Background In numerous surveys the prevalence of depressive symptoms in adolescents has been examined in single sites and at one time point. Aims We examined depressive symptoms among adolescents aged 10-19 years in four different large school samples including two cohorts over a 10-year period in different locations in the same health region in central Norway including a total of 5804 adolescents. Two cohorts were retested within a 1-year time period to predict high versus low depressive symptom scores. Changes over a 6-year period in depressive symptom levels were examined in two of the samples of 12-14-year olds. Methods Depressive symptoms were estimated by the 13-item Short Mood and Feelings Questionnaire (SMFQ). Covariates were student age, sex, school size and location. Results "Miserable or unhappy", "Tired", "Restlessness" and "Poor concentration" were the most commonly reported depressive symptoms. Depressive symptom levels and proportions of high scoring students were consistently higher among girls, in particular in mid and late adolescence. Poisson regression analysis showed that all SMFQ items significantly predicted total scores for the whole sample, while sex (girls having a higher risk) emerged as a consistent 1-year predictor of high depressive symptom levels. Conclusions The SMFQ constitutes a short, practical and feasible measure. We recommend that this standardized measure should be used in the assessment of depressive symptoms among adolescents in school, primary care and clinical settings but also to evaluate treatment outcome. High scorers should be evaluated in subsequent clinical interviews for the presence of a depressive disorder.
Keywords: Adolescence; Depressive symptoms; Epidemiology; Longitudinal design..