 However, no randomized controlled treatment trial of RBD has been conducted.Disorders characterized by periods with depressive episodes lasting hours to days have been described since 1852 and have been labelled "periodic melancholia", "intermittent depressive disorder" or "very brief depression".The third version of the Diagnostic and Statistical Manual of Mental Disorders (1980), which relied heavily on findings from studies conducted in psychiatric in- and out-patient settings, required at least 14 days duration for a diagnosis of depression.