Even claims about addiction mix up physical and psychological addiction, with many people unaware that what appears to be a physical addiction is really a psychological one. Also, according to a few studies, even users' claim about lack of appetite and poor nutrition don't hold up when addicts are in environments where the drug and food is free. I could be wrong about this, since the research I read was from the early 90s when I took a mandatory course on drugs and health -- required for anyone who wants to teach in the public schools. But from what others are saying, I don't think any new research has emerged to counteract a large body of literature on the topic.
Speaking of the sociology of drugs, who did the famous study that also showed that addicts (and I don't recall which drugs they were testing, but i thought it was morphine) withdrawal symptoms were very much psychological. When the addict inevitably asked for a fix when they were forced to go cold turkey, they were appeased with sugar pills, but the addicts thought it was morphine. Withdrawal symptoms vanished. IIRC, it was a study in England, in the 30s or 40s.
Anyway, here's the research snippet:
"The classical clinical study of the effects of prolonged opiate use on the human body was performed in the narcotics wards of the Philadelphia General Hospital during the 1920s, under the impeccable auspices of the Committee on Drug Addictions of the Bureau of Social Hygiene-a Rockefeller-financed agency-and of the Philadelphia Committee for the Clinical Study of Opium Addiction. In charge were two physicians, Drs. Arthur B. Light and Edward G. Torrance, assisted by a biochemist, Dr. Walter G. Karr, and by Edith G. Fry and William A. Wolff. The results were published by the American Medical Association in the A.M.A. Archives of Internal Medicine (1929), and in a book, Opium Addiction.6 The findings of this study are still cited as authoritative in medical textbooks.
In all, 861 male addicts-80 percent of them addicted to heroin and the others to morphine or other opiates-participated in various phases of this study. Most of them were between twenty and forty years of age. They came to the hospital more or less voluntarily (in some cases, no doubt, to escape arrest) for the stated purpose of being "cured." Most of them were criminals and most of them were poor; then as now, affluent addicts did not go to a city hospital for treatment. Here is the broad general conclusion which Dr. Light and his associates reached:
The study shows that morphine addiction is not characterized by physical deterioration or impairment of physical fitness aside from the addiction per se. There is no evidence of change in the circulatory, hepatic, renal or endocrine functions. When it is considered that these subjects had been addicted for at least five years, some of them for as long as twenty years, these negative observations are highly significant.7
Details of the study were equally striking. For example, the narcotics addict is popularly portrayed as lean, gaunt, emaciated. A subgroup of about 100 addicts out of the 861 in the Philadelphia study was maintained on adequate doses of morphine and intensively examined and tested while thus maintained. Only four of the 100 were grossly underweight - emaciated. Six of the 100 were grossly overweight-obese. The group as a whole weighed within two-tenths of one percent of the norm for their height and age, as determined by Metropolitan Life Insurance Company standards. Yet these addicts before hospitalization had been taking on the average 21 grains of morphine or heroin per day8 -more than 30 times the usual dose of the New York City street addict in 1971.
The explanation for the weight findings, which could hardly be more normal, is quite simple. The addicts in the Philadelphia study had ready access to both hospital food and hospital morphine. Under these conditions, they ate well and thrived. The emaciated addict usually described in other studies is one who starves himself to save money for black market drugs-an ordeal he is able to bear more easily because of the tranquilizing effect of the drugs. The Philadelphia study established that addicts eat like anyone else when both food and drugs are readily available.
The addict is also customarily portrayed as sallow-complexioned. But, Dr. Light and his associates noted, "this change in color was practically always present in patients who lived a rather unhygienic, sedentary life. On the other hand, the skin of those who followed healthy outdoor occupations had the color of excellent health.'"9
The Philadelphia group did notice "a slight degree of anemia" in some of their addicts on admission. This may be present, they added, "when the addict is forced to live in poor hygienic surroundings [and] when all his funds are required to purchase the drug at the expense of sufficient nourishing foods." 10
Dr. Light and his associates confirmed that 60 percent of the Philadelphia addict group "exhibited a particularly high degree of pyorrhea and dental caries"-but "one must bear in mind that these people are notorious in their lack of care of the teeth and failure to consult a dentist." 11 Malnutrition may also have been a factor. Whatever the cause, there is no evidence that narcotics "rot the teeth." The 1956 British Columbia study also noted a high degree of tooth decay among imprisoned addicts -but found comparable decay in a comparison group of prisoners who were not addicted.12 Perhaps the chief effect of narcotics on the teeth is to enable an addict to bear toothaches uncomplainingly.
Many of the Philadelphia addicts showed chronically inflamed throats and an atypical blood-pressure change when they stood up after lying down. Both of these signs, the Philadelphia researchers noted, are to be expected in excessive cigarette smokers-and all of their narcotics addicts also smoked cigarettes excessively.13
A similar study made at Bellevue Hospital in New York City yielded similar findings. Dr. George B. Wallace summed up both studies: "It was shown that continued taking of opium or any of its derivatives resulted in no measurable organic damage. The addict when not deprived of his opium showed no abnormal behavior which distinguished him from a non-addict." 14
http://www.drugtext.org/library/reports/cu/cu4.html