Figure 2. Effect of Vitamin D3 or Omega-3s, Compared to Their Matching Placebos, on Risk of DSM-IV Incident MDD at 2 Years by Risk Group of Indicated and Selective Prevention^a.

^aFrom a total 720 eligible participants, 662 completed follow-up at year 2. For the coprimary outcome of incident MDD, P < .025 was considered as threshold for overall statistical significance.

^bRelative risk and its CI were based on exact tests using the exact χ² score statistic.

^cIndicated prevention targeted participants with subthreshold depression, but who did not meet DSM-IV criteria for current major depressive disorders or dysthymia, at baseline.

^dSelective prevention targeted participants with ≥ 1 high-risk factor for late-life depression at baseline; see details in Supplementary Appendix 1 (under E. Approach for selective prevention).

^eP-interaction was calculated using the Zelen exact test for equal odds ratios. The Zelen exact test was performed to determine whether effects of vitamin D₃ or omega-3s, compared to placebo, differ across risk groups of indicated and selective prevention.