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Int. J. Environ. Res. Public Health 2017, 14(5), 475; doi:10.3390/ijerph14050475

Stress in School. Some Empirical Hints on the Circadian Cortisol Rhythm of Children in Outdoor and Indoor Classes

Department of Cultural Studies and Languages, University of Stavanger, 4036 Stavanger, Norway
Department of Sports and Health Sciences, Technical University of Munich, Arcisstr. 21, 80333 Munich, Germany
Department of Mathematics and Natural Sciences, University of Stavanger, 4036 Stavanger, Norway
Faculty of Social Science, Media and Sport, Johannes Gutenberg University, Mainz Saarstr. 21, 55099 Mainz, Germany
Department of Clinical Psychology, Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, J 5, 68159 Mannheim, Germany
Author to whom correspondence should be addressed.
Received: 16 February 2017 / Revised: 13 April 2017 / Accepted: 25 April 2017 / Published: 30 April 2017
(This article belongs to the Section Environmental Health)
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This prospective longitudinal survey compared the stress levels of students taught using an outdoor curriculum in a forest, with children in a normal school setting. We were especially interested in the effect outdoor teaching might have on the children’s normal diurnal cortisol rhythm. 48 children (mean age = 11.23; standard deviation (SD) = 0.46) were enrolled, with 37 in the intervention group (IG), and 11 in the control group (CG). The intervention consisted of one full school day per week in the forest over the school year. Stress levels were measured in cortisol with three samples of saliva per day. Furthermore, the data allowed for statistical control of physical activity (PA) values. For data analysis, we used a linear mixed-effects model (LMM) with random intercept and general correlation matrix for the within-unit residuals. The LMM yields that IG have expected greater decline of cortisol compared to CG; rate 0.069 µg/L vs. 0.0102 µg/L (log-units/2 h), p = 0.009. PA does not show a statistically significant interaction with cortisol (p = 0.857), despite being higher in the intervention group (p < 0.001). The main effect in our measures was that the IG had a steady decline of cortisol during the school day. This is in accordance with a healthy child’s diurnal rhythm, with a significant decline of cortisol from morning to noon. This effect is constant over the school year. The CG does not show this decline during either measurement day. Further research is needed to fully explain this interesting phenomenon. View Full-Text
Keywords: stress; cortisol; physical activity; outdoor learning; mixed effect model stress; cortisol; physical activity; outdoor learning; mixed effect model

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Dettweiler, U.; Becker, C.; Auestad, B.H.; Simon, P.; Kirsch, P. Stress in School. Some Empirical Hints on the Circadian Cortisol Rhythm of Children in Outdoor and Indoor Classes. Int. J. Environ. Res. Public Health 2017, 14, 475.

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