The causes of psychiatric disorders are poorly understood. Now, in work led by researchers at McGill University in Canada, there is evidence that a wide range of early-onset psychiatric problems (from depression, anxiety, and addictions; to dyslexia, bulimia, and ADHD) may be largely due to the combination of just three factors. The first is biological—in the form of individual variability in the brain’s dopamine reward pathway. The second is social—and points to the important role of early childhood neglect or abuse. And the third is psychological—and relates to temperament, and particularly to tendencies toward impulsivity and difficulty controlling emotions. These findings have implications for understanding both the causes of a wide range of psychiatric disorders and the features worth targeting in early intervention efforts.