The Social Rhythm Metric (SRM): measuring daily social rhythms over 12 weeks.

A "Social Rhythm Metric" (SRM) of daily rhythmic behavior (developed previously) was given to 20 treated depressives (in remission) and 15 day-working control subjects for a continuous 12-week period. Long-term use of the SRM appeared feasible with no evidence of a deterioration in scores over the 12 weeks. Comparisons were made between intersubject and intrasubject variability, as well as a study of overall trends in SRM during the 12 weeks. Two further measures from the instrument--the Activity Level Index (ALI) and Other Person Involvement--were developed and shown to be useful adjuncts to the SRM. Although no simple differences in absolute SRM score emerged between patients and controls, there were significant differences in intersubject vs. intrasubject variability between the two groups. The patients showed more intrasubject variability and required more weeks of sampling to achieve a stable "trait" measure. Patients' social rhythms also appeared to be more "other person" prompted than those of controls.