To date, diagnosing Attention Defi cit Hyperactivity Disorder remains indeed one of the most controversial issues in contemporary psychiatry and behavioural sciences. Most of the conceptual problems regarding the validity of this diagnostic category arise from the heterogeneity of syndromal pictures and the high rate of comorbidity observed in subjects diagnosed with ADHD at all stages of the longitudinal course of the disorder. In this regard, DSM 5 increased complexity by allowing a diagnosis of comorbidity between ADHD and autism spectrum (...) disorders while these two diagnoses were mutually exclusive in DSM-IV-TR. (shrink)