There is increasing evidence of comorbidity which transcends distinct psychiatric diagnoses, as well as shared genetic influences found across disorders. My research will examine whether there are common alterations in brain structure across externalising (ADHD, substance dependence, conduct disorder) and internalising (anxiety, mood) disorders, or whether alterations are disorder-specific. Using data from international research groups within the ENIGMA consortium, this project will be the largest and most comprehensive neuroimaging study of transdiagnostic psychopathology in children and adolescents to date. I hope that the findings will have implications for our diagnostic systems, and inform future prevention and intervention strategies.