For mental clarity and blood flow to the brain pick up Gingko Bilboa. It's the best vitamin out there for mental clarity. The B vitamins and Biotin help with stress, anxiety and as the previous poster noted regulating sleep. There are several B vitamins to choose from. I take just about all of them. If you have sleep problems pick up some Valerian Root. Don't get involved with Meletonin. That stuff will knock your socks off and the next day you won't know your ass from a hole in the ground. The Valerian Root is very subtle and puts you into a deep sleep, you'll have killer dreams on this stuff. And the next day you don't feel groggy.