Loneliness and Its Relation to Mental Health in the General Population: Validation and Norm Values of a Brief Measure

•Our study is the first confirming measurement invariance across gender and age for one of the most established loneliness scale in a German representative sample.•Women reported overall higher levels of loneliness, apart from the middle age (40-49 years), when men's loneliness peaked.•Loneliness was positively correlated with depressiveness, anxiety, perceived stress, hopelessness, suicidality, and fatigue, and negatively correlated with life satisfaction.•Differentiated norm values are provided for gender and age.