Validity of seasonal pattern as a modifier for recurrent mood disorders for DSM-IV.

Data are reviewed regarding the validity of seasonal pattern (SP), according to DSM-III-R, as a modifier for recurrent mood disorders. The relationship of the DSM-III-R formulation of SP is compared with that of seasonal affective disorder (SAD) as used by the bulk of researchers in the area. Both definitions are evaluated against the criteria for validity suggested by Robins and Guze, by Kendell, and by Spitzer and Williams. While the two definitions are similar and available data support a distinct clinical syndrome of recurrent winter decrements of mood and energy, it is not yet clear whether what is identified as SP or SAD represents a distinct affective syndrome, a subtype of recurrent affective illness, or the most severe form of a widely distributed population trait. Several options for operationalized criteria sets are discussed.