Yes—lower blood levels were linked to more depression after birth in a study of 326 women. Researchers measured Vitamin D (25-OH) 24–48 hours after delivery. They checked for depression within six weeks after birth. Overall, 23.31% of the women had depression during that period. Women with depression had lower blood levels and higher depression questionnaire scores. Each 1 ng/mL higher blood level was linked to 25% lower odds of depression. That describes a link between women’s results. It does not prove that raising someone’s level would prevent depression. The researchers also tested how well the blood test could flag depression. Their best dividing point was 24.26 ng/mL. It correctly flagged 67.11% of women with depression. It correctly identified 85.20% of women without it. That means the test missed some cases and falsely flagged others. This dividing point is not a proven target for preventing depression. Sunlight and Vitamin D Supplementation were also linked to lower risk. Having a planned pregnancy was linked to lower risk, too. First-time mothers had higher risk. These findings show that blood levels were only one part of the picture. For BioSocial members, test timing matters when comparing notes. These results came from blood drawn shortly after birth, not months earlier. Recording the test date alongside mood changes and habits could make shared experiences easier to understand. Community notes can help reveal patterns without assuming one number explains someone’s experience. If you tracked your blood levels around pregnancy or after birth, what did you notice alongside your mood?