Talk:Hallucinogen persisting perception disorder

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[edit] Flashbacks

I have added the expert required tag. We are rewriting and clarifying the information in this article. It will include significantly more references to research, private communications with researchers in the area, current research that is being created, and clarification of terms and information used in the article. This should take 3-5 days. NODID 15:48, 5 September 2007 (UTC)

I think I'm just going to remove the " often reffered to as flashbacks" because there is a distinct difference, HPPD constant, it's damaged vision, flashbacks are just vivid memory of being on the whatever hallucinogen was taken.

Here is pretty good page that covers that fact: http://www.erowid.org/psychoactives/health/hppd/hppd_faq.shtml#flashback Iameatingjam 00:27, 28 April 2007 (UTC)

Great work for the user adding information on other possible explanations for HPPD, such as neurodegenerative disorders.NODID 13:27, 19 June 2007 (UTC)

[edit] Cognitive

I'm interested in higher cognition, but my experiences with HPPD make me want to know more about the mechanism involved with simple persistent perceptual distortions, e.g., "trails." I conjecture that HPPD is analogous to having learned to discriminate the morphemes of a foreign language. The effect is persistent because a percept's constituent sensations are "repacked" as a new (often salient) percept which is experienced and memorized. As learning a new language can degrade the cradle tongue temporarily and superficially, so HPPD can interfere with environmentally adapted perception. But these effects can be overcome in time by re-training the discriminations that created these categories of perception in the first place. In practice, this means concentrating on adaptive perceptions and ignoring any unwanted hallucinatory perceptions. Long periods of disuse will reduce HPPD hallucinations, until eventually, they should become difficult or even impossible to produce.

I have never heard of anyone being disabled because of HPPD per se, although HPPD can be unsettling if severe, or worrisome if the sufferer believes he or she has become permanently deranged. Although hallucinations are maladaptive in the natural environment, I wonder if there may be some benefit from controlled altered perception to global functioning, e.g., in adaptability, imagination, etc.

Concerning the discussion of Depersonalization disorder below, it seems, if true, that this transient and superficial dissociation ties in with self-awareness as a perception or perhaps a sensation, in this case slightly blocked, distorted or misplaced.

70.95.168.25 10:44, 14 January 2007 (UTC)

[edit] Research

It would be interesting to see some unbiased research into this topic. Dr. Henry Abraham has done some initial research, but his obvious bias may taint his research. For instance are people who are prone to perceptual distortions and weak colour discrimination drawn to hallucinogenic drugs? Do they naturally have a different flicker threshold and persistence of vision?

How many people experience visual changes? What about other senses? How many users actually consider this a positive change?

This isn't necessarily always or even mostly a negative change.

Reply. As a self-diagnosed sufferer of HPPD I find it pretty harmless but overall annoying. before it had started i had smoked cannabis daily for over a year and had taken magic mushrooms, salvia and ecstacy several times. Whenever I concentrate on an object it usually seems to move around a few inches and whenever I am in a dark room, or close my eyes, I see mind blowing patterns all over the wall. A friend of similar age (17) has these too, they are usually spinning abstract shapes that collide into each other and form another, bigger shape that in turn spins and splits etc. etc. My friend and I do not find these threatening any more, as we know they are not real and a probably result of drug abuse, instead they make night time lying in bed a lot more interesting. It should probably be mentioned that my friend has only ever has salvia and cannabis, perhaps hinting at a relationship between salvia and this disorder? The other senses seem to be normal and perception of colour is always spot on with him, but they do blur after a while for me.

Well I am guessing salvia has a relationship to this disorder considering the name of it is Hallucinogen Persisting Perception Disorder, and Salvia is a hallucinogen. I disagree and don't think any of this should be mentioned considering it hasn't been studied enough to find the amount of people and those questions are just unimportant. If you would like to seek these answers view the official message board that Dr. Heny Abraham monitors. hppdonline.com Dcs937

Reply. I'm new to wikipedia so I hope I"m following etiquitee properly. In response to the suggestion that Dr. Abraham's work is biased, could the problem instead be that the person who wrote the article innacurately represented Dr. Abraham's work. I think the author of this wiki paraphrased an article by Dr. Abraham and may have omitted the actual reasoning that Dr. Abraham gives of why he can draw his particular conclusion from that experiment. I'm thinking that Dr. Abraham had a hypothesis about hppd which would be proven if the flicker sensitivity of individuals with hppd was decreased which the author neglected to include. Really, why would Dr. Abraham chose this particular experiment Vigual?

A reason to study flicker sensitivity is that visual information is split into separate channels and one of the channels can detect faster changes than the other. By measuring perception of flicker you can separately test that one channel. With enough different tests, you can figure out the cause. There definately does need to be more research on HPPD to figure out what its causes are and how to best treat it. A group at the University of California @ Berkeley is collaborating with erowid.org to study HPPD in an unbiased fashion.

--67.101.147.33 (talk) 15:57, 9 May 2008 (UTC)

[edit] Flashbacks

This article needs some discussion of HPPD in the context of "flashbacks" of a psychedelic experience. I've heard HPPD described as a medical diagnosis of what is colloquially called a "flashback", but I've also heard of "flashbacks" covering a wider range of phenomena, and that HPPD is the most extreme manifestation of HPPD.

Also, this article is somewhat POV - the extent and seriousness of HPPD and "flashback" phenomena are questioned by many, and these questions should be addressed in this article. Peter G Werner 18:38, 5 April 2006 (UTC)

Agreed. The LSD article mentions several theories as to the causes of HPPD, only 1 of which is mentioned here. Adding the POV tag for now, until someone with more knowledge of the subject matter looks into it. Mzyxptlk 19:37, 8 December 2006 (UTC)

Disagreed. HPPD stands for Hallucinogen Persisting Perception Disorder. Flashbacks is a common misinterperit that doctors seem to think it is. Or simply just a term. Dcs937

First, my apology for the quick references to research contained below. It is unfortunate that the DSM-IV-TR contains the word "Flashback" as a subheading for the diagnosis of HPPD. (The criteria for a disorder to be "persisting" is being reviewed for the new version of the DSM-V). We are dealing with different experiences, and producing good quantitative data on a transient flashback is almost impossible. Individuals who experience these short experiences have neither the same symptom profile nor the same etiology of those individuals who experience HPPD in the chronic form. "Flashbacks" is a clinically useless term because of its misuse.^[1][2]

In my private communications with Dr. AG Lerner, Dr. John Halpern, and Dr. Henry David Abraham, it is universally agreed that the term "flashback", particularly when reviewing early literature, is useless because each researcher defined this term in different ways.^[3] The current theory for chronic HPPD, which proposes that the symptoms are at least partially caused from structural changes to GABAergic interneurons, which typically produce inhibitory responses; thsee inhibitory neurons have serotonergic inputs. Consequently, this inhibitory system does not produce the appropriate GABA output to the next system in the visual cortex. HPPD-like symptoms have been recreated using potent serotonin antagonists that target this system. I will add the appropriate literature on this topic on the main page. Although the seriousness of HPPD may be questioned by researchers unfamiliar with the wealth of literature on the topic, as the past Administrator/Creator of the HPPD message board mentioned above, and also as President of the National Organization for Drug-Induced Disorders, I know of individuals who were so overwhelmed by their symptoms that it has lead to suicide. I understand the skepticism about HPPD because there is not a dose-dependent relationship and individuals with chronic HPPD are rare, however I have had long discussions with researchers who initially felt that HPPD was not a real disorder, and I have been quite successful in demonstrating that at the very least, even if we do not draw a strict causal relationship between the drug use and the distressing symptoms of HPPD, they do believe that there are individuals who are suffering from severe visual perceptual problems and these individuals have a commonality: they all used hallucinogens and the symptoms are similar to the hallucinogen experience. Personally, I am not anti-drug, but I am pro-education. Many legal drugs cause unusual and even paradoxical reactions in rare populations of patients; this includes many drugs that are commonly prescribed and considered safe for use. The recent research using hallucinogens to manage Cluster Headaches is reasonable in my opinion, as I feel that these sufferers, who experience enormous levels of pain, deserve to have access to any relief that they are able to find. However, I do feel that the organization should exist in the event that a negative reaction does occur to these drugs.David Kozin 05:35, 6 January 2007 (UTC)

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 : : Since someone more knowledgeable (David) has looked into it, I am removing the POV tag. --Generalmiaow 21:56, 19 January 2007 (UTC)

[edit] Help needed

I would like to mention on this page that HPPD is very often comorbid with Depersonalisation Disorder which it is (a quick survey of dpselfhelp.com or hppdonline.com would show that about a third of HPPDers have Depersonalisation) However there is no serious academic article that says there is (apart from the forthcoming NODID study with has not been published yet). What should I do? Say that it's based on a web forum? There is so little about HPPD out there, but this is definitely true, just not backed up by research yet... Generalmiaow 23:28, 8 May 2006 (UTC)

Actually, quantitative evidence of differences between HPPD patients and control populations do exist, and I have pointed out two such studies in the main article. Additionally, I have added some ideas for future research to further examine HPPD in the chronic (24/7) form. There is a suggested etiology, and I would like to examine this in the next week with a much more scholarly and literature-backed review of this disorder. I would have to agree with Mr. Werner's criticism above and it was put kindly, which is to say that the current article is roughly focused on a POV, however it does not have to be. There are good reasons why HPPD has been a controversal subject for clinicians and some researchers. The biggest obsticles are that HPPD appears to have no known predictable onset, no dose-dependent:symptom-severity ratio, and is extremely rare when we consider the large quantity of hallucinogen users. However, just because these are not yet known does not equate to the disorder not existing, but does give us a challenge and by recognizing the skeptical views, we are able to present this with a much more honest view. I will create an improved version of this article this week. However, I am going to fix up a few misconceptions in the article today, and I previously added the Future Research Section.

Also, regarding our NODID study on characterizing drug-induced Depersonalisation Disorder, the timeline for the final manuscript to be complete is December, and then submission for peer-review and publication are in the final stages. This write-up for the research project is currently awaiting final completion of the manuscript from the Depersonalization and Dissociation Research Program. Information on this study will be published when it is complete.

I have added a link to the NODID web site on the main article, and in all honestly I am new to all of the rules/regulations of Wikipedia. I did not do this as shameless promotion, but it contains an extensive bibliography on the topic. --David Kozin 08:39, 26 October 2006 (UTC)

Update: "The research has been submitted for publication for review with the British Journal of Psychiatry. Essentially, our first paper is a factor analysis of different aspects of Depersonalization disorder based on the analysis of the Cambridge Depersonalization Scale. Depersonalisation encompasses underlying dimensions that have not been well defined, leading to clinical limitations in the diagnosis of depersonalisation disorder. The Cambridge Depersonalisation Scale was factor analyzed in 394 adults who endorsed depersonalization/derealisation via an internet survey. Five factors were extracted: emotional numbing, unreality of self, detachment from past, unreality of surroundings, and perceptual alterations. Results were similar to an earlier factor analysis in a smaller sample of 138 participants (Sierra et al, 2005). The findings strongly support the conceptualization of depersonalization as a multi-dimensional construct, and lend themselves to the formulation of more precise diagnostic criteria for depersonalisation disorder." (Currently this is copyright (c) 2007 by Simeon, D., Kozin, D. et al, until publication)David Kozin 05:47, 6 January 2007 (UTC)

I wanted to update the community that the publication discussed above is still in review, and it not yet published.NODID 13:28, 19 June 2007 (UTC)

Some references need to be added to the front page. Here is a comprehensive list:

Abraham, H.D., 1980. A chronic impairment of colour vision in users of LSD. Br. J. Psychiatry 140, 518—520.

Abraham, H.D., 1983. Visual phenomenology of the LSD flashback. Arch. Gen. Psychiatry 40, 884—889.

Abraham, H.D., 1984. LSD flashbacks (Letters to the Editor – In Reply). Arch. Gen. Psychiatry 41, 632.

Abraham, H.D., Aldridge, A.M., 1993. Adverse consequences of lysergic acid diethylamide. Addiction 88, 1327—1334.

Abraham, H.D., Duffy, F.H., 1996. Stable quantitative EEG difference in post-LSD visual disorder by split-half analysis: evidence for disinhibition. Psych. Res. Neuroimaging 67, 173—187.

Abraham, H.D., Duffy, F.H., 2001. EEG coherence in post-LSD visual hallucinations. Psych. Res. Neuroimaging 107, 151—163.

Abraham, H.D., Mamen, A., 1996. LSD-like panic from risperidone in post-LSD visual disorder. J. Clin. Psychopharmacol. 16, 228—231.

Abraham, H.D., Wolf, E., 1988. Visual function in past users of LSD: psychophysical findings. J. Abnorm. Psychol. 97, 443—447.

Abraham, H.D., Aldridge, A.M., Gogia, P., 1996. The psychopharmacology of hallucinogens. Neuropsychopharmacology 14, 286—298.

Alarcon, R.D., Dickinson, W.A., Dohn, H.H., 1982. Flashback phenomena: clinical and diagnostic dilemmas. J. Nerv. Ment. Dis. 170, 217—223.

Aldurra, G., Crayton, J.W., 2001. Improvement of hallucinogen persisting perception disorder by treatment with a combination of fluoxetine and olanzapine: case report. J. Clin. Psychopharmacol. 2, 343—344.

American Psychiatric Association, 1994. Diagnostic and Statistical Manual of Mental Disorders, IV. American Psychiatric Press, Inc., Washington, D.C.

Anderson, W., O’Malley, J., 1972. Trifluoperazine for the trailing phenomenon. J. Am. Med. Assoc. 220, 1244—1245.

Annis, N.M., Smart, R.G., 1973. Adverse reactions and recurrence from marijuana use. Br. J. Addict. 68, 315—319.

Apter, J.T., Pfeiffer, C.C., 1957. The effect of the hallucinogenic drugs LSD-25 and mescaline on the electroretinogram. Ann. N.Y. Acad. Sci. 66, 508—514.

Barron, S.P., Lowinger, P., Ebner, E., 1970. A clinical examination of chronic LSD use in the community. Compr. Psychiatry 11, 69—79.

Batzer, W., Ditzler, T., Brown, C., 1999. LSD use and flashbacks in alcoholic patients. J. Addict. Dis. 18, 57—63.

Blumenfield, M., 1971. Flashback phenomena in basic trainees who enter the US Air Force. Mil. Med. 136, 39—41.

Cohen, S., 1960. Lysergic acid diethylamide: side effects and complications. J. Nerv. Ment. Dis. 130, 30—40.

Cohen, S., 1966. A classification of LSD complications. Psychosomatics VII, 182—186.

Cohen, S., Ditman, K.S., 1963. Prolonged adverse reactions to lysergic acid diethylamide. Arch. Gen. Psychiatry 8, 475—480.

Cooper, H.A., 1955. Hallucinogenic drugs. Lancet 268, 1078.

Creighton, F.J., Black, D.L., Hyde, C.E., 1991. ‘Ecstasy’ psychosis and flashbacks. Br. J. Psychiatry 159, 713—715.

Denson, R., 1967. Dissociative delirium after treatment with lysergide. CMAJ 97, 1222—1224.

Ellis, H., 1898. Mescal: a new artificial paradise. Contemporary Review 73:130—141 (reprinted in The Smithsonian Institution Annual Report 1898, pp. 537—548).

Favazza, A.R., Domino, E.F., 1969. Recurrent LSD experience (flashbacks) triggered by marijuana. Univ. Mich. Med. Cent. J. 35, 214—216.

Fischer, R., 1971. The ‘flashback’: arousal-statebound recall of experience. J. Psychedelic Drugs 3, 31—39.

Fischer, R., 1977. On flashback and hypnotic recall. Int. J. Clin. Exp. Hypn. XXV, 217—235.

Fischer, R., Hill, R.M., Worshay, D., 1969. Effects of the psychedysleptic drug psilocybin on visual persception. Experientia 25, 166— 167.

Frosch, W.A., Robbins, E.S., Stern, M., 1965. Untoward reactions to lysergic acid diethylamide (LSD) resulting in hospitalization. N. Engl. J. Med. 273, 1235—1239.

Gastaut, H., Ferrer, S., Castells, C., 1953. Action de la die´thylamide de l’acide d-lysergique (LSD-25) sur les functions psychiques et l’e´lectroence´phalogramme. Confina Neurol. 13, 102—120.

Genova, P., 2000. The Thaw: 24 Essays in Psychotherapy. Dorrance Publishing, Pittsburgh, pp. 17—19.

Halpern, J.H., Pope, H.G., Jr, Sherwood, A., Hudson, J.I., Yurgelun- Todd, D., 2001. Neuropsychological effects of long-term hallucinogen use in Native Americans (abstract). Drug Alcohol Depend. 63 (S1), S62.

Harley-Mason, J., Laird, A.H., Smythies, J.R., 1958. The metabolism of mescaline in the human. Confina Neurol. 18, 152—155.

Heaton, H.K., 1975. Subject expectancy and environmental factors as determinants of psychedelic flashback experiences. J. Nerv. Ment.

J.H. Halpern, H.G. Pope, Jr / Drug and Alcohol Dependence 69 (2003) 109—119 117

Heaton, H.K., Victor, R.G., 1976. Personality characteristics associated with psychedelic flashbacks in natural and experimental settings. J. Abnorm. Psychol. 85, 83—90.

Hemsley, D.R., Ward, E.S., 1985. Individual differences in reaction to the abuse of LSD. Person. Individ. Diff. 6, 515—517.

Holiday, A.R., Hall, F.M., Sharpley, R.P., 1965. The effects of lysergic acid diethylamide: 1. Critical flicker frequency. Proc. West. Pharmacol. Soc. 8, 48—50.

Holsten, F., 1976. Flashbacks: a personal follow-up. Arch. Psychiatr. Nervenkr. 222, 293—304.

Horowitz, M., 1969. Flashbacks: recurrent intrusive images after the use of LSD. Am. J. Psychiatry 126, 565—569.

Juve, J.L., 1972. Bad drug trips and flashbacks. Child Welfare LI, 41— 50.

Kawasaki, A., Purvin, V., 1996. Persistant palinopsia following ingestion of lysergic acid diethylamide (LSD). Arch. Ophthalmol. 114, 47—50.

Keeler, M.H., 1967. Adverse reaction to marijuana. Am. J. Psychiatry 124, 674—677.

Keeler, M.H., Reifler, C.B., Liptzin, M.D., 1968. Spontaneous recurrence of marijuana effect. Am. J. Psychiatry 125, 384—386.

Kleber, H.D., 1967. Prolonged adverse reactions from unsupervised use of hallucinogenic drugs. J. Nerv. Ment. Dis. 144, 308—319.

Krill, A.E., Wieland, A.M., Ostfield, A.M., 1960. The effect of two hallucinogenic agents on human retinal function. Arch. Ophthalmol. 64, 724—733.

Landis, C., Clausen, J., 1954. Certain effects on mescaline and lysergic acid on psychological functions. J. Psychol. 38, 211—221.

Lerner, A.G., Oyffe, I., Issacs, G., Mircea, M., 1997. Naltrexone treatment of hallucinogen persisting perception disorder. Am. J. Psychiatry 154, 437.

Lerner, A.G., Finkel, B., Oyffe, I., Merenzon, I., Sigal, M., 1998. Clonidine treatment for hallucinogen persisting perception disorder. Am. J. Psychiatry. 155, 1460.

Lerner, A.G., Gelkopf, M., Oyffe, I., Finkel, B., Katz, S., Sigal, M., Weizman, A., 2000. LSD-induced hallucinogen persisting perception disorder treatment with clonidine: an open pilot study. Int. Clin. Psychopharmacol. 15, 35—37.

Lerner, A.G., Skladman, I., Kodesh, A., Sigal, M., Shufman, E., 2001. LSD-induced hallucinogen persisting perception disorder treatedwith clonazepam: two case reports. Isr. J. Psychiatry Relat. Sci. 38, 133—136.

Lowry, J.V., 1969. Mental health services for misusers of drugs in California. Ca. Ment. Health Res. Digest 7, 99—107.

Markel, H., Lee, A., Holmes, R.D., Domino, E.F., 1994. LSD flashback syndrome exacerbated by selective serotonin reuptake inhibitor antidepressants in adolescents. J. Pediatr. 125, 817—819.

Matefy, R.E., 1973. Behavior therapy to extinguish spontaneous recurrences of LSD effects: a case study. J. Nerv. Ment. Dis. 156, 226—231.

Matefy, R.E., 1980. Role-play theory of psychedelic drug flashbacks. J. Consult. Clin. Psychol. 48, 551—553.

Matefy, R.E., Krall, R.G., 1974. An initial investigation of thepsychedelic drug flashback phenomena. J. Consult. Clin. Psychol. 42, 854—860.

Matefy, R.E., Hayes, C., Hirsch, J., 1978. Psychedelic drug flashbacks: subjective reports and biographical data. Addict. Behav. 3, 165— 178. Matefy, R.E., Hayes, C., Hirsch, J., 1979. Psychedelic drug flashbacks: attentional deficits? J. Abnorm. Psychol. 88, 212—215.

McGee, R., 1984. Flashbacks and memory phenomena: a comment on ‘‘Flashback phenomena*/Clinical and diagnostic dilemmas’’. J.Nerv. Ment. Dis. 172, 273—278.

McGlothlin, W.H., Arnold, D.O., 1971. LSD revisited: a ten-year follow-up of medical LSD use. Arch. Gen. Psychiatry 24, 35—49. McGuire, P.K., Cope, H., Fahy, T.A., 1994. Diversity of sychopathology associated with use of 3,4-methylenedioxymethamphetamine.(‘Ecstasy’). Br. J. Psychiatry 165, 391—395.

Morehead, D.B., 1997. Exacerbation of hallucinogen-persisting perception disorder with risperidone. J. Clin. Psychopharmacol. 17, 327—328.

Moskowitz, D., 1971. Use of haloperidol to reduce LSD flashbacks. Mil. Med. 136, 754—756.

Naditch, M.P., 1974. Acute adverse reactions to psychoactive drugs, drug usage, and psychopathology. J. Abnorm. Psychol. 83, 394— 403.

Naditch, M.P., Fenwick, S., 1977. LSD flashbacks and ego functioning. J. Abnorm. Psychol. 86, 352—359.

Nichols, C.D., Sanders-Bush, E., 2002. A single dose of lysergic acid diethylamide influences gene expression patterns within the mammalian brain. Neuropsychopharmacology 26, 634—642.

Ostfeld, A.M., 1961. Effects of LSD 25 and JB 318 on tests of visual and perceptual functions in man. Fed. Proc. 20, 876—883.

Robbins, E., Frosch, W.A., Stern, M., 1967. Further observations on untoward reactions to LSD. Am. J. Psychiatry 124, 393—395.

Sadoff, R.L., 1973. LSD, alcohol, and homicide. J. Am. Med. Assoc. 225, 1123.

Saidel, D.R., Babineau, R., 1976. Prolonged LSD flashbacks as conversion reactions. J. Nerv. Ment. Dis. 163, 352—355.

Schwarz, C.J., 1968. The complications of LSD: a review of the literature. J. Nerv. Ment. Dis. 146, 174—186.

Shick, J.F.E., Smith, D.E., 1970. Analysis of the LSD flashback. J. Psychedelic Drugs 3, 13—19.

Smart, R., Bateman, K., 1967. Unfavourable reactions to LSD: a review and analysis of the available case reports. CMAJ 97, 1214— 1221.

Smith, D.E., 1968. The acute and chronic toxicity of marijuana. J. Psychedelic Drugs 2, 37—47.

Stanton, M.D., 1972. Drug use in Vietnam: a survey among army personnel in the two northen corps. Arch. Gen. Psychiatry 26, 279—286.

Stanton, M.D., Bardoni, A., 1972. Drug flashbacks: reported frequency in a military population. Am. J. Psychiatry 129, 751—755.

Stanton, M.D., Mintz, J., Franklin, R.M., 1976. Drug flashbacks. II. Some additional findings. Int. J. Addict. 11, 53—69.

Strassman, R.J., 1984. Adverse reactions to psychedelic drugs: a review of the literature. J. Nerv. Ment. Dis. 172, 577—595. Tennant, F.S., Groesbeck, C.J., 1972. Psychiatric effects of hashish. Arch. Gen. Psychiatry 27, 133—136.

Thurlow, H.J., Girvin, J.P., 1971. Use of antiepileptic medication in treating ‘flashbacks’ from hallucinogenic drugs. CMAJ 105, 947— 948.

Ujike, H., Takaki, M., Nakata, K., Tanaka, Y., Kodama, M., Fujiwara, Y., Sakai, A., Kuroda, S., 2002. CNR1, central cannabinoid receptor gene, associated with susceptibility to hebephrenic schizophrenia. Mol. Psychiatry 7, 515—518.

Ungerleider, J.T., Fisher, D.D., Fuller, M., 1966. The dangers of LSD: analysis of seven months’ experience in a university hospital’s psychiatric service. J. Am. Med. Assoc. 197, 109—112.

J.H. Halpern, H.G. Pope, Jr / Drug and Alcohol Dependence 69 (2003) 109118 —119

Weil, A.T., 1970. Adverse reactions to marijuana: classification and suggested treatment. N. Engl. J. Med. 282, 997—1000.

Welpton, D.F., 1968. Psychodynamics of chronic lysergic acid diethylamide use. J. Nerv. Ment. Dis. 147, 377—385.

Wentworth-Rohr, I., 1970. Marijuana flashback: a clinical note. Psychother. Theory Res. Pract. 7, 236—237.

Wesson, D.R., Smith, D.E., 1976. An analysis of psychedelic drug flashbacks. Am. J. Drug Alcohol Abuse 3, 425—438.

Wikler, A., 1954. Clinical and electroencephalographic studies on the effects of mescaline, N-allylnormorphine and morphine in man. J. Nerv. Ment. Dis. 120, 157—175.

Woody, G.E., 1970. Visual disturbances experienced by hallucinogenic drug abusers while driving. Am. J. Psychiatry 127, 683—686.

Worarz, N., 1993. ‘Ecstasy’-induced psychotic depersonalization syndrome. Nervenarzt 64, 478—480.

Yager, J., Crumpton, E., Rubenstein, R., 1983. Flashbacks among soldiers discharged as unfit who abused more than one drug. Am. J. Psychiatry 140, 857—861.

Young, C.R., 1997. Sertraline treatment of hallucinogen persisting perception disorder. J. Clin. Psychiatry 58, 85.

Zeidenberg, P., 1973. Flashbacks. Psychiatr. Ann. 3, 14—19. —Preceding unsigned comment added by 75.3.118.216 (talk) 02:57, 24 October 2007 (UTC)

[edit] Hippo rubbish...

Someone has sabotaged this page with some rubbish about hippos... Please can someone with the relevant knowledge correct it...

Thanks —Preceding unsigned comment added by 222.123.153.94 (talk) 22:26, 9 June 2008 (UTC)