Our first analysis followed the traditional approach to investigate the pathophysiology of mental disorders, including ADHD. This approach selects a specific dysfunction hypothesized to be important for the disorder and performs a comparison between subjects with and without the disorder, aiming to identify characteristics (e.g. genetic traits, changes in brain connectivity) that are, on average, more common in the group affected with the disorder than in the group of controls. Another important attribute of this approach is that the groups are usually defined based on symptoms that tend to cluster together; as a result, sometimes individuals who have different behavioral traits can be included in the same group if the criteria for the disorder (or lack of disorder) contain their behavioral traits (Hyman, 2007).
