Source, in full
As quoted in Wisdom for the Soul : Five Millennia of Prescriptions for Spiritual Healing (2006) by Larry Chang, p. 412; this might be a paraphrase, as the earliest occurrence of this phrase thus far located is in the form: "Ronald David Laing has shocked many people when he suggested in 1972 that insanity can be a perfectly rational adjustment to an insane world." in Studii de literatură română și comparată (1984), by The Faculty of Philology-History at Universitatea din Timișoara. A clear citation to Laing's own work has not yet been found.