Box Figure 1

Four theoretical scenarios of the association of school timing and/or baseline chronotype (in 1st year of high school) with ΔChronotype (MSFsc 5th year-MSFsc 1styear). (a) Only school timing is associated. (b) Only the baseline chronotype is associated. (c) Baseline chronotype and school timing are additively associated. (d) Baseline chronotype and school timing interact. The graphs on each scenario represent the expected developmental change in chronotype (i.e. ΔChronotype) as a function of the baseline chronotype (i.e. 1st year MSFsc) for each school timing. A zero value on the vertical axis indicates no change in chronotype from 1st to 5th year. Positive or negative values indicate that chronotype is delayed or advanced, respectively, in 5th compared to 1st year. Each colored line represents the linear relation between ΔChronotype and baseline chronotype for each school timing. Grey arrows represent ΔChronotype for three representative baseline chronotypes (early, intermediate and late), the base of the arrows represent students’ chronotype in their 1st year (i.e. the baseline chronotype) and the arrowheads represent students’ chronotype in their 5th year.