Setting aside the (deplorable) ethics and direct psychological impacts, have 20th century eugenics programs ever had an impact on the health of populations as a whole, beneficial or otherwise?
It's not really possible to know. These programs were not scientifically rigorous or adequately controlled, and the sheer number of factors that may or may not impact how individual people or entire societies develop means that it cannot be said with any degree of confidence whether or not eugenics programs worked.