Fig. 1

Item–factor, factor–total, and discriminant correlations between the SQQ, PHQ-4, and SRHQ (N = 595). Note: Spearman correlations, T1 Time 1, T2 Time 2, SQQ Sleep Quality Questionnaire, SQQ01-10 item 1–10, SDS Sleep Difficulty Subscale, DSS Daytime Sleepiness Subscale, DSS (-) item 2 excluded from the DSS, SQQ-9 item 2 excluded from the SQQ, GAD Generalized Anxiety Disorder, PHQ Patient Health Questionnaire, SRHQ Self-Rated Health Questionnaire