Figure 8.Percent change in (SIGH-SAD) depression score after correct treatment incorrect treatment and placebo, as well as incorrect treatment and placebo combined (correct treatment such as giving PM melatonin to phase-delay SAD patients, etc; see text for details of the composition of these treatment groups). Baseline SIGH-SAD scores for the three treatment groups (correct treatment incorrect treatment and placebo) were 28.9+1.0, 28.8+1.3, and 26.6+1.4, respectively. The Kruskal-WallisHtest (χ^{2}=5.83, *df=2,* *P=0.05)* was statistically significant, but not the one-way ANOVA (F =2.96 on [2, 65], P=0.06). By using the Welch two-sample f test to compare differences in the change scores of the correct-treatment group with those of the other groups, correct treatment significantly decreased depression ratings more than the other groups: incorrect (19.1%: *t* =2.09, *df* =40.8, *P* =0.04); placebo (20.9%: *t=2.* 60, *df* =34.2, P=0.01); the latter two groups combined (19.9%: t=2.65, *df* *=32.1,* P=0.01). Pretreatment to post-treatment percent changes were significant for all groups: correct *(t* =5.43, *df* = 16, P<0.001), incorrect (f =2.20, *df* =26, P=0.04), placebo (t=2.50, df =23, P=0.02), and the latter two groups combined *(t* =3.25, *df* =50, *P* =0.002). Effect sizes (ES) are shown for pretreatment to posttreatment percent change scores for each group; also shown are the more conservative ES for differences in change scores between the correct treatment group and the other groups. (Before phase typing, percent change in the pm treated group was -28.5 + 5.6, and percent change in the am treated group was -15.5 + 8.0, although there were no statistically significant differences between the three treatment groups in percent changes in SIGH-SAD scores [see above]). SAD, seasonal affective disorder Adapted from ref 20: Lewy AJ, Lefler BJ, Emens JS, Bauer VK. The circadian basis of winter depression. *Proc Natl Acad Sci U S A.* 2006:103:74147419. Copyright © National Academy of Sciences 2006.

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