Editorial: Troubled trajectories - new insights on risk pathways and developmental phenotypes of ADHD and externalizing problems.

We are pleased to present this special issue of JCPP, which brings together a collection of cutting-edge empirical studies that focuses on developmental trajectories and pathways associated with ADHD, conduct problems and other externalizing behaviors. JCPP has had a long-standing focus on theoretically strong prospective longitudinal studies that elucidate behavioral change and outcomes over time, including in the areas of ADHD and externalizing disorders (Kuja-Halkola, Lichtenstein, D'Onofrio & Larsson, 2015; Sonuga-Barke & Halperin, 2010). Keeping with that tradition, all of the papers in this special issue employ a prospective longitudinal design and a focus on changes that unfold over development.