Their youngsters are often freshman or sophomores struggling to adjust to their new lives. Some are lonely or depressed. Others seem to be developing eating disorders or are drinking or partying too much. Some have been hospitalized for alcohol poisoning. The parents are seeking professional guidance because, even though every instinct says they should take some sort of action, they are afraid that doing so will be bad for their almost adult child's emotional health. Most of the advice they get from friends, books and the internet tells them to let their youngsters figure things out for themselves.
These clients don't want to be overprotective, hovering "helicopter" parents who cannot let go appropriately. They are seriously concerned, but they think that maybe their anxiety is neurotic. The received wisdom of our culture is that when an adolescent reaches the age of 18 he is supposed to be on his own.(See this NY Times article.) His parents are no longer supposed to offer advice (which he most likely won't take anyway).