In the last decades the concept of bipolar disorder was subjected to many revisions. The complexity in diagnosing mood disorders, on the other hand, stems from the problem to delineate the boundary of these morbid conditions. The current nosographic approach is limited by the lack of attention given to the natural course and to the longitudinal and family characteristics of patients suffering of mood disorders. Considering these limits, some authors developed different nosographic models to include other atypical, non-standardized characteristics of mood disorders. However, regardless of the efforts made so far, a gap in classification still remains, putting restrictions in the clinical and neurobiological range of activities.