Stability of Mental Health Problems across Middle Childhood — Results from the Bergen Child Study Tormod Bøe, A. J. Lundervold, T. Torsheim, K. M. Stormark January 2010 Cite ⛔ no doi found Related Delayed Sleep Phase Syndrome in Adolescents: Prevalence and Correlates in a Large Population Based Study The Strengths and Difficulties Questionnaire (SDQ): Factor Structure and Gender Equivalence in Norwegian Adolescents