Fig. 2
From: The effect of depressive symptomatology on the association of vitamin D and sleep
Mediation model (2a: without covariates; 2b: with covariates (age, the BMI score and the season in which vitamin D concentrations had been measured)) showing both the direct effect of serum 25(OH) D concentrations on midsleep time (path coefficient c) and the indirect effect of serum 25(OH) D concentrations on midsleep time mediated through depressive symptomatology (as measured by modified CES-D sum scores) (path coefficient ab) in N = 1252 individuals of the study sample. The figure depicts the unstandardized path coefficients (a,b,c and ab). CES-D: German version of the Centre for Epidemiological Studies Depression Scale (CES-D, [35, 36]) without item 11 representing intensity of sleep problems; serum 25(OH)D: serum 25(OH) D concentration. * p < 0.05