There have been few studies of whether vitamin D insufficiency is linked with depression in healthy young women despite women's high rates of both problems. Female undergraduates (n=185) living in the Pacific Northwest during fall, winter, and spring academic terms completed the Center for Epidemiologic Studies Depression (CES-D) scale weekly for 4 weeks (W1-W5). We measured serum levels of vitamin D-3 and C (ascorbate; as a control variable) in blood samples collected at W1 and W5. Vitamin D insufficiency (= 16) were 34-42% at W1-W5. Lower W1 vitamin D-3 predicted clinically significant depressive symptoms across WI-W5 (beta= -0.20, p <0.05), controlling for season, BMI, race/ethnicity, diet, exercise, and time outside. There was some evidence that lower levels of depressive symptoms in Fall participants (vs. Winter and Spring) were explained by their higher levels of vitamin D-3. W1 depressive symptoms did not predict change in vitamin D3 levels from W1 to W5. Findings are consistent with a temporal association between low levels of vitamin D and clinically meaningful depressive symptoms. The preventive value of supplementation should be tested further. (C) 2015 Elsevier Ireland Ltd. All rights reserved.