I have seasonal affective disorder and was taking a medication that sort of helped, but was causing mood swings if taken even slightly out of rhythm, increased my blood pressure, and was just generally not that effective, but it was better than nothing. Last winter I switched to vitamin D (it was already uncovered in blood tests I had a deficiency, which is what turned me onto it - when I started taking it, I felt a lot better) and omega 3 and I won't go back. I wish someone had told me a decade ago, probably would have saved a lot of damage to my organs (another reason I got off of it)