There are many causes of the ‘topped shot’ but many are caused by ‘Pre shot nerves’ or the desire to help the ball in the air. Both can be corrected by the golfer with some proper set up and mental corrections.
Many golfers are taught and over stress about ‘keeping their head down’, most of those bury their chin to low and their head is in the way of a proper shoulder turn, thus causing more issues. I have found very few golfers who’s head actually comes up in the swing, but I have found many golfers who bury their chin to low and their chest comes up which is a result of the chin down and that drives their whole body upward. Chin up is a much better thought then ‘head down’.
I use a lot of visionary drills to teach golfers what really gets the ball up in the air i.e. – hitting down and through ball, backspin vs top spin and many of these students quickly learn that their issues are more of a misinterpreted idea of what actually gets the ball into the air.