You know that the so-called sunshine vitamin is integral for maintaining strong bones and that it plays an important role in metabolism. It is a precursor to many hormones and is integral in the proper functioning of your heart, lungs, and muscles. Doctors and researchers are still working to understand the other ways vitamin D effects the body. While it has long been suspected that vitamin D also plays a role in the cognition and mood, clinical evidence to confirm this hypothesis was scarce. Now, mounting evidence suggests that vitamin D levels may be linked to depression.