Adolescents’ personality and sex, age, socioeconomic status in explaining mental health: A representative Swedish national study

• This 2024 national study compared individual personality traits and demographic variables (i.e., sex, age, socioeconomic status) in explaining mental health in a large representative sample of Swedish 15 to 18-year-olds (N = 10,288). • Big Five neuroticism was reported higher in females than males (d = 0.68), and sex differences in general anxiety (GAD-7) was equivalent to 3 out of 4 females being higher than the male mean. • Individual differences in Big Five personality explained mental health approximately 10 times more than demographic group differences. The present study compared individual personality traits and demographic variables, i.e. sex, age, and socioeconomic status, in explaining mental health in a large representative adolescent Swedish high school survey. This data collection on 15- to 18-year-olds (N = 10,288, response rate 79 %) was conducted in 2024 and included, for the first time, a brief Big Five personality measure (Ten Item Personality Inventory; TIPI) together with 3 diverse mental health measures (General Anxiety Disorder, GAD-7; Daily dysfunction; and Global satisfaction with self). Individual differences in the Big Five personality traits, particularly neuroticism, explained mental health approximately 10 times more than demographic differences. Females reported higher neuroticism (d = 0.68) and lower mental health across all study measures (d Mean = -0.62) than males. Differences in general anxiety (GAD-7) equated to 3 out of 4 females being higher than the male mean. Age and socioeconomic status showed trivial effects. We discuss study limitations and recommend taking individual differences in personality into account in adolescent mental health research.