Mood disorders: review of current diagnostic systems

In their sections on mood disorders, both ICD-10 and DSM-IV represent considerable advances on ICD-9 in drawing affective disorders together in one section, distinguishing bipolar disorder from unipolar, including dysthymia and using clear definitions. Problems with ICD-10 include complexity, use of different clinical and research definitions, emphasis on single versus recurrent episodes and the lack of some clinically useful subtypes. DSM-IV is less complex but assigns separate unjustified categories of medical and substance-induced mood disorders, and fails to code its useful qualifiers. Both classifications preserve categories for psychotic depression and melancholia/somatic syndrome, which are better coded in ICD-10. The severity distinctions could usefully be extended to a milder category of minor depression. It is also recommended that the two classifications be brought together, with small differences in definitions ironed out and a single set used both clinically and for research, the simpler DSM-IV organisation, the omission of the categorisations of single versus recurrent and mood disorder due to general medical or substance abuse disorders, and the inclusion of coding for some subtypes such as seasonal and postpartum.