Prevalence of depressive disorders and associated demographic characteristics in Shandong: An epidemiological investigation

•The largest Epidemiological Survey of Mental Disorders conducted in Shandong•A multi-stage stratified cluster sampling method and a two-stage screening process•The adjusted prevalence of depressive disorders was 4.86%.•Age, gender, occupation, education, marital status, and urban/rural living were associated with the prevalence.•40.35% of patients had moderate or severe functional impairment.