While many recent studies have concluded that psilocybin can occasion mystical-type experiences having substantial and sustained personal meaning and spiritual significance, not all the medical community is on board. Paul R. McHugh, formerly director of the Department of Psychiatry and Behavioral Science at Johns Hopkins, responded as follows in a book review: "The unmentioned fact in "The Harvard Psychedelic Club" is that LSD, psilocybin, mescaline, and the like produce not a "higher consciousness" but rather a particular kind of "lower consciousness" known well to psychiatrists and neurologists—namely, "toxic delirium."" In response to Dr. McHugh's denial that the mystical experience leads to insight, Michael Pollan points to Roland Griffiths, Johns Hopkins researcher and author of many studies finding that the experiences of many of the participants have actually involved substantial and sustained personal meaning bringing enduring positive changes in psychological functioning. According to Pollan, Griffiths admits that those taking psilocybin may be encountering a temporary psychosis, but notes that the patients McHugh describes are unlikely to report years later of their experience: "Wow, that was one of the greatest and most meaningful experiences of my life". Such responses argue that it is not appropriate to automatically equate a psilocybin-induced experience of profound insight with superficially similar experiences of psychiatric patients (characterized as mere toxic delirium), when it is only the "insight" reached in the psilocybin experience that is reported to often result in profound, beneficial and enduring life changes for the person.