Children's mental health symptoms over three decades (1993-2022): a comparison of population-based cross-sectional...

Concerns have been raised about an increase in children's mental health symptoms over the past 30 years, including after COVID-19 lockdowns. Yet, few studies have investigated variations over generations, while considering sex and socioeconomic status. We aimed to address this gap by comparing mental health symptoms (emotional distress, impulsivity/hyperactivity/inattention, disruptive behaviours) reported by classroom teachers of 11-year-olds in three population-based, prospective, representative cohorts in Quebec, Canada. Analyses included 1665 (83%) of the Quebec Longitudinal Study of Kindergarten Children, in 1993; 1305 (62%) of the Quebec Longitudinal Study of Child Development, 2009; and 3871 (100%) of the Quebec Survey of Child Development in Kindergarten, 2022; ~50% boys. Teacher-rated symptoms on the validated Social Behavior Questionnaire showed higher scores of emotional distress and impulsive/hyperactive/inattentive symptoms in 2022 than 2009, and higher in 2009 than 1993 (very small-to-small effect sizes: Cohen's d 0.12 and 0.26 for emotional distress, 0.06 and 0.25 for impulsive/hyperactive/inattentive symptoms, respectively; P < 0.001). Disruptive behaviour symptoms scored lower in 2022 than 2009, though higher in 2009 than 1993, with very small effect sizes (Cohen's d: -0.15 and 0.09, respectively). Boys presented more impulsive/hyperactive/inattentive and disruptive behaviour symptoms than girls; girls showed more emotional distress than boys. Children from economically disadvantaged households (lowest 20% of income distribution) presented higher symptoms rates than advantaged children. These findings provide novel and timely evidence about variations in children's mental health symptom rates over three decades, underscoring the need for preventive interventions as early as elementary school, tailored differentially for boys and socioeconomically disadvantaged children.