Swedish SDQ Norms for Internalizing and Externalizing Problems in Preschoolers

The Strengths and Difficulties Questionnaire (SDQ) is one of the most widely used instruments for assessing mental health in children. While Swedish norms for the SDQ have previously been published for children aged 3-5 years, percentile-based cutoffs for the broader internalizing and externalizing scales are still lacking. This study aimed to extend existing Swedish SDQ norms by providing population-based cutoffs for the composite internalizing and externalizing scales in preschool children. Data were derived from a large, population-based sample of children aged 3-5 years in Uppsala County, including ratings from both parents and preschool teachers. Internalizing and externalizing scores were computed by summing the relevant SDQ subscales, and percentile cutoffs were calculated by age, gender, and rater, with the 80th and 90th percentiles used to indicate borderline and abnormal levels of difficulties. Cutoff values were consistently lower in teacher ratings than in parent ratings, and across most age groups and scales girls had lower cutoff values than boys. Age variation was modest, with a general tendency towards slightly lower cutoff scores with increasing age. These new normative cutoffs extend the Swedish SDQ norms for preschoolers to include the widely used composite scales and support more comprehensive use of the SDQ in both clinical screening and research on young children's mental health.