The differential diagnosis of ADHD

Diagnostic issues in ADHD are examined from two perspectives. Firstly the long-term outcome of ADHD is one indicator of predictive validity of the concept and of its importance. At the same time, the role of comorbid conditions is fundamental to the prognosis of children with ADHD and emphasises the need for thorough assessment and careful differential diagnosis. The range of adult sequelae of ADHD is so broad as to have major implications for the delineation of adult ADHD, and suggestions are made as to how it cannot just be seen as a direct translation of the childhood symptoms. Given the high genetic component to ADHD, our work in ATAP (the Australian Twin ADHD Project) is used to examine three issues in the diagnosis of ADHD, namely that it is inherited as a behavioural dimension, not as a discrete category that there is some genetic and behavioural independence of the Hyperactivity-Impulsivity and Inattention symptom clusters, and that ADHD should not be seen as a consequence of learning problems (or the reverse). Because the concept of ADHD has undergone so many revisions since 1980, there remains much scope for input to a more definitive formulation with particular reference to age and gender differences.