A new study using mice has revealed that the root of psychiatric disorder attention deficit/hyperactivity disorder (ADHD) might be found in an overactive protein which is responsible for regulating the dopaminergic pathways. Although ADHD is typically seen as a condition affecting teenagers, it also affects around 5% of adults, and this breakthrough could help scientists to progress with finding it’s as yet unknown cause. The discovery has been added to a growing body of evidence which suggests that dopamine, a neurotransmitter involved in the brain’s reward-motivation system, could trigger the disorder. "The genetically modified mice that we generated present interesting features such as hyperactivity and altered nesting capacities that might be related to attention deficit, and possibly altered impulsivity," Marc Flajolet, a senior research associate at the Rockefeller University which engaged in the research. "We believe that over expression of CK1δ [an enzyme called casein kinase] induces some developmental steps that resemble what might be happening in ADHD patients and therefore we propose that the CK1δ-overexpressing mice are a model for this disorder," says Flajolet. "It will be interesting to investigate if CK1 could be the origin of developmental defects in humans that lead to ADHD."