What's better to take regular nicain or nacinamide for depression and anxiety?

Neither: Niacin becomes converted to niacinamide in your body if there is a sufficient amount. Known as vitamin b-3, its deficiency can cause certain skin diseases, and it its use is helpful (only niacin) in reducing cholesterol. It is not shown in any evidence based study to have a positive effect upon depression or anxiety. If one eats enough green leafy vegetables it should provide enough natural b-3.