The VITamin D and OmegA-3 TriaL (VITAL; NCT 01169259) is an ongoing randomized clinical trial in 25,871 U.S. men and women investigating whether taking daily dietary supplements of vitamin D3 (2000 IU) or omega-3 fatty acids (Omacor® fish oil, 1 gram) reduces the risk of developing cancer, heart disease, and stroke in people who do not have a prior history of these illnesses. This ancillary study is being conducted among participants in VITAL and will examine whether vitamin D or fish oil: 1) reduces risk of clinical depressive syndrome, 2) yields better mood scores over time, compared to placebo.

VITAL-DEP: Depression Endpoint Prevention in the VITamin D and OmegA-3 TriaL is a randomized clinical trial of vitamin D (in the form of vitamin D3 [cholecalciferol]) and marine omega-3 fatty acid (eicosapentaenoic acid [EPA] + docosahexaenoic acid [DHA]) supplements in the prevention of depression in older adults. Existing data from laboratory studies, epidemiologic research, limited clinical trials research suggest that these nutritional agents may reduce risk of depression or improve mood, but large primary prevention trials with adequate dosing and lengthy treatment durations in general populations are lacking.

Eligible participants will be assigned by chance (like a coin toss) to one of four groups: (1) daily vitamin D3 and omega-3; (2) daily vitamin D3 and omega-3 placebo; (3) daily vitamin D placebo and omega-3; or (4) daily vitamin D placebo and omega-3 placebo. Participants have an equal chance of being assigned to any of these four groups and a 3 out of 4 chance of getting at least one active agent.

Participants in all groups will take two pills each day -- one softgel that contains either vitamin D3 or vitamin D placebo and one capsule that contains either omega-3 or omega-3 placebo. Participants will receive their study pills in convenient calendar packages via U.S. mail.

Participants will also fill out a short (15-20 minute) questionnaire each year. The questionnaire asks about health; lifestyle habits such as physical exercise, diet, and smoking; use of medications and dietary supplements; family history of illness, and new medical diagnoses. The questionnaire also includes specific questions pertaining to mood. Occasionally, participants may receive a phone call from study staff to collect information or to clarify responses on the questionnaire.

Primary aims of 1) reduction in risk of clinical depressive syndrome and 2) yielding of better mood scores over time will be address in the full VITAL cohort of 20,000. Secondary aims will be addressed in sub-set of participants. The secondary aims will address whether: 1) among a subset of 1,000 participants evaluated at a Clinical and Translational Science Center (CTSC), the agents reduce risk of depression and yield better mood scores among persons with known risk factors for late-life depression; 2) among a subset of 1,000 participants evaluated at a CTSC, the agents reduce risk of major depression and yield better mood scores among persons with sub-syndromal depressive symptoms; 3) among all VITAL participants, African-American race (African-Americans have high risk of Vitamin D deficiency) modifies effects of vitamin D3 supplementation on late-life depression risk and on mood scores; 4) among a subset of participants, baseline plasma levels of vitamin D and omega-3 fatty acids are related to depression risk and/or modify agent effects.

Thus, VITAL-DEP will address simultaneously the impact of both vitamin D and fish oil for universal, selective and indicated prevention of late-life depression.

Participants in VITAL (NCT 01169259) who meet the following criteria are eligible to participate in this ancillary study. These are the criteria specific for testing of the primary aims in the VITAL-DEP ancillary study:

• no current significant depressive symptoms
• no core major depressive disorder symptoms for a period of two or more weeks in the past two years
• no history of alcohol and/or substance abuse disorder active in the past 12 months, schizophrenia or other primary psychotic disorder, bipolar disorder, post-traumatic stress disorder or obsessive-compulsive disorder
• no current psychotherapy or current use of psychotropics (including non-prescription agents for the treatment of mood disorders), except for limited use of mild sedatives/hypnotics
• no history of major neurologic disorder or delirium episode in the past 12 months
• no history of clinical (i.e., overt and not sub-clinical) hypothyroidism diagnosis

Adverse event data were collected over the entire randomized treatment and follow-up period, which was a median of 5.3 years. VITAL-DEP is an ancillary study of the VITAL trial. For total adverse events reported by the parent VITAL trial, please see Results reported by VITAL, NCT01169259.

Results for adverse events are reported by each of the 4 factorial arms of the trial.