experience and how they might affect us are constantly changing. Adolescence is one stage of life where these changes are particularly apparent. Most of us can appreciate how the nature of stressors change during adolescence (school pressures, dating and friendships, availability of drugs/sex/alcohol, huge physical and emotional developments, etc.), but less appreciated are the ways in which teens may be uniquely susceptible to the long-term and detrimental effects of these stressors.
This question of if and why adolescents are especially sensitive to stress shaped Nicole Yohn’s research at the University of Pennsylvania in the laboratory of Dr. Julie Blendy. Previous research has shown that human brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. development is not fully completed until about the age of 25. In this sense, our brainsThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. are still undergoing tremendous remodeling during our teenage years. Nicole wondered if exposure to stress during this period of continuing brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. development may contribute to the increase in mental disorders, like anxiety, depression, and drug abuse, which often emerge during these years. This was an important question-- even though there’s plenty of research linking stress to mental disorders, there are very few studies looking at how the two are connected. Nicole set out to bridge that gap.
One of the most important (and most frustrating) aspects of stress is that it’s both chronic and unpredictable. In order to best model these aspects of stress in the lab, Nicole created a mouse model and designed her experiment such that each mouse was exposed to three different types of stressors a day for twelve consecutive days. These stressors consisted of things like food restriction, exposure to cold temperatures, isolation, and other unpleasant situations. To ask whether exposure to stress during adolescence is more damaging than exposure to stress during adulthood, Nicole compared two groups of mice-- one that faced these chronic and unpredictable stressors during puberty and one that experienced the stressors during adulthood. Both groups of mice were tested for behaviors associated with anxiety and depression, the most prevalent stress-related disorders.
So, does stress during particular stages of development alter susceptibility to mental illness? Nicole found that it seems to depend on exactly which mental illness we’re talking about. For example, Nicole observed depression-like behaviors in all mice exposed to stress, regardless of whether they experienced that stress during puberty or adulthood. In contrast, anxiety behaviors only appeared if stress occurred during adolescence, not adulthood. The sex of the mice also seemed to be an important factor in effects of stress on behavior. In one behavioral assessment, female mice showed more anxiety than males. This might mean that how we respond to stress may have something to do with sex-specific hormonesA substance produced in the body that controls or regulates the activity of certain cells or organs. Many hormones are produced by special glands and travel through the blood to reach the location in the body where they act..
Speaking of hormonesA substance produced in the body that controls or regulates the activity of certain cells or organs. Many hormones are produced by special glands and travel through the blood to reach the location in the body where they act. and chemicals, Nicole wanted to look for a chemical that might underlie the different effects stress has on adolescents versus adults. One chemical she chose to investigate was corticotropin releasing factor (Crf) -- a hormoneA substance produced in the body that controls or regulates the activity of certain cells or organs. Many hormones are produced by special glands and travel through the blood to reach the location in the body where they act. that’s released in the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. when we feel stressed. Crf is responsible for the extra alertness or the feeling of butterflies in our stomachs we might notice before doing something important, like giving a presentation. While a short-term boost of Crf might be helpful in focusing our attention on the task at hand, too much Crf can be a bad thing. When looking at Crf levels in the brainsThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. of her mice, Nicole found increases only in mice that were exposed to stress during adolescence. Interesting, right? It seems like this increase in Crf could be what’s causing the development of anxiety in adolescent but not adult animals.
What do we know for sure? Nicole’s work suggests that mice are especially susceptible to stress during adolescence. She also showed that being female might make you even more susceptible to the long-lasting effects of stress. While more research is needed to determine whether these findings hold true for humans, Nicole has established a good model for future studies to look into how stress affects us throughout our lives, and how we might be able to prevent or lessen the damage it causes.
This question of if and why adolescents are especially sensitive to stress shaped Nicole Yohn’s research at the University of Pennsylvania in the laboratory of Dr. Julie Blendy. Previous research has shown that human brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. development is not fully completed until about the age of 25. In this sense, our brainsThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. are still undergoing tremendous remodeling during our teenage years. Nicole wondered if exposure to stress during this period of continuing brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. development may contribute to the increase in mental disorders, like anxiety, depression, and drug abuse, which often emerge during these years. This was an important question-- even though there’s plenty of research linking stress to mental disorders, there are very few studies looking at how the two are connected. Nicole set out to bridge that gap.
One of the most important (and most frustrating) aspects of stress is that it’s both chronic and unpredictable. In order to best model these aspects of stress in the lab, Nicole created a mouse model and designed her experiment such that each mouse was exposed to three different types of stressors a day for twelve consecutive days. These stressors consisted of things like food restriction, exposure to cold temperatures, isolation, and other unpleasant situations. To ask whether exposure to stress during adolescence is more damaging than exposure to stress during adulthood, Nicole compared two groups of mice-- one that faced these chronic and unpredictable stressors during puberty and one that experienced the stressors during adulthood. Both groups of mice were tested for behaviors associated with anxiety and depression, the most prevalent stress-related disorders.
So, does stress during particular stages of development alter susceptibility to mental illness? Nicole found that it seems to depend on exactly which mental illness we’re talking about. For example, Nicole observed depression-like behaviors in all mice exposed to stress, regardless of whether they experienced that stress during puberty or adulthood. In contrast, anxiety behaviors only appeared if stress occurred during adolescence, not adulthood. The sex of the mice also seemed to be an important factor in effects of stress on behavior. In one behavioral assessment, female mice showed more anxiety than males. This might mean that how we respond to stress may have something to do with sex-specific hormonesA substance produced in the body that controls or regulates the activity of certain cells or organs. Many hormones are produced by special glands and travel through the blood to reach the location in the body where they act..
Speaking of hormonesA substance produced in the body that controls or regulates the activity of certain cells or organs. Many hormones are produced by special glands and travel through the blood to reach the location in the body where they act. and chemicals, Nicole wanted to look for a chemical that might underlie the different effects stress has on adolescents versus adults. One chemical she chose to investigate was corticotropin releasing factor (Crf) -- a hormoneA substance produced in the body that controls or regulates the activity of certain cells or organs. Many hormones are produced by special glands and travel through the blood to reach the location in the body where they act. that’s released in the brainThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. when we feel stressed. Crf is responsible for the extra alertness or the feeling of butterflies in our stomachs we might notice before doing something important, like giving a presentation. While a short-term boost of Crf might be helpful in focusing our attention on the task at hand, too much Crf can be a bad thing. When looking at Crf levels in the brainsThe brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. of her mice, Nicole found increases only in mice that were exposed to stress during adolescence. Interesting, right? It seems like this increase in Crf could be what’s causing the development of anxiety in adolescent but not adult animals.
What do we know for sure? Nicole’s work suggests that mice are especially susceptible to stress during adolescence. She also showed that being female might make you even more susceptible to the long-lasting effects of stress. While more research is needed to determine whether these findings hold true for humans, Nicole has established a good model for future studies to look into how stress affects us throughout our lives, and how we might be able to prevent or lessen the damage it causes.
About the brief writer: Kara McGaughey
Fascinated by the long-standing linguistic connection between the gut and the brain ("gutsy," "gut feeling," "gut instinct," etc.), Kara is using her second year in NGG to examine the interplay between microbiota and brain development.