Teens who experience sleep difficulties are more reactive to stress, which in turn, could contribute to greater academic, behavioral, and health problems, according to a new study led by the University of Alabama at Birmingham (UAB).
Previous research has shown that nearly 70 percent of U.S. adolescents do not get enough sleep. It is also known that insufficient sleep and sleep problems eventually lead to cognitive problems and poor physical health over time.
Researchers believe this may be due to disruptions in the hypothalamic-pituitary-adrenal axis, or the HPA axis, a key part of the neuroendocrine system that regulates reactions to stress and helps maintain many body processes.
While the association between sleep and the HPA axis has been well studied in both children and adults, much less is known about this link during the teen years. This is surprising as puberty represents a key growth period in which both sleep and the HPA axis are undergoing significant developmental changes.
In the current study, researchers from UAB and Arizona State University sought to further explore the relationship between sleep and reactivity to stress, specifically as it relates to HPA-axis activity, in teens.
They examined two dimensions of sleep — sleep duration and sleep problems from the perspectives of teens and their parents, as well as cortisol levels before and after social stress. The team also looked for any differences between genders.
“We chose to look at sleep patterns in urban African-American adolescents, due to information we understood from earlier research in the field,” said Dr. Sylvie Mrug, a psychology professor in UAB’s College of Arts and Sciences.
“This particular population is more likely to experience insufficient sleep, and their functioning is more negatively affected by lower sleep quality, so we knew that finding results for this demographic could be especially important.”
The researchers recruited 84 adolescents with an average age of 13. During their visit to the research lab, the young participants were given the children’s version of a common stress test, called the Trier Social Stress Test, which involves speaking and computing mental math problems in front of an audience. Saliva samples were taken from each participant in order to test cortisol levels before and after the stress test.
Participants then reported on their bed times and wake times and any sleep problems, such as insomnia, daytime sleepiness and general sleep quality, during a regular week. Parents of the teens were asked to report on their children’s sleep as well.
The most commonly reported sleep problems were as follows: the need for multiple reminders to get up in the morning, not having a good night’s sleep, feeling tired or sleepy during the day, and not being satisfied with their sleep.
The researchers measured the cortisol levels of the participants. Cortisol release during and after the stressful lab test was higher for those who reported more sleep problems and longer sleep duration, and whose parents reported longer sleep duration.
“The result of higher cortisol levels in adolescents experiencing sleep problems was exactly what we expected to see,” Mrug said. “We were, however, surprised that longer sleep duration predicted a stronger cortisol response, because previous studies linked shorter sleep duration with higher cortisol levels.”
“Generally, less sleep is related to poor outcomes, not the other way around. In this case, this unexpected result could be explained by considering that longer sleep duration does not necessarily reflect higher-quality sleep, but instead may serve as another indicator of sleep problems, at least among urban adolescents.”
The effects of sleep problems on greater cortisol release during stress were stronger in girls than in boys, suggesting that young females may be more sensitive to disrupted and poor quality sleep.
“Overall, the results of our study confirm what we originally hypothesized — that sleep problems induce greater response to stress in adolescents,” Mrug said. “It’s important that we know this, because the enhanced and prolonged activation of the HPA axis in response to stress could contribute to more health problems.”
The findings are published online in the journal Physiology and Behavior.