DSM-IV (Direct Quote) A) The reexperiencing, following cessation of use of a hallucinogen, of one or more of the perceptual symptoms that were experienced while intoxicated with the hallucinogen (e.g., geometric hallucinations, false perceptions of movement in the peripheral visual fields, flashes of color, intensified colors, trails of images of moving objects, positive after-images, halos around objects, macropsia and micropsia)." B) The symptoms in Criterion A cause clinically significant distress or impairment in social, occupational, or other important areas of functioning. C)The symptoms are not due to a general medical condition (e.g., anatomical lesions and infections of the brain, visual epilepsies) and are not better accounted from by other mental disorders (e.g., delirium, dementia, Schizophrenia) or hypnopompic hallucinations.