British Journal of Psychiatry (1995)

January 1, 1995

Y. Meesters, J.H.C. Jansen, D.G.M. Beersma, A.L. Bouhuys and R.H. Van Den Hoofdakker

British Journal of Psychiatry (1995), 166, 607-612


Background. Sixty-eight patients with seasonal affective disorder participated in a 10000-lux light treatment study in which two questions were addressed: do response rates differ when the light is applied at different times of the day and does short-term rank ordering of morning and evening light influence response rates?

Method. Three groups of patients received a 4-day light treatment: (I) in the morning (8.00-8.30 a.m., n=14), (II) in the afternoon (1.00-1.30 p.m., n=15) or (III) in the evening (8.00-8.30 p.m., n=12). Two additional groups of patients received two days of morning light treatments followed by two days of evening light (IV, n=13), or vice versa (V, n=14).

Results. Response rates for groups I, II and III were 69, 57 and 80% respectively, with no significant differences between them. Response rates for groups IV and V were 67 and 50% respectively; this difference was not significant and these percentages did not differ significantly from those of groups I and III.

Conclusions. The results indicate that the timing of light treatment is not critical and that short-term rank ordering of morning and evening light does not influence therapeutic outcome.