It's a bit different from both DA:O and DA2, actually.
In DA:O, you got attribute points to distribute, but the dependant statistics also rose by level. So you got more HP even if you didn't put points into Constitution.
In DA2, you got points to distribute per level, but the dependant stats were only effected by putting points to stats. So you only got more HPs if you put points to Constitution.
In DA:I, you don't get points to distribute, but the dependant stats go up per level.
IIRC, this applied to all dependant stats in all games, but I might be wrong. Bottom line is, they're all a bit different.