drug_policy/heath.html

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Lair of the infamous tms: Drug Policy, heath

Article 3951 of talk.politics.drugs: Xref: wam.umd.edu alt.drugs:20287 talk.politics.drugs:3951 Path: wam.umd.edu!haven.umd.edu!darwin.sura.net!udel!wupost!zaphod.mps. ohio-state.edu!cis.ohio-state.edu!pacific.mps.ohio-state.edu!linac!att! news.cs.indiana.edu!hagerp@iuvax.cs.indiana.edu From: hagerp@iuvax.cs.indiana.edu (Paul Hager) Newsgroups: alt.drugs,talk.politics.drugs Subject: My critique of Drug-Free Indiana's use of Heath study Keywords: Heath, Drug-Free Indiana Message-ID: <1991Oct5.223302.11429@news.cs.indiana.edu> Date: 6 Oct 91 03:32:35 GMT Organization: Computer Science, Indiana University Lines: 135 Following is an excerpt from a letter that I sent to Jennifer Stabb of Drug-Free Indiana that critiqued the information on marijuana that they were disseminating. This is the section that deals with the Heath study. ------------------------excerpt follows----------------------- Dr. Robert Heath The "Drug Awareness Information Newsletter" entitled "Why Marijuana is not a Soft Drug" by Biernson and Moulton contains a presentation of work done by Robert Heath that purports to show that long-term, heavy use of marijuana leads to brain damage. Here's what they say about the "world renowned" work of Dr. Heath: "The following is a _typical_ [emphasis mine] experiment performed by Dr. Heath. For 6 months a monkey smoked the equivalent (for a human) of 1.5 joints per day. The monkey was allowed to recover for 6 months, and then was sacrificed. Brain waves were measured from electrodes embedded in the brain. The brain waves became severely distorted after 2 months of smoking, and remained severely distorted until the monkey was sacrificed, 6 months after smoking had stopped." The newsletter goes on to describe the "serious damage" found in the brain of the autopsied monkey. The "brain wave" anomalies Heath apparently claims to have found do not comport with studies done of human subjects (e.g., see "Marijuana, Memory, and Perception" by Dornbush, Fink, and Freedman, 1971), which have shown that cannabis increases alpha waves (often associated with a meditative or creative state). This effect lasts only as long as the cannabis intoxication. No lasting effect has ever been scientifically validated. The source quoted by Biernson and Moulton is not an authoritative scientific source nor the good Dr. Heath himself; it is Peggy Mann, author of a lurid bit of propaganda called "Pot Safari". The writers of these anti-marijuana propaganda books borrow from each other and purvey myths and bad science in an unending roundelay. The books actually have a lot in common, both structurally and intellectually, with pseudo-scientific books dealing with UFOs or the Bermuda Triangle. Before I give you the straight dope on Dr. Heath, I'll share with you a typical example of one of the propaganda books. This one is "Marihuana Today" by George K. Russell. "Heath demonstrated with objective measurements of brain wave patterns that the intake of less than two marihuana cigarettes a week for three months (a total of only 20 marihuana cigarettes!) caused serious, and quite possibly permanent, alteration of brain function in these experimental animals. "In these tests, one _group_ [emphasis mine] of animals was made to inhale cannabis smoke three times daily, five times a week, for six months (heavy dosage level); a second _group_ [emphasis mine] inhaled somewhat less than two marihuana cigarettes a week for six months (moderate dosage); a third _group_ [emphasis mine] received daily intravenous injections of delta-9-THC for six months. Control _animals_ [emphasis mine] received cannabis smoke devoid of THC. Brain wave patterns were monitored regularly during the six month test period." The words I italicized were in order to emphasize that Mr. Russell is deliberately misleading the reader. You see, each of the "groups" was actually a group of one. Here is what the Institute of Medicine, "Marijuana and Health" had to say about Heath: "[descriptions of brain alteration] These changes appear dramatic but they must be interpreted with caution. The three studies are based principally upon examination of two limited brain areas in three treated monkeys, two receiving marijuana smoke and one intravenous delta-9-THC; a fourth treated animal was added to the last study and more brain areas were analyzed in it (Heath et al., 1980). Further, although the material was evaluated 'doubleblind' after electron micrographs had been made, it would appear that fixation, tissue preparation, and photography were carried out before these safeguards against bias were applied. It is possible that unknown but systematic differences occurred between experimental and control animals in fixation and preparation fixation and preparation of tissue or in selection of samples for micrography. In addition, it should be noted that at least one of the changes noted, clumping of vesicles (Harper, et al., 1977) is a normal variant in the synaptic morphology of the axon terminals in mammalian brain (Sipe and Moore, 1977) and does not represent a pathological change. Also, these studies have not been replicated and, because the basis of the study for interpretation is such a limited sample, it is concluded that no definitive interpretation can be made at this time. However, the possibility that marijuana may produce chronic, ultra-structural changes in the brain has not been ruled out and should be investigated." If you are used to reading scientific papers, you will note that Dr. Heath and his co-workers don't come out looking very good in the above assessment. He didn't eliminate bias and his experimental sample was inadequate. He failed to realize that some of the "abnormality" he found was actually "normal". Though couched in the detached, objective language of the scientist, the report makes clear that the Institute of Medicine panel didn't think very much of Dr. Heath's work. And, they could have really slammed Heath, had they been so inclined. It turns out that another area of systematic experimental bias could have been described. The smoke inhalation studies failed to control for carbon monoxide. This, by the way, explains the anomolous result of the heavy and moderately dosed monkeys showing no apparent dose response to THC. ("Dose response" means an effect that correlates with the dosage such that the greater the dose, the greater the response.) All in all, Heath's work is so flawed that it is of essentially zero value in assessing marijuana health risks. In sharp contrast with Heath's findings are two human studies that showed no brain damage or atrophy at all (Co, Goodwin, et al., "Absence of cerebral atrophy in chronic cannabis users", JAMA, 1977 and Kuehnle et al., "Computed tomographic examination of heavy marijuana smokers", JAMA, 1977). None of the material I received references these studies. Why? -----------------------excerpt ends------------------------ -- paul hager hagerp@iuvax.cs.indiana.edu "Some men think the Earth is round, others think it flat; it is a matter capable of question. But, if it is flat, will the King's order make it round? And if it is round, will the King's command flatten it?" --from _A_Man_for_All_Seasons_ by Robert Bolt

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