Descriptive characteristics of study participants.

<p>A total sample size of N = 50 was included in the analysis. Descriptive data are presented in means (M) and standard deviations (SD). Absolute numbers of participants are given (N) and expressed as percentage (%).</p><p><b>Abbreviations:</b> means (<i>M</i>); standard deviation (<i>SD</i>), brain-derived neurotrophic factor (BDNF); Insomnia Severity Index (ISI); Perceived Stress Scale (PSS); restless legs syndrome (RLS), periodic limb movement (PLM).</p

Correlation between serum BDNF levels and scores on the <i>Perceived Stress Scale</i> (PSS) by insomnia severity groups according to the <i>Insomnia Severity Index</i> (ISI).

<p>Analyses showed a significant correlation (partial correlation controlled for smoking) between BDNF and stress only in subjects with no insomnia (<i>r_p</i> = −0.511, p = 0.013) compared to subjects with sub threshold (<i>r_p</i> = 0.069, <i>p</i> = 0.814) or clinical insomnia (<i>r_p</i> = 0.199, <i>p</i> = 0.608). White squares represent subjects with no insomnia, black circles represent subjects with sub threshold and black triangles represent subjects with clinical insomnia. (Inset) Mean serum BDNF levels of the insomnia severity groups. Plotted means and standard errors estimated by ANCOVA with serum BDNF as dependent variable, insomnia severity group as independent variable and smoking as covariate. For all three insomnia severity groups the overall effect on serum BDNF was not significant (<i>F</i>(2) = 2.67; <i>p</i> = 0.080). Contrasts showed that serum BDNF levels in the group with no insomnia were significantly higher compared to the groups reporting sub threshold and clinical insomnia (<i>F</i>(1) = 5.33; <i>p</i> = 0.026); (no insomnia n = 24; sub threshold insomnia n = 16, clinical insomnia n = 10). * Denotes statistical significance at <i>p</i><0.05</p

Stress experience in subjects suffering from current insomnia.

<p>Correlation between insomnia severity score (indicated by the <i>Insomnia Severity Index</i> (ISI)) and stress perception (indicated by the <i>Perceived Stress Scale</i> (PSS)). Analysis showed a significant correlation between scores on the ISI and the PSS across the whole sample (<i>r_p</i> = 0.548, <i>p</i><0.001). * Denotes statistical significance at <i>p</i><0.05.</p

Baseline characteristics.

<p>Mann Whitney U tests were performed; all data are expressed as means±SD.</p

Additional file 1: of Validation of the German version of the insomnia severity index in adolescents, young adults and adult workers: results from three cross-sectional studies

Validation of the German Version of the Insomnia Severity Index_Supplementary Online Material. Insomnia Severity Index – Deutsche Übersetzung (German translation). This file provides the German translation of the Insomnia Severity Index, as well as a guide for (a) calculating an overall index and (b) interpreting the overall score. (DOCX 81 kb

Body composition and resting energy expenditure (measured by BIA and indirect calorimetry, respectively).

<p>Mann Whitney U tests were performed; all data are expressed as means±SD; *indicates statistical significance.</p

Correlation of salivary cortisol, baseline characteristics, glucose and lipid metabolism as well as catecholamines; filled circles represent controls, filled triangles represent insomniacs; p values including all participants are presented.

<p>Correlation of salivary cortisol, baseline characteristics, glucose and lipid metabolism as well as catecholamines; filled circles represent controls, filled triangles represent insomniacs; p values including all participants are presented.</p

Visceral and subcutaneous adipose tissue volume, liver fat content, intramyocellular lipid content (MR spectroscopy) and insulin sensitivity (euglycaemic hyperinsulinaemic clamp).

<p>Mann Whitney U tests were performed; all data are expressed as means±SD.</p

Parameters of sleep continuity and sleep architecture (polysomnographic study).

<p>Mann Whitney U tests were performed; all data are expressed as means±SD; *indicates statistical significance.</p

Midnight and morning salivary cortisol concentrations in insomniacs and controls.

<p>Midnight values were significantly higher in insomniacs than in controls (p = 0.02), whereas morning values did not differ significantly (p = 0.18).</p