A chronic and debilitating condition, H.P.P.D. warps the perceptual faculties: the external senses are marred by a constellation of mostly visual distortions, while the internal ones are paralyzed by a concoction of dissociative symptoms, panic attacks, and depression. The doors of perception are not so much cleansed, as Aldous Huxley famously found after his first experience on mescaline, as they are cracked open and left askew. H.P.P.D. does not generate hallucinations, technically speaking. Sufferers can appreciate that their perceptual aberrations are unreal that their surroundings only appear blurred by afterimages and trails; shimmered by sparkles and flashed by bright bolts of light; interrupted by transparent blobs of color floating around; electrified by visual snow; magnified or shrunk by “Alice-in-Wonderland” symptoms; adorned by halos around objects, around people’s heads. The pseudo-hallucinations are ultimately unconvincing, if deeply unsettling. Eventually, a sense of permanent unreality casts a pall over the acid-fuelled dreamscape, and sufferers disassociate—from the world, due to derealization, and from themselves, due to depersonalization. At a recent Society of Biological Psychiatry conference, Dr. Abraham presented findings, later published in the S.B.P. 2012 supplement, that suggest up to sixty-five per cent of H.P.P.D patients chronically endure panic attacks, and fifty per cent, major depression. Some patients feel their only relief is suicide.

http://www.newyorker.com/tech/elements/a-trip-that-doesnt-end