The spectrum concept of mental disorders means that a series of diseases consists of several subtypes, each of which overlap in their symptoms or etiologies. One of the most accepted spectrum concepts is a "bipolar spectrum". The bipolar spectrum concept has clinical validity of the diagnosis and treatment of the patients with bipolarity features in their course and symptoms. However, this concept may confuse categorical distinctions of mood disorders and lead over-diagnose of bipolar disorders. The over-diagnosis of bipolar spectrum may cause over-prescription of mood stabilizers. The medicalization of "normal mood swing" might also occur. In these years, several anticonvulsants and second generation antipsychotics acquired a new indication as a "mood stabilizer". If the marketing of mood stabilizer is hidden behind the expansion of bipolar spectrum, clinicians should assess the clinical validity of this concept more carefully.