Better mental health
I don't believe studies have followed people for as long as 40 years but studies have generally found that the vast majority of those who used lsd
many years ago ascribe a variety of long-term mental health benefits to their experiences- greater self-awareness, happiness, inner peace etc.
Of course, some have had negative experiences as well. See http://www.Ukcia.Org/research/cunion/cu52.Htm.