Table 2. Display of obligatory and optional variables included at the respective steps of model development.

Model Step	Obligatory predictors	Optional covariates
Step 1	-	-
Step 2	• time of day • workday/weekend • ith assessment • loneliness Ti-1 • social contact Ti-1—i-2	• affect Ti-1 • worry Ti-1 • interactions between level-1 predictors
Step 3	• gender • age • trait loneliness	• depression
Step 4	loneliness Ti-1 slope	possible level-1 variable slopes: • day/time of day • psychological states • behavioral predictors
Step 5	Includes all conducted cross-level interaction tests: • trait loneliness*loneliness Ti-1 • depression*loneliness Ti-1 • gender*loneliness Ti-1 • age*loneliness Ti-1 • average_loneliness*loneliness Ti-1 • average_affect*loneliness Ti-1