Are the ICD-10 or DSM-5 diagnostic systems able to define those who will benefit from treatment for depression?

Two widely used diagnostic systems, the International Statistical Classification of Diseases and Related Health Problems (ICD-10) and the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), are reviewed for their ability to define those who will benefit from active treatment rather than placebo. Both systems suffer from a weakness in defining symptoms sufficiently clearly to separate depression from normal mood variations in the general population. Consequently, normal individuals may be medicalized and defined as suffering from and treated for depression. Also, in mild depression, unlike moderate depression, a lack of significant separation of active treatment from placebo has been shown in individual double-blind, placebo-controlled studies and in meta-analyses of these treatment studies. Both systems would be more useful for treatment purposes if they provided a clearer symptomatic definition of moderate depression, as is widely used in pivotal regulatory standard efficacy studies.