Associations between circadian and stress response cortisol in children

Figures & data

Figure 1. Diurnal cortisol concentrations (nmol/L) for each of the four sampling moments (based on average scores over both sampling days). Error bars stand for one standard error above and one beneath the mean of each of the four diurnal sampling moments.

Figure 2. Stress response cortisol concentrations (nmol/L) per sampling moment. Error bars stand for one standard error above and beneath the mean of each of the six stress response sampling moments. Note that this is an adapted figure from Simons et al. (2016). Data are reprinted with permission of the publisher: John Wiley and Sons. License number: 4002560272811.

Table 1. Descriptive statistics of all study variables.

	N	M	SD	Min	Max
Child gender (% girls)	144	47.2
Maternal educational level^a	140	6.78	1.39	3.00	8.00
Total diurnal cortisol (nmol/L)	111	4837.33	1371.71	2518.25	10801.13
Diurnal cortisol decline (nmol/L)	126	12.98	4.96	−0.35	26.00
Total stress cortisol (nmol/L)	134	375.80	169.48	73.80	1474.50
Cortisol stress reactivity^b (nmol/L)	142	0.00	1.00	−1.77	5.15

a Scored from 1 = primary to 8 = university.

b M = 0 and SD =1 because these are standardized residuals.

Table 2. Spearman correlations between all study variables.

	1	2	3	4	5^a
Confounders
1. Child gender
2. Maternal educational level	−.00
Predictors
3. Total diurnal cortisol	−.08	.12
4. Diurnal cortisol decline	−.02	.13	.68***
Outcomes
5. Total stress cortisol^a	−.04	−.05	.24*	.14
6. Cortisol stress reactivity^a	.10	−.12	−.16^+	−.08	.46***

a Log transformed.

+p < .100.

*p < .050.

***p < .001.

Table 3. Results from regressions predicting total stress cortisol and cortisol stress reactivity from the indices of the cortisol circadian rhythm.

	Model 1		Model 2
	B	β	B	β
Total stress cortisol
Step 1
Total diurnal cortisol	<0.01	.59***	<0.01	.56***
Diurnal cortisol decline	−0.01	−.25*	−0.01	−.25*
Step 2
Total diurnal cortisol × Diurnal cortisol decline			<0.01	.05
R^2change	0.21***		<0.01
R^2model	0.21***		0.22***
Cortisol stress reactivity
Step 1
Total diurnal cortisol	< −0.01	−.02	< −0.01	−.02
Diurnal cortisol decline	< −0.01	−.09	< −0.01	−.09
Step 2
Total diurnal cortisol × Diurnal cortisol decline			<0.01	.01
R^2change	0.01		<0.01
R^2model	0.01		0.01

No outliers were removed because Cook’s distances indicated no potentially influential data points.

*p < .050.

***p < .001.

Simons SSH, Cillessen AHN, de Weerth C. (2016). Cortisol stress responses and children’s behavioral functioning at school. Dev Psychobiol 9999:1–8.

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