CIRCADIAN REST-ACTIVITY DISTURBANCES IN CHILDREN WITH SEASONAL AFFECTIVE-DISORDER

Objective: Seasonal affective disorder (SAD) affects from 1.7% to 5.5% of children. Previous studies found that nonseasonally depressed chil dren had a blunted circadian rhythm, white adults with SAD had a delay ed and poorly entrained rhythm. The purpose of this study was to deter mine whether pediatric SAD more closely resembles nonseasonal pediatri c depression or adult SAD. Method: Twelve normal, healthy volunteers ( 11.6 +/-: 3.7 years; 6 female, 6 male) and 14 unmedicated children wit h SAD (11.0 +/- 3.3 years; 9 female, 5 male) meeting Rosenthal/NIMH cr iteria for SAD and Schedule for Affective Disorders and Schizophrenia for School-Age Children-Epidemiologic version criteria for major depre ssion had their levels of activity recorded for 72 hours (weekdays) us ing belt-worn actigraphs. Results: The SAD group had blunted circadian amplitudes that were 10% lower than normal (p=.004). They were more p oorly modeled by the standard cosinor equation (p=.001), and a circadi an rhythm accounted for 39% less of the variability in their activity profile (p=.007). The amplitude of the 12-hour harmonic rhythm was mar kedly increased. There were no differences between SAD and control chi ldren in the timing of the circadian rhythm and degree of entrainment. Conclusions: Children with SAD displayed dysregulated circadian activ ity rhythms comparable with those reported in nonseasonally depressed children, yet different from those observed in adults.